The XML Files:
Development of XML/XSL Applications
Using WebSphere Studio Version 5
Introduces WebSphere Studio Application
Developer Version 5 XML tooling
A comprehensive guide to XML
support of WebSphere Family
Start-to-finish
application case studies
Osamu Takagiwa
Deena Hassan
Oliver Quixchan
Jagjit Singh
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International Technical Support Organization
The XML Files: Development of XML/XSL
Applications Using WebSphere Studio Version 5
December 2002
SG24-6586-00
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Note: Before using this information and the product it supports, read the information in
“Notices” on page ix.
First Edition (December 2002)
This edition applies to Version 5 of IBM WebSphere Studio Application Developer.
© Copyright International Business Machines Corporation 2002. All rights reserved.
Note to U.S. Government Users Restricted Rights -- Use, duplication or disclosure restricted by GSA ADP Schedule
Contract with IBM Corp.
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Notices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ix
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xi
The team that wrote this redbook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xi
Comments welcome. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
Part 1. Introduction to XML technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Chapter 1. XML overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 XML concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 XML business benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.1 Information sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.2 XML within an organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.3 XML in new innovations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4 Technical benefits of XML. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.5 XML history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.6 XML1.0 and 1.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.7 XSLT and Web applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.8 Web services and XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.9 XML, W3C, and IBM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1 XML Processor (parser) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.2 DTD and XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.4 XML namespaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.6 XPath. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.7 XML digital. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.8 XML query language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.9 XSLT compilers (XSLTC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
2.10 Java Architecture for XML Binding (JAXB) . . . . . . . . . . . . . . . . . . . . . . . 49
2.11 Cocoon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Part 2. XML technology in IBM WebSphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
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Chapter 3. Processing XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.1 XML applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.2 Xalan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.3 SAX2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.4 DOM level2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.5 JAXP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.2 Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.2.2 Relational database tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.2.3 XML tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.2.6 EJB development tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.2.7 Team collaboration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.2.8 Debugging tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.2.9 Performance profiling tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.1 XML perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.2 XML perspective editors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.2.1 XML editor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.2.2 DTD editor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.2.3 XSD editor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.2.4 XSL editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
5.3 Namespace support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.4 XPath support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.5 XSL debugger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5.6 Web services support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Chapter 6. RDB and XML integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
6.1 The SQL to XML wizards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
6.2 The XML to SQL wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
6.4 DB2 XML Extender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.4.1 XML Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
Chapter 7. Generators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
7.1 DTD <—> XSD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
7.2 XML <—> DTD/XSD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
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7.2.3 Create DTD/XSD files from XML. . . . . . . . . . . . . . . . . . . . . . . . . . . 149
7.4 JavaBeans from DTD/XSD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Part 3. XML application development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
8.2 Web services. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
8.3 Passenger List application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
8.3.1 Solution Outline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
8.3.2 XML in this application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
8.4 Enterprise JavaBeans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
8.5.1 XML in this application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
8.5.2 Technical overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
9.1 Passenger List application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
9.1.1 Creating the Web tier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
9.1.5 Generate XML file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
9.1.7 Testing the XSL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
9.1.8 Developing the servlet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
9.1.10 Compiling XSL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
9.2 Creating a Web service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
9.2.1 Create the database tier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
9.2.2 Generate DTD file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
9.2.3 Loading DTD into XML Extender . . . . . . . . . . . . . . . . . . . . . . . . . . 195
9.2.4 Creating DAD file using RDB to XML mapping . . . . . . . . . . . . . . . . 196
9.2.5 Create the Web Service from DADX file . . . . . . . . . . . . . . . . . . . . . 199
9.2.6 Test the Web Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
9.2.7 Modify passenger list application to use the Web Service . . . . . . . 208
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10.3.1 Creating the Web tier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
10.3.4 Retrieval function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
11.1 SQL to/from XML libraries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
11.2.1 Customer registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
11.3.2 XML Document format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
11.3.5 Retrieving a customer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
11.3.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
12.1 Manual deployment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
12.1.4 Installing the EAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286
12.1.5 Testing the application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
12.2 Publishing to a remote server (AEs) . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
12.2.3 Testing the application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
Part 4. Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
Appendix A. Installing WebSphere Studio Application Developer. . . . . 299
Things to do before installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
Installing Application Developer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
Selecting your workspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
Verifying the installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
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Things to do before installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
Hardware and software prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
Create groups and users. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
Install WebSphere Application Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
Locating the Web material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
Using the Web material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
Abbreviations and acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
Related publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
IBM Redbooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
Other resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
Referenced Web sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
How to get IBM Redbooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
IBM Redbooks collections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
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Notices
This information was developed for products and services offered in the U.S.A.
IBM may not offer the products, services, or features discussed in this document in other countries. Consult
your local IBM representative for information on the products and services currently available in your area.
Any reference to an IBM product, program, or service is not intended to state or imply that only that IBM
product, program, or service may be used. Any functionally equivalent product, program, or service that
does not infringe any IBM intellectual property right may be used instead. However, it is the user's
responsibility to evaluate and verify the operation of any non-IBM product, program, or service.
IBM may have patents or pending patent applications covering subject matter described in this document.
The furnishing of this document does not give you any license to these patents. You can send license
inquiries, in writing, to:
IBM Director of Licensing, IBM Corporation, North Castle Drive Armonk, NY 10504-1785 U.S.A.
The following paragraph does not apply to the United Kingdom or any other country where such
provisions are inconsistent with local law: INTERNATIONAL BUSINESS MACHINES CORPORATION
PROVIDES THIS PUBLICATION "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR
IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF NON-INFRINGEMENT,
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Some states do not allow disclaimer
of express or implied warranties in certain transactions, therefore, this statement may not apply to you.
This information could include technical inaccuracies or typographical errors. Changes are periodically made
to the information herein; these changes will be incorporated in new editions of the publication. IBM may
make improvements and/or changes in the product(s) and/or the program(s) described in this publication at
any time without notice.
Any references in this information to non-IBM Web sites are provided for convenience only and do not in any
manner serve as an endorsement of those Web sites. The materials at those Web sites are not part of the
materials for this IBM product and use of those Web sites is at your own risk.
IBM may use or distribute any of the information you supply in any way it believes appropriate without
incurring any obligation to you.
Information concerning non-IBM products was obtained from the suppliers of those products, their published
announcements or other publicly available sources. IBM has not tested those products and cannot confirm
the accuracy of performance, compatibility or any other claims related to non-IBM products. Questions on
the capabilities of non-IBM products should be addressed to the suppliers of those products.
This information contains examples of data and reports used in daily business operations. To illustrate them
as completely as possible, the examples include the names of individuals, companies, brands, and products.
All of these names are fictitious and any similarity to the names and addresses used by an actual business
enterprise is entirely coincidental.
COPYRIGHT LICENSE:
This information contains sample application programs in source language, which illustrates programming
techniques on various operating platforms. You may copy, modify, and distribute these sample programs in
any form without payment to IBM, for the purposes of developing, using, marketing or distributing application
programs conforming to the application programming interface for the operating platform for which the
sample programs are written. These examples have not been thoroughly tested under all conditions. IBM,
therefore, cannot guarantee or imply reliability, serviceability, or function of these programs. You may copy,
modify, and distribute these sample programs in any form without payment to IBM for the purposes of
developing, using, marketing, or distributing application programs conforming to IBM's application
programming interfaces.
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Trademarks
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other countries, or both:
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The following terms are trademarks of International Business Machines Corporation and Lotus Development
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The following terms are trademarks of other companies:
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United States, other countries, or both.
Java and all Java-based trademarks and logos are trademarks or registered trademarks of Sun
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Other company, product, and service names may be trademarks or service marks of others.
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Preface
In today’s technology, XML is becoming a key piece of software infrastructure.
The main idea is extremely simple. It is a language like HTML and is text based,
but is rigidly enforced, and therefore, can be built upon easily. XML documents
may use a Document Type Definition (DTD) or an XML Schema. XML was
designed to describe data and to focus on the data, unlike HTML, which was
designed to display data. It was created to structure and store data.
This book is separated into three parts:
Part one introduces the eXtensible Markup Language (XML) and how it can be
used in today’s technology and provides the reader with an opportunity to learn
about the processing of XML documents.
Part two contains an introduction to the concepts behind WebSphere Studio
Application Developer, and an overview of the features of the various members
of the WebSphere Studio family of tools including wizards and generators.
Part three, we provide an overview of Web Services and Enterprise JavaBeans
capabilities of Application Developer. We also develop several variations of Web
applications that works with RDB, Web Services, or Enterprise JavaBeans.
The team that wrote this redbook
This redbook was produced by a team of specialists from around the world
working at the International Technical Support Organization, San Jose Center.
Osamu Takagiwa is an advisory IT specialist at the International Technical
Support Organization, San Jose Center. He writes extensively and teaches IBM
classes worldwide on all areas of application development. Before joining the
ITSO 1.5 years ago, Osamu worked in IBM Japan as an I/T specialist.
Deena Hassan is an IT specialist at the Cairo Technology Development Center
(CTDC) of IBM Egypt. She has experience in application development,
particularly in the e-commerce field. She holds a degree in Computer Science
from the American University in Cairo, and is about to recieve her master’s
degree in the field of Artificial Neural Networks. Her areas of expertise include
Enterprise Java programming and e-commerce solutions.
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Oliver Quixchan is an e-business consultant from Guatemala. He holds a BS in
Computer Science from Universidad Francisco Marroquin, Guatemala. He has
experiece in application development, Web-oriented solutions using J2EE and
WebSphere software platform, banking software development, and middleware
design. His areas of expertise include WebSphere Application Server,
WebSphere Host Pblisher, XML, J2EE.
Jagjit Singh is an IT architect with IBM Global Services, Australia. He has 14
years of experience in application development and architecture. He holds a
master’s degree in Computer Science from the University of New South Wales,
Sydney, Australia. His areas of expertise are in e-business, middleware, and
Internet design and implementation on Windows NT and UNIX environments.
Thanks to the following people for their contributions to this project:
Maritza Marie Dubec
Emma Jacobs
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Preface
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Part 1
Introduction to XML
technology
Part one introduces the eXtensible Markup Language (XML) and how it can be
used in today’s technology. This highlights the XML Processor and parser
shipped with Websphere Application Developer.
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XML overview
“I think we should shoot for a goal within the developed countries of having
Internet access as complete as telephone access within a fixed number of
years. It will do as much as anything else to reduce income inequality.”
Bill Clinton, President of the United States of America, November 21, 1999
This chapter introduces the eXtensible Markup Language (XML) and how it can
be used in today’s technology. It explains its background since it appeared on the
horizon, its evolution and its benefits both within the industry and also its use
within an organization. It discusses two innovations that have gained firm ground
among the many that are being put onto the e-business market over the last few
years. It also lists IBM contributions to the World Wide Web (W3C) group.
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1.1 XML concepts
In today’s technology, XML is starting to becoming a key piece of software
infrastructure. The main idea is extremely simple. It is a language like HTML and
is text based, but is rigidly enforced, and therefore, can be built upon easily. XML
documents may use a Document Type Definition (DTD) or an XML Schema.
XML was designed to describe data and to focus on the data, unlike HTML which
was designed to display data. It was created to structure and store data.
1.2 Background
The Internet has had amazing growth during the last 8 years. However, in the
last four years, its usage has increase exponentially. In the first 4 years, its
foundations were laid, and in the later 4 years, a number of technologies have
evolved around it. Today, it is in the mainstream of life, and everyday, every
talk revolves around its usage. Nowadays, advertising mandates that a Web
page address be displayed and e-mail is considered official documents.
This growth has been fueled by many factors. The cost of personal computers
has decreased dramatically, network technologies are more widespread and
cheaper, schools are emphasizing computer literacy at an early age. Its ease of
use has been its biggest contributor. Access to the Internet is as easy as logging
through the phone line and the local area network. Computer education is now
part of the school curriculum at the primary level, so that today’s youngsters do
not lose out on the this new revolution.
Tim Berners-Lee, who leads the World Wide Web Consortium (W3C), the
inventor of HTML and HTTP, could not have envisaged this growth. Even,
computer giants like IBM and Microsoft had to realign their technical and
business philosophies to cater for the explosive growth. To not follow, meant to be
left behind. It would be true to say, we cannot envisage what the Internet will
bring in the next five years, only to say that there will be new ways we will be
doing business and enjoying leisure.
This ability to manage large amount of simple and complex data in many forms,
without limitations, and display in a readable format, can be based for this
universal data format. As we know, this can be provided by the eXtensible
Markup Language (XML).
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1.3 XML business benefits
The benefits of a common base upon which the technical world can build layers
upon layers of technical innovation are enormous. This will only be possible if this
standard has been agreed to by all.
XML has three main applications:
Sharing of information: The main problem integrating data between any two
business organizations is the interface between them. If they can at least agree
upon the standard of their common meeting point and its usage, they can build
upon this to start building their applications. If there is already an existing
interface or infrastructure provided by industry or government standard or
infrastructure, the business cost of developing it is extinguished.
Storage, transmission and interpretation of data: If the storage of information
is adaptable to many mediums, its cost will be driven to the lowest cost of all
mediums. XML is based on text, which obviously is accepted by all. It can be
read. Its storage is cheap, compared to the storage requirements of graphics.
And because the size of this text based object is small, its transmission, not
withstanding cost, is cheap as well. And because it is commonly accepted, since
it adheres to world wide standards, it can be easily interpreted.
Security: With the explosion of confidential information being transmitted across
the Internet, there is now a need for sophisticated levels of security. Companies
need to protect their documents and e-mail, banks need to allow their depositors
to download their accounts and merchants need to be available their customers
to enter their credit card details without compromising their security and privacy.
The more secure the transmission medium, the more confidentiality it provides,
the more it can be used to advertise a competitive advantage. With the evolution
of XML digital signatures, the ability to protect or hide parts of a document, while
sitting on a PC, server or mainframe, now covers up a security patch.
Speed and amount of content delivery: With the rapid evolution of network
technologies, speed and delivery of any object has gained importance. Network
companies now advertise download times of movies and CDs. Again, the first
companies discovering the abilities of delivering something at an increasing
speed without compromising their content will gain the competitive advantage.
1.3.1 Information sharing
XML has been readily accepted by the technical world because of its simplicity.
The benefits of having a common format to share information between any two
organization are obvious. Technologies and standards have been built upon
XML. Consortiums and business organizations have developed industry wide
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XML formats and standardization. Examples of these are inter-bank payment
between banks, insurance companies and trading agencies, supply-chains
between manufacturers, distributors and retailers, battlefield information between
soldiers, satellites and defence analysts.
In December 2000, the United Nations Centre for Trade Facilitation and
Electronic Business (UN/CEFACT) and the Organizations for the Advancements
of Standard Information Standards (OASIS) came together to initiate a project to
standardize XML specifications for business. This initiative called the Electronic
Business XML (ebXML) developed a technical framework that enabled XML to
be utilized for all exchange of all electronic business data. The main aim of
ebXML was to lower the cost and difficulties, focusing on small and medium
sized business and developing nations, in order to facilitate international trade.
Another example, BizTalk, is an initiative supported by Microsoft, SAP, and
Boeing, among other major vendors. However, BizTalk is not a standard, more of
an community of users. Its aim to enable consistent adoption of XML to ease
use, and therefore, easily adopt electronic commerce and application integration.
1.3.2 XML within an organization
With the emergence of Customer Relation Management (CRM) and Enterprise
Architecture Integration (EAI), customer oriented organizations have
re-engineered their systems to provide a whole new experience for the
consumer.
CRM and EAI involve bringing together a multitude of applications and systems
from multiple vendors to behave as a coordinate whole. The common thread
between all these applications is XML. Imagine trying to integrate information
from billing histories, customer personal information and credit histories,
distribution systems, and workforce management systems; and then displaying
them using browsers, databases, processes, and workflow systems on a variety
of technical platforms like mainframes, PCs, and medium sized servers. All this
information can be shared by using XML, because it is a versatile, powerful, and
flexible language. It has the ability of describing complex data. It is also
extensible, allowing applications to grow and develop without architectural
re-engineering.
Needless to say, IBM has used XML in all its new tools. IBM’s mainstay
applications: WebSphere Studio, DB2, and WebSphere Application Server are
based upon XML with their extensibility being a major advantage.
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1.3.3 XML in new innovations
There have such a large number of innovations based on XML, they are too
numerous to list. New ideas are now based in XML. Entrepreneurial companies
now cannot avoid XML and its standards.
Voice XML
In October, 2001, the World Wide Consortium (w3C) announced the first release
of a working draft for the Voice Extensible Markup Language (VoiceXML).
VoiceXML has these purposes among others:
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It will hide designers and developers from low-level platform specific details.
It will promote portability across implementation platforms.
It will be a common language for platform providers, development tool
providers and content providers.
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It would provide features to support complex dialogs, yet be easy to use for
simple interactions.
It is designed to cater for audio dialogs that would feature digitized audio,
speech recognition, telephony and synthesized speech. Its goal would be to
deliver advantages of Web-based development and context delivery for
interactive voice response applications.
Scalable Vector Graphics
Scalable Vector Graphics (SVG) is an XML based language for describing
two-dimensional graphics. Its main use is in Geographical Information Systems
(GIS) where travel maps, council boundaries, forest fires and natural disasters
can be processed and displayed independently of technical platforms. It will be
able to integrate with non-GIS software, and also allow graphic elements to
non-graphic.
The benefits of this new XML derivative are not difficult to comprehend. It uses
are many. For example, insurance companies can estimate and forecast natural
disaster claims; and scientists can study environmental impacts, and local and
federal governments for city and town planning.
1.4 Technical benefits of XML
Fundamentally, the basics of XML have not changed. What has changed is the
extent XML is being used today, and how it is incorporated into technologies for
the future. XML offers many benefits, some of which are stated below.
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Acceptability of use for data transfer
XML is not a programming language. It is a standard way of putting information in
a format that can be processed and exchanged across hardware devices,
operating systems, software applications, and the Web. It has become such a
common medium of data that it enables the transmission and retrieval, and
storage of information over the Internet across company boundaries, making it a
natural choice for data management for e-business transactions.
Uniformity and conformity
The inability of two computer systems or applications to talk to each other is
always a challenge. When two applications are integrated, the business and
technical experts must decide either to integrate the two systems, or to
re-architect the applications. If data from both applications, conform to a format
and is easily transformed from one to another, development costs can be
reduced. If this common format could be developed upon and is accepted
industry-wide, then interfacing the applications to other applications is less
costly.
Simplicity and openness
Information coded in XML is visually read and accepted, because it can be easily
processed by computers, XML is widely accepted by major vendors in the
computing world. Microsoft has indicated that it will use XML as the exchange
format for its Microsoft Office software suite. Both Microsoft's and Netscape's
Web browsers support XML.
XML has garnered interest because it is very simple to understand, implement,
and use. It follows the Pareto principle, a 80/20 solution, meaning it supplies
about 80 percent of the functionality of competing technologies with perhaps 20
percent of the effort required to build Enterprise-level solutions.
XML is not a total solution for every problems in e-business, but has made, and is
making significant inroads in communications between old computer programs.
That means these old programs last longer, saving money and time, which are
important when both are so precious to the bottom line.
Separation of data and display
Separation of data and its display is not a new paradigm in the computing world.
In the last few years, application designers have raised the concept of the
Model-View-Controller (MVC) approach to building applications. There are many
reasons for this. Firstly, without separation of data, re-use of that data in multiple
user interfaces would be difficult. Web sites have evolved radically over the last 8
years. Evey year, Web sites have to be upgraded to compete for consumer
attention. They have to have better attention getting displays and response times.
If the data had to be re-hashed everytime an upgraded to the Web site was
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required, the development cost would rise. However, if the data could be re-used
or built upon, there would be a re-development savings.
Imagine a navigation system used by consumers to move from one place to
another. This system would have street maps, yellow pages information, local
attractions and other information. If this information has to be displayed on a Web
browser, personal device assistant (PDA) or a mobile phone, it would be a major
development costs if we had to develop three separate data access systems and
three data presentation systems. However, if we develop one data access
systems, we also need to create three data presentation files for each system,
which transforms XML using the XSLT transformation feature.
Extensibility
HTML has a major problem in that it is not extensible. It has been enhanced upon
by the different software vendors. These enhancements have not been
co-ordinated, and therefore, have become non-standard. It was never designed
to access data from databases. To overcome this deficiency, Microsoft built
Active Server Pages (ASP) and Sun produced Java Server Pages (JSP).
As the name implies, XML was designed from the beginning to allow
extensions.
Industry acceptance
XML has been accepted by widely by the information and computing Industry. It
is based on common concepts. As time goes on, a large number of XML tools
will emerge from both existing software vendors and XML startup companies.
It is readable by every operating systems, because it is in ASCII text. This
implies that it can be seen by any text editor or word processor.
The tree-based structure of XML is much more powerful than fixed-length
data formats. Because objects are tree structures as well, XML is ideally
suited to working with object-oriented programming.
1.5 XML history
The history of XML is really the history of another system: Standard
Generalized Markup Language or SGML. XML is actually just a subset of
SGML, and SGML has been around for many years. In fact, SGML dates back
to the late 60s and the work of an IBM employee Charles Goldfarb. Goldfarb
was developing a system to share documents, and together with two of his
colleagues, Edward Mosher and Raymond Lorie, he put together a markup
language called Generalized Markup Language (GML). (Of course, GML
really stands for Goldfarb, Mosher, and Lorie, who invented it.)
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GML also drew on work by William Tunnicliffe and Stanley Rice on building a
generic coding system, which was done under the auspices of the Graphic
Communication Association.
GML formed the basis of many IBM documentation systems including Script
and Bookmaster. Later developments led to SGML, which became an ISO
standard in 1986. SGML has had a great deal of success, but unfortunately, it
has mainly been limited to large corporations and government departments.
The reason was that SGML required a major investment, and so, only large
organizations had the resources to achieve the benefits of SGML. For more
information on SGML and its history, read The SGML Handbook, ISBN
0198537379.
In 1996, W3C sponsored a group of SGML experts to define a markup language
with the power of SGML and the simplicity of HTML. The team abandoned the
non-essential and cryptic parts of SGML. The remainder was a cut-down
specification of 26 pages on XML. SGML had a specification of 500 and more
pages. The new specification, however, managed to conceptualize the main
ingredients of the older language.
Over the following years, XML evolved with the help of developers having similar
problems. At that time, Chemical Markup Language (CML) and MathML were
being formulated, and the eTensible Linking Language project was gaining
speed. Finally in 1998, the W3C approved Version 1.0 of the XML specification
and a new language was born.
Since the end of 1997, XML has grown quickly under the leadership of W3C,
and in September 1999, W3C announced that XML activity was entering its
third phase: Phase one built the base technology; phase two created
stylesheets and namespaces; and phase three will endeavor to finish the
ongoing work and introduce new specifications for an XML query standard.
Since then, as we know now, the usage of XML has exploded. We can only say
that its application will continue for a long while to come. Since 1997, we have
seen a multitude of tools evolving, including parsers, transformers, protocols,
standards, and business-to-business integration.
1.6 XML1.0 and 1.1
The working draft for XML 1.1 was published on W3C Web pages in April 2002.
XML 1.1 was formerly known as XML Blueberry.
The XML 1.0 specifications was based on the Unicode Standard. However, the
Unicode standards have evolved from version 2.0 to 3.1 and beyond. XML 1.0
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relied on the standard for character specifications. Characters that are not
present in Version 2.0 would probably have be used in XML documents and
character data. Developers would have developed workarounds for characters
that were not supported in Unicode Version 2.0. These characters are not
allowed in XML names such as element type, names, and attribute names, just to
name a few. Also, some characters that should have been permitted in XML 1.0,
but were not due to oversights and inconsistencies in Unicode 2.0.
The philosophy for names has been reversed since XML1.0. XML1.1 names
have been designed such that everything that is not forbidden is permitted. In
XML1.0 the philosophy was everything that was not permitted was forbidden. For
example, under XML1.0, if only ‘a’, ‘b’, ‘c’, ‘d’ and ‘e’ were allowed as names, that
was that could be used. In XML 1.1, we could say that we would not allow ‘a’ and
‘b’. Therefore, we could use ‘b’, ‘c’, ‘e’, ‘f’, ...’g’, ...’$’, etc. As Unicode grows past
Version 3.1, changes to the XML can be avoided if nearly all characters are
allowed. This will allow any kind of characters in a name.
XML1.0 discriminates against conventions used on IBM and IBM-compatible
mainframes. XML documents on mainframes and not plain texts. Now, the
Unicode line separator, #x2028, is also supported.
A new version of XML is being created, rather than a set of errata, because the
changes affect the definition of well-formed documents. XML Processors will
recognize XML 1.1 documents from XML 1.0 documents by the declaration at the
start of each document.
For more details, visit W3C Web site:
1.7 XSLT and Web applications
Extensible Stylesheet Language Transformations (XSLT) is designed to
transform XML data into some other form. The most common form the
transformation occurs to is HTML. Transformation to HTML is the final step
before the user sees the Web page.
The main problem with HTML is its unorganized implementation. It evolution was
driven mainly by extreme competition between Netscape and Microsoft. Each
vendor tried to gain market share by its own browser specific tags and varying
support for standards. To create a HTML page that would work on all browsers,
developers therefore had to restrict themselves to tags that were generic to all
browsers. A different approach would be to maintain a HTML page for each kind
of browser.
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Presently, Web services theoretically need to support a multitude a browsers.
The data sent to the browsers would be common to all, but the presentation of
the data could be dependent on the browser. In effect, the presentation of the
data could be PDA or even a mobile phone.
An XSLT stylesheet is a XML document. A XSLT processor transforms one or
more XSLT stylesheets. Typically, in a Java and XSLT based Web application,
Java is used to access the data from the database. XML data is then generated
dependent on the data. With the latest release in database technologies, some
databases have now the ability to export the data into XML. However, usually
programmers write the code to extract the data and convert it into XML.
The processes takes the XML file as one input, and the XSLT stylesheet as the
second input, and produces a third output, which is usually HTML, but could be
another XML document. The XML file has the data to be presented while the
XSLT stylesheet details the logic of how the output data is to be presented.
Web Tier
Web Browser
Presentation Data
HTML
XML Data
XSLT
Processor
Database
XSLT StyleSheet
Presentation Logic
Figure 1-1 XSLT and Web applications
A Web application is an application with its presentation layer (or user interface)
on the World Wide Web. These applications display graphics, text, and
animation. It tends to be custom made and uses a host of technologies like
browsers, databases, and programming languages to name a few. Because of
the number of technologies and the skills sets required of its designers and
developers, Web applications have to be modular. While the graphic designer
concentrates on the HTML user interface, the database programmer focuses on
extracting the correct data. A Java programmer might be working on the Web tier.
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XSLT has become a critical part of Web applications, because it allows versatility
in the presentation logic. W3C has published a working draft for XSLT Version 2.0
and XML Path Language (XPath) Version 2.0 in April 2002. The later had a major
IBM involvement.
1.8 Web services and XML
Web services have gained prominence in the last three years. They are the new
middleware that will glue all kinds of disparate applications from different
vendors. Presently, there are a few major vendors touting middleware: TIBCO,
BEA eLink/Tuxedo and IBM’s MQ-series. Web services on the other hand are not
proprietary. They are self-contained, modular applications, self explanatory
applications that are published on the Web. They provide functions that
encapsulate anything from single functions to complex business functions. An
example of a simple function may be a calculator, spreadsheet, or a tutorial. An
example complex functions could be the processing of a tax return, stock quotes,
or processing credit card transactions. Once this Web service has been
deployed, anyone (be it another application or Web service) would be able to
locate and invoke it.
When we discuss Web services, we involve a few components:
Simple Object Access Protocol (SOAP) is an XML-based protocol that allows
applications to invoke applications provided by service provides anywhere on the
Web. It is supported by HTTP, and therefore, can be run on the Internet without
any new requirements over existing infrastructure. It is independent off any
programming language and component technology, and is object neutral. It is
also independent of operating systems.
Universal Description Discovery and Integration (UDDI) is a specification for
Web registries of Web services. Web users locate and discover services on a
UDDI-based registry. There are registries of services distributed over the
Internet, and these registry of services are described in a common XML format
or schema. For a common format, searching and analysis of applications would
be made much easier. A UDDI registry has been made available from IBM’s
alphaWorks Web site, and supports users in various department- or
company-wide scenarios.
Web Services Description Language (WSDL) is a language that is used to
describe a service to the world. The definition of WSDL is:
“WSDL is an XML format for describing network services as a set of
end-points operating on messages containing either document-oriented or
procedure-oriented information. The operations and messages are described
abstractly, and then bound to a concrete network protocol and message
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13
format to define an endpoint. Related concrete endpoints are combined into
abstract endpoints (services). WSDL is extensible to allow description of
endpoints and their messages regardless of what message formats or
network protocols are used to communicate, however, the only bindings
described in this document describe how to use WSDL in conjunction with
SOAP 1.1, HTTP GET/POST, and MIME.”
UDDI Registry
UDDI Registry
Another
Service
Service
Broker
Broker
publish with
WSDL
find thru
WSDL
first bind, then invoke
Service
Provider
Service
Requester
SOAP
Application by
Web Service
Client
Figure 1-2 Interaction of Web services
1.9 XML, W3C, and IBM
The World Wide Web Consortium (W3C) creates Web standards for the Internet.
It formed a Web service activity group in January 2002. The goal of the Web
service activity is to develop technologies in order to bring Web services to their
full potential. It consists of three working groups: Web Services Architecture
Working Group, XML Protocol Working Group, Web Services Description
Working Group.
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The W3C regularly publishes technical reports and publications. IBM has made
major contributions to the W3C. A list of publications where IBM researchers
have been involved in follows. The list is not exhaustive.
Recommendations
“A recommendation is work that represents consensus within W3C and has the
director's stamp of approval. W3C considers that the ideas or technology
specified by a recommendation are appropriate for widespread deployment and
promotes W3C's mission.”
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Extensible Stylesheet Language (XSL) Version 1.0
Synchronized Multimedia Integration Language (SMIL 2.0)
Candidate recommendations
“A candidate recommendation is work that has received significant review from
its immediate technical community. It is an explicit call to those outside of the
related Working Groups or the W3C itself for implementation and technical
feedback.”
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XML encryption syntax and processing
Decryption transform for XML signature
Working drafts
“The following working drafts have been submitted for review by W3C members
and other interested parties. These are draft documents and may be updated,
replaced, or made obsolete by other documents at any time. It is inappropriate to
use W3C working drafts as reference material or to cite them as other than work
in progress.”
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SOAP Version 1.2 Part 1: Messaging framework
SOAP Version 1.2 Part 2: Adjuncts
Voice Extensible Markup Language (VoiceXML) Version 2.0
XForms 1.0
XMl events
Working drafts in development
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XML protocol usage scenarios
XML protocol requirements
XML query use cases
XML Path Language (XPath) 2.0
XQuery 1.0: An XML query language
XQuery 1.0 formal semantics
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2
Technologies in XML
This chapter discusses some of the latest technologies being introduced in the
XML arena. Some of these have been around for the last three years or so, and
are undergoing enhancements and the others are fairly new.
The material is intended for introduction only, where detailed investigation of
each of these technologies is a subject by itself. The material forms a good
groundwork for concepts required in developing of many applications in
WebSphere Studio Application Developer. The following technologies are
discussed:
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XML Processor
DTD and XML Schema
CSS, XSLT and XSL
XLink, XPointer and XBase
XML Digital Signature
XML Query Language
XSLT Compilers (XSLTC)
Java Architecture for XML Binding
Cocoon
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2.1 XML Processor (parser)
An XML Processor can either be a validating or non-validating parser. Both kinds
of parsers report violations on an XML document. According to the XML 1.0
specification:
“Validating processors must, at user option, report violations of the
constraints expressed by the declarations in the DTD, and failures to fulfill the
validity constraints given in this specification. To accomplish this, validating
XML Processors must read and process the entire DTD and all external
parsed entities referenced in the document.”
Non-validating processors are required to check only the document entity,
including the entire internal DTD subset, for well-formedness. While they are not
required to check the document for validity, they are required to process all the
declarations they read in the internal DTD subset and in any parameter entity
that they read. This is done up to the first reference to a parameter entity that
they do not read; that is to say, they must use the information in those
declarations to normalize attribute values, include the replacement text of internal
entities, and supply default attribute values. Except when standalone="yes", they
must not process entity declarations or attribute-list declarations encountered
after a reference to a parameter entity that is not read, since the entity may have
contained overriding declarations.
From the definition above, a validating parser must read the entire DTD and
check the XML document against it. A non-validatiing parser may not need the
DTD must still check the XML against default values for attributes. Both parsers
check for the well-formedness of the document.
Most parsers can be run in validating and non-validating mode. Validating of XML
documents is crucial in the development and testing stage of the software
development life cycle. However, running validation has a performance cost. In
production, when the reliability of the data of a system is already established, and
they are expected to have complex DTDs and XML Schemas, the validating can
be turned off. Some parsers are non-validating by default.
Parsers can be of two types: tree-based parsing or event-based parsing. These
will be further discussed in Chapter 3, however, here is an overview:
Tree-based parsing
In tree-based parsing, the parsers attempts to create an hierarchal structure for
the entire document. For a hugh document, this will be extremely
memory-sensitive. The parser will make the elements and attributes available
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only after it has parsed the whole document. However, once the document has
been created in memory, it can be navigated and changed. A DOM parser would
be a tree-based parser.
Event-based parsing
These parsers process the document as it encounters the tags of the document.
It is a data-centric view of the XML. Whenever an element or tag is encountered,
it (or its contents) can be processed. However, it cannot backtrack once the tag
has been passed. The parser returns the element, its attributes and the contents.
The event-based parser never attempts to build a structure of the data, and
therefore, its memory requirements are less. It comes in useful, when one is
looking in the document only for certain elements. A SAX parser would be an
example of a event-based parser.
The most popular XML parsers on the market is the Apache XML Project’s
Xerces. The parsers provides XML parsing and generation, and are
fully-validating parsers available for both Java and C++, implementing the W3C
XML and DOM (Level 1 and 2) standards, as well as SAX (Level 2) standard. The
parsers also support for XML Schema. This parser has been incorporated into
the IBM set of products (WebSphere, Application Studio and DB2).
Another parser is IBM’s XML Parser for Java (XML4J and XML4C). The XML4J is
a validating XML parser written in 100% pure Java, whereas XML4C is a
validating XML parser written for C++. It provides classes for parsing, generating,
manipulating, and validating XML documents. Both parsers are support the XML
1.0 Recommendation and associated standards (DOM 1.0, SAX 1.0, DOM 2.0).
XML4J contains implementations of the DOM Level 2, the SAX Level 2
implementations, and parts of W3C schema, but these are experimental at this
stage. XML4C is supported on most operating systems including AIX and Linux.
Both parsers are open source and have the same code base, where the XML4J
parser has the latest code enhancements, while Xerces has been through
production level testing.
2.2 DTD and XML Schema
DTDs and XML Schema are both used to describe structured information,
however, in the last two years acceptance of XML Schema has gained
momentum. Both DTDs and schemas are building blocks for XML documents
and consists of elements, tags, attributes, and entities
XML Schemas evolved to overcome limitations in DTDs. W3C has three
documents published, the latest update being in May 2001:
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XML Schema Part 0: This is a primer, it is intended to provide an easily
readable description of the XML Schema facilities, and is oriented towards
quickly understanding how to create schemas using the XML Schema
language.
XML Schema Part 1: Structures specify the XML Schema definition language,
which offers facilities for describing the structure and constraining the
contents of XML 1.0 documents, including those which exploit the XML
Namespace facility.
XML Schema Part 2: Datatypes 2: It defines facilities for defining datatypes to
be used in XML Schemas as well as other XML specifications.
DTDs consists of elements that text string, text string with other child elements
and a set of child elements. DTDs also offer limited support for types and
namespaces. Lastly, the syntax in DTDs is not XML.
XML Schema is more powerful than DTD. Advantages of XML Schema over
DTDs are:
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Defines data types for elements and attributes, and their default and fixed
values. Some of the data types can be of string, decimal, integer, boolean,
date, time or duration. Altogether there are 19 built-in primitive data types and
23 built-in derived data types. Primitive data types are not defined in terms of
any other data types, whereas derived data types are defined in terms of
other data types.
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Apply restrictions to elements, by stating minimum and maximum values, (for
example, on age from 1 to 90 years), or restrictions of certain values (eg.
redbooks, residencies, Redpieces with no other values accepted, such as in a
drop-down list box). Restrictions can also be applied to types of characters
and their patterns (eg. only accepting values ‘a’ to ‘z’ and also specifying that
only three letters can be accepted). The length of the data can also be
specified. (Eg. passwords must be between 4 and 8 characters.)
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Specify complex element type. Complex types may contain simple elements
and other complex types. Restrictions can be applied to the sequence and
their frequency of their occurrences. These complex types can then be used
in other complex type elements.
Since schemas are written in XML, they are also extensible. The also implies
that the learning curve for learning another language has been eliminated, the
available parsers need not be enhanced, transformation can be carried out
using XSLT, and also its manipulation can be carried out using XML DOM.
With XML Schemas being extensible, they can be re-used in other schemas,
we can reference multiple schemas from the same document, and also have
the ability to create our own data types from standard data types.
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2.3 Schema and style using CSS, XSLT, and XSL
The eXtensible Style Language (XSL) is a language defined by the W3C for
expressing stylesheets. It has three parts:
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XSL Transformations (XSLT), which is used for transforming XML documents.
the XML Path Language (XPath), which is a language used to access or refer
to parts of an XML document.
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XSL-FO, which is a vocabulary for specifying formatting semantics.
A transformation in XSLT must be well-formed document and must conform to
the namespaces in XML, which can contain elements that may or may not be
defined by XSLT. XSLT-defined elements belong to a specific XML namespace. A
transformation in XSLT is called a stylesheet.
XSL uses a XML notation and works on two principles: pattern matching and
templates. It operates on an XML source document and parses it into a source
tree, it specifies the tansformation of the source tree to a result tree, and then it
outputs the result tree to a specified format. In constructing the result tree, the
elements can be reordered or filtered and also other structures can be added.
The result tree can be completely different from the source tree.
A stylesheet contains a set of template rules. A rule consists of two parts. The
first is a pattern that matches against nodes in the source tree, and the second is
a template, which is instantiated to form part of the tree. Therefore, documents
that have similar source tree structures can use one stylesheet.
The result tree is constructed by finding the template rule for the root node and
instantiating its template. This creates part of the tree. The template, in turn, can
contain elements from XSLT namespaces that are instructions for creating parts
of the tree. Each instruction in the template is carried out and that instruction
would result in a part of the tree being created. When the transformer is looking
for a applicable template rule, it may find more than one that matches it for an
element. Since only one rule can be applied, conflict resolution rules will be
applied. The rules are a combination of import precedence and priority. If the
transformer cannot resolve the conflict, it will signal an error.
XSLT makes use of the expressing language defined by XPath for deciding
elements for processing and generating text.
XSL transformation can be carried out either on a client or a server. On the client
side, Javascript could be used to determine the browser type of any operating
system characteristics and then applying different style sheets according to
browser and user needs. Obviously, the browser must support an XML parser.
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To make the XML data available to all kinds of browsers, we could transform the
XML document on the server and send it as a more generic form of HTML to the
browser. XSL transformations on the server will experience major growth as the
specialized browser market expands. The would include browsers for Braille,
aural browsers, Web printers, handheld devices and other kinds.
The W3C has published a working draft for a new set of requirements for XPath
on February 2001. It has set of number of goals. It has stated that XML must:
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Simplify manipulation of XML Schema-types content
Simplify manipulation of string-content
Support related XML standards
Improve ease of use
Improve interoperability
Improve i18n (International Language Support)
Maintain backward compatibility
Enable improved processor efficiency
For more information, visit W3C XSL Transformation (XSLT) Version 1 at:
W3C Xpath requirements Version 2.0 at:
Cascading Style Sheet (CSS)
Cascading Style Sheets were designed to help separate presentation from data
with HTML. In the early days, Netscape and Microsoft continued to customize
their browsers, by adding new tags, to add functionality to the HTML. For
developers, it became difficult to create Web sites where the content of the HTML
pages was clearly separated from the presentation layout. To alleviate this
problem, the W3C created Style Sheets. Style Sheets are usually saved in files
external to HTML.
CSS allows the Web developer to define styles that apply:
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To any given type of element (for example, all paragraphs)
To a class of elements (for example, all paragraphs which contain code
samples)
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To a particular element (for example, the third paragraph)
This is achieved by specifying classes and IDs in the HTML, and applying styles
to them.
The benefits of CSS are well-understood: Web developers can easily change the
layout and presentation of a whole site by editing a single stylesheet. CSS can be
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used with XML if the display engine supports it. So far, the only shipping browser
that supports this feature is Microsoft Internet Explorer 5.0.
CSS can be used within a document, or referenced in a separate stylesheet,
which is the more common approach. For more information on CSS, see:
The Cascading Style Sheet, Level 1 (CSS1) was made a full recommendation in
1996, while Cascading Style Sheet, Level 2 (CSS2) was made a full
recommendatory in 1998. CSS2 built upon CSS1, but had made no major
changes.
It can be said that CSS1 was a simple specification. It has a few limitations: It did
not say anything about tables on a HTML page. CSS2 did try to rectify this, by
introducing a new set of properties and behaviors, but these have not been
supported.
CSS1 does not incorporate absolute positioning within a table. It is possible to
define position relatively. The specification for CSS2 has devoted a number of
chapters for visual rendering, which includes the positioning of elements.
W3C has also published a working draft on CSS3 on its Web site in May 2001.
The main aim was to modularized the CSS specification. It is intended to clarify
the relationships between the different parts of the specification, and to reduce its
size.
2.4 XML namespaces
Namespaces are used when there is a need for elements and attributes of the
same name to take on a different meaning depending on the context in which
they are used.
For instance, a tag called <TITLE> takes on a different meaning, depending on
whether it is applied to a person or a book. If both entities (a person and a book)
need to be defined in the same document, for example, in a library entry which
associates a book with its author, we need some mechanism to distinguish
between the two and apply the correct semantic description to the <TITLE> tag
whenever it is used in the document. Namespaces provide the mechanism that
allows us to write XML documents which contain information relevant to many
software modules. Consider this example:
Example 2-1 A namespace example
<?xml version”1.0”?>
<library-entry xmlns:authr=”authors.dtd” xmlns:bk=”books.dtd”>
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<bk:book>
<bk:title>XML Sample</bk:title>
<bk:pages>210</bk:pages>
<bk:isbn>1-868640-34-2</bk:isbn>
<authr:author>
<authr:firstname>John</authr:firstname>
<authr:lastname>Smith</authr:lastname>
<authr:title>Mr</authr:title>
</authr:author>
</bk:book>
</library-entry>
In the example above, the <TITLE> tag is used twice, but in a different context,
once within the <AUTHOR> element and once within the <BOOK> element. Note
the use of the xmlns keyword in the namespace declaration. The XML
recommendation does not specify whether a namespace declaration should
point to a valid URI (Uniform Resource Identifier), only that it should be unique
and persistent. There is not guarantee that the URI will point to a valid URI.
In the example, in order to illustrate the relationship of each element to a given
namespace, we chose to specify the relevant namespace prefix before each
element. However, it is assumed that once a prefix is applied to an element
name, it applies to all descendants of that element unless it is over-ridden by
another prefix. The extent to which a namespace prefix applies to elements in a
document is defined as the namespace scope. If we were to use scoping, the
above example would then look like this.
Example 2-2 A namespace example using namespace prefix
<?xml version”1.0”?>
<library-entry xmlns:authr=”authors.dtd” xmlns:bk=”books.dtd”>
<bk:book>
<title>XML & WebSphere</title>
<pages>210</pages>
<isbn>1-868640-34-2</isbn>
<authr:author>
<firstname>Joe</firstname>
<lastname>Bloggs</lastname>
<title>Mr</title>
</authr:author>
</bk:book>
</library-entry>
In this example, it is clear that all elements within the <BOOK> element are
associated with the bk namespace, except for the elements within the
<AUTHOR> element which belong to the authr namespace.
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XML namespaces are used extensively in the XML arena, but, during the last two
years, there has not been much technological advancement in this area.
2.5 Link and jump using XLink, XPointer, and XML Base
Anyone surfing the Internet knows the joys of moving from one document to
another seemlessly. Links are easily embedded within one document to a
pre-defined location another. As demands for linking functionality, more demands
are required on the technology for more capabilities.
XLink, formerly known as XLL (the eXtensible Linking Language) provide
advanced linking capabilities, while XPointer provides ways describing locations
in XML documents. Xpointer is another layer built above XPath and is used to
locating data and ranges of data. XBase complements XLink and XPointer by
allowing developers to specify a document’s base URI. These can use the URI
do point to documents using relative parts.
XML documents should have the capability of being easily linked to one another,
and these links should be bi-directional. The basic unidirectional link is not
enough for future needs. The W3C published a XML Linking Language Version 1
recommendation in June 2001.
In the future, we would need some, if not all of the following capabilities:
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Multi-directional links: In today’s technology, we only have unidirectional links.
The only way to return to the location of the called document is to select the
Go Back button. With a multi-directional link, users could return to the original
location through a link at the first link’s destination.
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Link with multiple locations: There should be choice for different locations or
documents from a single link.
Placing content inline from a linked document: Presently, we cannot present
portions of two documents that are interlinked with one another.
The Xlink framework provides for a complex linking structures as will as
unidirectional links. Besides specifying the relationships of the two resources to
be linked, it can also associate meta data for that link.
The XLink type attribute may have one of the following attributes:
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Title: A description for another linking element
Simple: A simple link
Extended: A multi-resource link. An extended attribute can have locator, arc,
resource, and title as its child element types.
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Locator: Pointer to a external source. A locator can have a title as its child
element type.
Arc: A rule between resources. An arc element can have a title as its child
element type.
The simple and extended attributes are considered as linking elements. The other
attributes describe the link. A resource is any available information or service that
can be located by one means or another. The links, therefore, can link any two
resources: files, documents, images, query results, and programs. A resource
can refer to a portion of a resource, and may not have to refer to the whole file or
document. A local resource is specified by value and a remote resource is
specified by reference.
A transversal is a path from one resource to another. An arc describes the
traversal and application behavior between two resources. A link is
multi-directional if is coded such that the resources switch places at the starting
and ending resources. This is not the same as going back on the link. An arc is
out-bound if the starting resources is local and the ending resource is remote. An
example would be the HTML A element. Conversely, if the ending resource is
local, but the starting resource was remote, the arc is said to be in-bound. A
remote resource is one, which we do not have write access to or one we cannot
embed linking constructs.
remote. Typically, at any one time, the arc is in-bound, out-bound, or third-party.
Files or documents that contain a collection of in-bound and third-party links are
called linkups or link databases.
An example of a simple link is found in Example 2-3.
Example 2-3 A simple link
<passengers:FlightReference
xlink:href="passengerList.xml"
xlink:role="http://www.airline.com/linkproperties/passengerlist"
xlink:title="Passenger List">
xlink:show="replace"
xlink:actuate="onRequest">
List of Students for the Flight
</passengers:FlightReference>
A simple link in its simplest form provides an outbound link for two resources.
This would be very similar to the HTML-style A and IMG links. A click (for the
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example shown) on the simple link will open the resource pointed to in an
existing window.
An example of an XML document showing extended links is in Example 2-4.
Example 2-4 An extended link
<PassengerList>
<passengers
xlink:href="passengers/passengersConfirmed.xml"
xlink:label="passengersConfirmed020627"
xlink:role="http://www.airline.com/linkproperties/passConfirmed"
xlink:title="Confirmed Passengers" />
<passengers
xlink:href="passengers/passengersStandBy.xml"
xlink:label="passengersStandBy020627"
xlink:role="http://www.airline.com/linkproperties/passStandBy"
xlink:title="Stand By Passengers" />
<!-- more remote resources for Passengers, etc. -->
<flight
xlink:href="flight/united/Sydney020627.xml"
xlink:label="UA 0862"
xlink:title="United Airlines Ua 0862" />
<!-- more remote resources for courses, seminars, etc. -->
<go
xlink:from="UA 0862"
xlink:arcrole="http://www.airline.com/linkproperties/confirmed"
xlink:to="passengersConfirmed020627"
xlink:show="new"
xlink:actuate="onRequest"
xlink:title="Economy Class Confirmed Passengers" />
<go
xlink:from="UA 0862"
xlink:arcrole="http://www.airline.com/linkproperties/standby"
xlink:to="passengersStandBy020627"
xlink:show="replace"
xlink:actuate="onRequest"
xlink:title="Economy Class Stand By Passengers" />
</PassengerList>
When the entended link has a number of arcs, the specification does not say how
the target documents are to be treated. One option would have a pop-up menu
that lists all links and the resources found.
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For more details, visit W3C XML Linking language (XLink) V1.0 at:
XML Base
XML Base allows developers to specify a document’s base URI. Other links
within the same document can then specify links relative to this base. These links
could then point to applets, style sheets, images and other files. The syntax for
XML Base consists of a single XML attribute named xml:base.
A simple example follows for xml:base in a document with Xlink follows.
Example 2-5 An example of extended links using xbase
<?xml version="1.0"?>
<doc xml:base="http://airlines.org/tomorrow/"
xmlns:xlink="http://www.w3.org/1999/xlink">
<head>
<title>Passenger List</title>
</head>
<body>
<paragraph>Pick <link xlink:type="simple" xlink:href="passengers.xml">your
meal for the flights</link>!!!</paragraph>
<paragraph>Pick your meals for your flight tomoorw !</paragraph>
<meallist xml:base="/mealchoices/">
<item>
<link xlink:type="simple" xlink:href="choice1.xml">Choice 1: Beef
Vindalooo</link>
</item>
<item>
<link xlink:type="simple" xlink:href="choice22.xml">Choice 2: Chicken
Laksa</link>
</item>
<item>
<link xlink:type="simple" xlink:href="choice3.xml">Choice 3: United
Airlines Burger</link>
</item>
</meallist>
</body>
</doc>
The URIs resolving to full URIs would be:
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“Your meal for the flights” resolves to the URI
"http://airlines.org/tomorrow/passengers.xml"
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ꢀ
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“Choice 1: Beef Vindalooo" resolves to the URI
"http://airlines.org/mealchoices/choice1.xml"
“Choice 2: Chicken Laksa" resolves to the URI
"http://airlines.org/mealchoices/choice2.xml"
"Choice 3: United Airlines Burger" resolves to the URI
"http://airlines.org/mealchoices/choice2.xml"
As in XML, only Unicode characters are allowed in xml:base. But for the URI,
non-ASCII characters, except for the hash, percentage and square brackets, are
disallowed. All disallowed characters can be used provided they are converted to
UTF-8 or hexadecimal notation of the byte value, or if the character is replaced
by the character sequence.
The URI is resolved in the following priority:
1. The URI entry specified in the document
2. The URI of the encapsulating entity
3. The base URI is the URI used to retrieve the entity, or is defined by the
application.
The base URI may consists three parts in this order:
a. The base URI dictated by the xml:base attribute
b. The base URI of the element’s parent
c. The base URI of the document entity containing the element
It is best to provide an xml:base attribute as close to where the relative paths are
specified. If not, the xml:base attribute of the parent document comes into affect.
If the parent document is not available, then there might by difficult to determine
the absolute URI. For best results, the xml:base value should be provided either
directly or via default attributes declared in the internal subset of the DTD. Visit
W3C Web page to read more:
XML Pointer
The XML Pointer specification is the final part of the XLink specification. Where
XLink governs how you can insert links into your XML document and where the
link can point to anything, XPointer allows the user to point to specific part of the
document or a range, or area of the document. The user can then link the
address from one point of the document to another point in the same document.
IN HTML, using the ‘A’ and ‘IMG’ allows you to point from one document to
another, and only to a pre-determined spot. In an XML document, given its tree
structure, you should be able to navigate down to a child element or to a part of a
tree or from one part of a tree to another part of the tree.
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The XML Pointer Language (XPointer), the language defined to express
fragment identifiers for any URI reference that locates a resource whose Internet
media type is one of text/xml, application/xml, text/xml-external-parsed-entity, or
application/xml-external-parsed-entity.
Some examples of Xpointers follow. Each of these selects a particular element in
a document.
The example finds the element with the ID United:
http://www.airlines.com/airline.xml#xpointer(id("United"))
The example finds the second language element in the document:
http://www.airlines.com/airline.xml#xpointer(descendant::language[position()=2]
)
The third example is a shorthand form of finding the element with the ID United.
http://www.airlines.com/airline.xml#United
The next two examples are more involved. It shows how one navigates down a,
say a DOM tree. Here is shows the navigation from the root node, to the ‘spec’
child, and from it to all the second language elements from any of the child
elements:
http://www.airlines.com/airline.xml#xpointer(/child::spec/child::body/child::*/
child::language[2])
http://www.airlines.com/airline.xml#xpointer(/spec/body/*/language[2])
The last example finds the second child element of the fourteenth child element
of the root element:
http://www.airlines.com/airline.xml#/1/14/2
The final URI also points to the element with the ID United. However, if no such
element is present, it then finds the element with the ID UNITED:
http://www.airlines.com/airline.xml#xpointer(id("United"))xpointer(id("UNITED")
)
XPointer paths and steps
A XPointer path is made up from a number of steps. From a context node, each
step will relatively locate a specific point in the document. A location step has
three points: axis, node test and an optional predicate. This is in the form:
axis::node-test[predicate]
For aircraft::ROW[position()=34]:
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The axis is aircraft
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ꢀ
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The node test is ROW
The predicate is [position()=34]
This example located the 34th ROW element along from the content node.
The user can also specify the absolute location steps that do not depend on the
context node.
The location path of the XPointer is:
/child::BOEING747/child::ROW[position()=3].
This path is built from two location steps:
/child::BOEING747 and child::ROW[position()>34]
The first step is an absolute step that selects all child elements of the root node
whose name is BOEING747. This should return to exactly one such element.
The second step is then applied relative to the BOEING747 element returned by
the first step. All of its child nodes are considered. Those that satisfy the node
test, that is, elements whose name is ROW are returned. There might be 50
nodes. Therefore, all nodes from 35 to 50 are returned.
XPointer range functions
A range describes a contiguous part of a document. Location paths are identified
by location paths. To specify a range, the user appends /range-to(end-point) to
a location path specifying the start point of the range. An example would be:
xpointer(/child::BOEING747/child::ROW[position()=22]/range-to(/child::BOEING747
/child::ROW[position()=last()]))
Other range functions are:
range(location-set):Returns a set containing one range for each location
specified the argument. It is the minimum range necessary to cover the entire
location. In essence, it converts locations to ranges.
range-inside(location-set):Returns a set of locations inside the element with
the start and end tags not included. If the input location is a range or point, than it
points to that range or point.
start-point(location-set):Returns a set that contains the first point of each
location in the input location set. For example, start-point(//ROW[1]) returns
the point immediately after the first <ROW> start tag in the document.
start-point(//ROW) returns the set of points immediately after each <ROW> start
tag.
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end-point(location-set) - acts the same as start-point() but returns the points
just after each location in its input.
XPointer string functions
There are some basic string matching capabilities through this function:
string-range()- It takes a location set to search and a substring to search for.
The result is a location set having a single range. The index and length
arguments specify the number of characters where the match should start from
and the number of characters it should search for. Strings to be searched for are
case sensitive. Markup characters are ignored.
The basic syntax is:
string-range(location-set, substring, index, length)
The first argument is a location from which the document to be searched for the
matching string. The second argument is the actual string to search for. The
index argument must be a positive number to start after the beginning of the
match. The length argument can specify how many characters to include in the
range. If the last two arguments are not specified, then all characters are
assumed to require processing.
This example finds all occurrences of the string Boeing767:
xpointer(string-range(/,"Boeing767"))
The first argument can specify what nodes you want to look in. For example, this
finds all occurrences of the string Boeing767 in the UNITEDelements:
xpointer(string-range(//UNITED,"Boeing767"))
This example finds only the first occurrence of the string Boeing737 in the
document:
xpointer(string-range(/,"Boeing737")[position()=1])
This final position is immediately before the word Boeing737 in the document’s
UNITED element. This is not the same as pointing at the entire UNITEDelement as
an element-based selector would do.
A third argument, which is numeric, targets a particular position within the string.
This example targets the point between the l and ‘g’ in the first occurrence of the
string Boeing737 because ‘g’ is the sixth letter:
xpointer(string-range(/,"Boeing737",6)[position()=1])
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The optional fourth argument specifies the number of characters to select. The
example below, selects the ‘737’ from the first occurrence of the entire string
Boeing737:
xpointer(string-range(/,"Boeing737",7,3)[position()=1])
If the first string argument in the node test is empty, then relevant positions in the
context node's text contents are selected. In the example below, the first six
characters are picked up:
xpointer(string-range(/,""1,6)[position()=1])
See Related Publications.
2.6 XPath
XPath is to address parts of an XML document. Xpath supports XML
namespaces because XPath models an XML document as a tree of nodes (root
nodes, element nodes, attribute nodes, text nodes, namespace nodes,
processing instruction nodes, and comment nodes). The basic syntactic
construct in XPath is the expression. An object is obtained by evaluating an
expression, which has one of the following four basic types:
ꢀ
ꢀ
ꢀ
ꢀ
Node-set (an unordered collection of nodes without duplicates)
Boolean
Number
String
XPath uses path notation to define locations within a document. The paths
starting with a “/” signifies an absolute path. A simple example of this is shown
below.
Let us consider an XML document (Library.xml) which describes a Library
System. This sample document will be used throughout XPath and XPointer for
examples.
Example 2-6 An XPath example
<? xml version=”1.0”?>
<!DOCTYPE LIBRARY SYSTEM “library.dtd”>
<LIBRARY>
<BOOK ID=”B1.1”>
<TITLE>xml</TITLE>
<COPIES>5</COPIES>
</BOOK>
<BOOK ID=”B2.1”>
<TITLE>WebSphere</TITLE>
<COPIES>10</COPIES>
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</BOOK>
<BOOK ID=”B3.2”>
<TITLE>great novel</TITLE>
<COPIES>10</COPIES>
</BOOK>
<BOOK ID=”B5.5”>
<TITLE>good story</TITLE>
<COPIES>10</COPIES>
</BOOK>
</LIBRARY>
The path /child::book/child::copies selects all copieselement children of book,
which are defined under the document’s root. The above path can also be written
as /book/copies.
The XPath location step makes the selection of document part based on the
basis and the predicate. The basis performs a selection based on axis name and
node test. Then the predicate performs additional selections based on the
outcome of the selection from the basis. A simple example of this is as follows:
The path /child::book[position()-1] selects the first book element under root. This
location step can also be written as /book[1]
For example, the path /book/author/@* would have selected all the authorelements’
attributes
The path /book/author[@type=’old’] would have selected all the author elements
with type attribute equal to “old”.
The W3C has published a working draft for a new set of requirements for XPath
on February 2001. It has set of number of goals. It has stated that XML must:
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Simplify manipulation of XML Schema-types content
Simplify manipulation of string-content
Support related XML standards
Improve ease of use
Improve interoperability
Improve i18n (International Language Support)
Maintain backward compatibility
Enable improved processor efficiency
2.7 XML digital
Any document, XML or otherwise, can be encrypted entirely and be transmitted
to one or more recipients. Suppose we would only want to encrypt parts of the
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document of the same document. Also, we would like only different classes of
users to have access to different parts of the document. A airline agent may need
to know a passenger’s customer name and address, but does not need to know
the details of their credit card. A passenger boarding officer does not need to
have access to the passenger’s personal details, while the airline would want to
know more information about the passenger for marketing purposes.
It is fairly easy to encrypt a whole document, however, difficulty arises when
parts of a document needs to be signed by different people, and when this is to
be done with selective encryption.
One of the strengths of XML languages is that searching is clear and
unambiguous: The DTD or schema provides information syntax of the XML
document. If a document subsection including tags is encrypted as a whole, then
we are unable to search for data relevant for those tags. Also, the tags may
sometimes need to be hidden, and if they are known, could compromise security.
When sending secure data across the Internet, we need four things:
ꢀ
ꢀ
Confidentially: No one else can access or copy the data.
Integrity: The data is not altered as it gets transmitted from the sender to the
receiver.
ꢀ
ꢀ
Authentication: The document actually came from the purported sender.
Nonrepudiability: The sender cannot deny that they sent it, and the sender
also cannot deny the contents of the data.
The first three functions are provided for the Secure Sockets Layer (SSL). The
last function is provided for by the XML Security Suite.
The XML Security Suite provides several important functions:
ꢀ
XML Signatures: This implementation is based on the XML-Signature Core
Syntax and Processing specification being developed by W3C and the
Internet Engineering Task Force (IETF).
ꢀ
ꢀ
An implementation of the W3C's Canonical XML working draft
Element-level encryption
The XML signature and XML encryption are two initiatives designed to both
account for and take advantage of the special nature of XML data. These
initiatives are currently progressing through the standardization process. The
XML Signature initiative is a joint effort between the World Wide Web Consortium
(W3C) and Internet Engineering Task Force (IETF), and XML Encryption is solely
W3C effort.
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Examples of XML encryption
The main elements in the XML encryption syntax are the EncryptedData
element and the EncryptedKeyelement, which derive from the EncryptedType
abstract type. The data to be encrypted can be of an type, being an XML
document, element or element content. The result of encrypting data is an XML
encryption element that contains or references the cipher data. When an element
or element content is encrypted, the EncryptedData element replaces the
element or content in the encrypted version of the XML document.
When the data is encrypted, the EncryptedDataelement may become the root,
then the EncryptedData element may become the root of a new document.
However, the EncryptedData cannot be the parent or child of another
EncryptedData element, but the actual data encrypted can be anything including
existing EncryptedData or EncryptedKey elements.
A simple example follows in Example 2-7.
Example 2-7 Information on passenger John Smith
<?xml version='1.0'?>
<Credit Info xmlns='http://creditOrg.org/bills'>
<Name>John Smith<Name/>
<CreditCard Limit='21,000' Currency='AUD'>
<Credit Card Number>3760 098675 3245</Credit Card Number>
<Issuer>Wells Rago</Issuer>
<Expiry date>05/06</Expiry date>
</CreditCard>
</CreaditInfo>
Here we have selectively encrypted John Smith’s credit card details. The
EncryptedData elements now takes the place of the credit card element.
Example 2-8 Encrypted Information on passenger John Smith
<?xml version='1.0'?>
<CreditInfo xmlns='http://creditOrg.org/bills'>
<Name>John Smith<Name/>
<EncryptedData Type=’http://www.w3.org/2001/04/xmlenc#Element'
xmlns=’http://www.w3.org/2001/04/xmlenc#’>
<CipherData>
<CipherValue>W78G12I67</CipherValue>
</CipherData>
</EncryptedData>
</CreditInfo>
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In other cases, other information might be encrypted. Here are some of the credit
card details that have been left un-encrypted. This could happen if the credit limit
and the currency of the user’s details must be left visible to other parties.
Example 2-9 Encrypting only the credit card number
<?xml version='1.0'?>
<CreditInfo xmlns='http://creditOrg.org/bills'>
<Name>John Smith<Name/>
<CreditCard Limit='21,000' Currency='AUD'>
<Number>
<EncryptedData xmlns='http://www.w3.org/2001/04/xmlenc#'
Type='http://www.w3.org/2001/04/xmlenc#Content'>
<CipherData>
<CipherValue>P45K98W67</CipherValue>
</CipherData>
</EncryptedData>
</Number>
<Issuer>Wells Fargo</Issuer>
<Expiry date>05/06</Expiry date>
</CreditCard>
</CreditInfo>
Sometimes, it would be appropriate the encrypt the whole document.
Example 2-10 Encryption of the whole document
<?xml version='1.0'?>
<EncryptedData xmlns='http://www.w3.org/2001/04/xmlenc#'
Type='http://www.airline.com/flights/data/media-types/text/xml'>
<CipherData>
<CipherValue>I89H56V34</CipherValue>
</CipherData>
</EncryptedData>
The CipherData element can either envelop or reference the raw encrypted data.
In the first case, that raw data is shown by the contents of the CipherValue
element, while in the second a CipherReferenceelement is used, and this
encloses a URI, which points to the location of the encrypted data.
Example of a XML digital signature
The information that is signed is within the SignedInfoelement. The algorithms
used in calculating the SignatureValueelement are referenced within the signed
section, but that element itself is in the SignatureMethodelement. The
SignatureMethod references an algorithm used to convert the canonicalized
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SignedInfo into the SignatureValue. It is a combination of a key-dependent
algorithm and a digest algorithm, here DSA and SHA-1. The KeyInfoelement
indicates the key used to validate the signature. This element is not mandatory.
Example 2-11 An XML digital signature
<Signature Id="UnitedSignature" xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
<CanonicalizationMethod
Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
<SignatureMethod
Algorithm="http://www.w3.org/2000/09/xmldsig#dsa-sha1"/>
<Reference URI="http://www.w3.org/TR/2000/REC-xhtml1-20000126/">
<Transforms>
<Transform
Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
</Transforms>
<DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
<DigestValue>kgqwequetuwetqwetteuqteuyyey</DigestValue>
</Reference>
</SignedInfo>
<SignatureValue>iu7e876werew776er</SignatureValue>
<KeyInfo>
<KeyValue>
<DSAKeyValue>
<p>...</p><Q>...</Q><G>...</G><Y>...</Y>
</DSAKeyValue>
</KeyValue>
</KeyInfo>
</Signature>
Transforms
When a document or parts of a document are decrypted, we say it is transformed
into a decrypted form. The user may need to encrypt parts of a document that
already has parts of it that have been encrypted by another user. This user may
not be able, or may not need to, decrypt those parts that he has no authority of
interest over. The W3C published a candidate recommendation on Decryption
Transform for XML Signature in March 2002 that addresses this situation.
In the following example, some data (as in line 11) has already been encrypted,
and the user needs to further encypted data of his own.
Example 2-12 Part encryption of an XML document
[01]<ticket Id="EXTYGH">
[02] <passengers>
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[03]
[04]
[05]
<name>Jenny Smith</name>
<cost>230.0</cost>
<seats>4</seats>
[06] </passengers>
[07] <cardcard>
[08]
[09]
[10]
<name>John Smith</name>
<expirydate>02/2006</expirydate>
<cardnumber>3760 234567 76547</cardnumber>
[11] </cardcard>
[12] <EncryptedData
Id="enc1"xmlns="http://www.w3.org/2001/04/xmlenc#">...</EncryptedData>
[13]</ticket>
After this user signs and encrypts this document, it would look like Example 2-13.
Example 2-13 The final XML document after encryption
[01] <Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
[02] <SignedInfo>
[03]
[04]
[05]
[06]
...
<Reference URI="#order">
<Transforms>
<Transform
Algorithm="http://www.w3.org/2001/04/xmlenc#decryption">
[07] <DataReference URI="#enc1"
xmlns="http://www.w3.org/2001/04/xmlenc#"/>
[08]
[09]
</Transform>
<Transform
Algorithm="http://www.w3.org/TR/2000/CR-xml-c14n-20001026"/>
[10]
[11]
[12]
</Transforms>
...
</Reference>
[13] </SignedInfo>
[14] <SignatureValue>...</SignatureValue>
[15] <Object>
[16]
[17]
[18]
[19]
[20]
[21]
[22]
<ticket Id="EXTYGH">
<passengers>
<name>Jenny Smith</name>
<cost>230.0</cost>
<seats>4</seats>
</passengers>
<EncryptedData Id="enc2" xmlns="http://www.w3.org/2001/04/xmlenc#">
...</EncryptedData>
[23]
[24]
<EncryptedData Id="enc1" xmlns="http://www.w3.org/2001/04/xmlenc#">
...</EncryptedData>
</ticket>
[25] </Object>
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[26] </Signature>
The signature element now encompasses the whole order, and the ticket
elements is now embedded within it (lines 16 to 24 ). We have now encrypted the
credit card details that were between lines 7 to 11 of the previous listing. The
Transform element on line 6 to 10, indicates that there are two transform
references. The first, decryption (in lines 6 to 8) and canonizations (in line 9). The
Decryption Transform, decrypts all the data, except for that on line 7, “enc1”, as
specified in the DataReference element. Once this decryption in the
EncryptedData element has taken place, the signature is verified. This signature
verification information is in the signature value element.
Other security specifications
XML security is still inadequate, and has some way to go before it will be fully
accepted. The other specifications that have been raised to address various
issues are:
ꢀ
ꢀ
ꢀ
SAML :Security Assertion Markup Language - "XML security standard for
exchanging authentication and authorization information."
XACML : eXtensible Access Control Markup Language - A language used for
define rules and access privileges for XML documents.
XKMS : W3C’s XML Key Management Specification published in March 2001.
This document specifies protocols for distributing and registering public keys
Visit following Web sites to read more details.
W3C Signature Work Group at:
W3C Decryption Transform for XML Signature at:
Enabling XML Security: An Introduction to XML encryption and XML Signature
by Murdoch Mactaggart at:
2.8 XML query language
In February 2001, W3C published a working draft for the XML query language. In
April 2002, another working draft was published. These papers had heavy IBM
involvement. When the publication is a working draft, it can be updated, replaced
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and made obsolete by other documents at any time. Because it contains many
open issues it is considered to be fully stable.
The first draft introduced the XQuery language and provided examples, while the
second draft introduced function signatures and other expressions. The second
draft exemplified the semantics of element and attributes, and how the
underlaying data was operated upon.
The XML query language was specified to be one that made use of XML
structure, and have the ability to, “conduct queries across all these kinds of data,
whether physically stored in XML or viewed as XML via middleware.”
This section of the book does not go into the details of XQuery, but provides
examples to show the main flow of the language. This will provide an overview of
what XQuery is likely to provide. The examples and explanations that follow are
taken from the first draft.
The XQuery language consists of the forms below. Explanations of some are
given:
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Path expressions
Element expressions
FLWR ( “FOR, LET, WHERE, and RETURN clauses”)
Expressions involving operators and functions
Conditional expressions
Quantified expressions
List constructors
Expressions that test and modify datatypes
Path expressions
A path expression is a series of steps, where one step of the path may serve as
an endpoint, or may have multiple values. Each step may serve as a starting
point of the next step, if they exist. Here are some queries expressed in the
English form, and then the XQuery form:
In the second chapter of the document named “zoo.xml”, find the figure(s) with
caption “Tree Frogs”.
document("zoo.xml")/chapter[2]//figure[caption = "Tree Frogs"]
In this example, the first step finds the document, the second locates Chapter 2,
and the last step filters all captions in that chapter for “Tree Frogs”.
Find all the figures in Chapters 2 to 5 of the document named "zoo.xml."
document("zoo.xml")/chapter[RANGE 2 TO 5]//figure
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This example demonstrates use of the RANGE predicate. The first element
always has a ordinal number of 1.
Find captions of figures that are referenced by <figref> elements in the chapter of
"zoo.xml" with title "Frogs".
document("zoo.xml")/chapter[title = "Frogs"] //figref/@refid->fig/caption
XQuery has allowed for a de-reference operator(“->”). In HTML, IDREF and
IDREFS values refer to values of other elements' ID attributes. An IDREF value is
a single ID while an IDREFS value is a space-separated list of IDs. IDREF and
IDREFS are case-sensitive. In this case, the deference operator follows the
IDREF-type attribute, and returns elements referenced by the attribute. In the
example above, the de-reference operator locates, in the “figref” element, in the
“refid” attribute, the caption of the “fig” element.
List the names of the second-level managers of all employees whose rating is
"Poor".
/emp[rating = "Poor"]/@mgr->emp/@mgr->emp/name
Here the query locates, where the employees having a “poor” rating, the name of
the employees by looking up another emp element having a “mgr” attribute.
In the document "zoo.xml", find <tiger> elements in the namespace defined by
www.abc.com/names that contain any supplement in the namespace defined by
www.xyz.com/names:
NAMESPACE abc = "www.abc.com/names"
NAMESPACE xyz = "www.xyz.com/names"
document("zoo.xml")//abc:tiger[xyz:*]
Here query provides syntax for URIs. A default namespace can also be specified
as in this last example:
NAMESPACE DEFAULT = "www.abc.com/names"
NAMESPACE xyz = "www.xyz.com/names"
document("zoo.xml")//tiger[xyz:*]
Element constructors
The typical use of an element constructor is that it is nested inside another
expression that binds one or more variables.
Generate an <emp> element containing an "empid" attribute and nested <name>
and <job> elements. The values of the attribute and nested elements are
specified by variables that are bound in other parts of the query:
<emp empid = $id>
<name> $n </name> ,
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<job> $j </job>
</emp>
Generate an element with a computed name, containing nested elements named
<description> and <price>:
<$tagname>
<description> $d </description> ,
<price> $p </price>
</$tagname>
In this example, the tagname, with its end-tag itself is a variable.
FLWR(“FOR, LET, WHERE and RETURN clauses”) expression
A FLWR expression binds values to and more variables, and then uses these
variables to construct a result. For the following example, the XML file would
follow the structure shown:
<book>
<title>...</title>
<author>.....</author>
<author>....</author>
<publisher>...</publisher>
<price>.......<price>
<year>....<year>
</book>
List the titles of books published by Morgan Kaufmann in 1998:
FOR $b IN document("bib.xml")//book
WHERE $b/publisher = "Morgan Kaufmann"
AND $b/year = "1998"
RETURN $b/title
List each publisher and the average price of its books:
FOR $p IN distinct(document("bib.xml")//publisher)
LET $a := avg(document("bib.xml")
/book[publisher = $p]/price)
RETURN
<publisher>
<name> $p/text() </name> ,
<avgprice> $a </avgprice>
</publisher>
Conditional expressions (IF THEN ELSE)
Conditional expressions are used when the information returned from a query
depends on some condition.
Make a list of holdings, ordered by title. For journals, include the editor; and for all
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other holdings, include the author:
FOR $h IN //holding
RETURN
<holding>
$h/title,
IF $h/@type = "Journal"
THEN $h/editor
ELSE $h/author
</holding> SORTBY (title)
Quantifiers
Sometimes we have to test if elements exist that must satisfy a condition.
Find titles of books in which both sailing and windsurfing are mentioned in the
same paragraph:
FOR $b IN //book
WHERE SOME $p IN $b//para SATISFIES
contains($p, "sailing")
AND contains($p, "windsurfing")
RETURN $b/title
Eg 12. Find titles of books in which sailing is mentioned in every
paragraph.
FOR $b IN //book
WHERE EVERY $p IN $b//para SATISFIES
contains($p, "sailing")
RETURN $b/title
Filtering
This filter function takes two operands, each of which is an expression that
evaluates to a ordered set of notes, and returns copies of some of the nodes in
the first operand, while preserving their hierarchic and sequential relationships.
The second operand is the filter that trims the hierarchical tree. Both operands
must have the same node, not only two nodes of the same value. If the two
operands do have a common root, the result of the filter function is an empty list.
The following example illustrates this process by computing a table of contents
for a document, which contains many levels of nested sections. The query filters
the document and retaining only section elements, title elements nested directly
inside section elements, and the text of those title elements. Other elements,
such as paragraphs and figure titles, are eliminated, leaving only the skeleton of
the document.
The first argument of filter is the root of a document, and the second argument is
a path expression that identifies the nodes to be preserved from the original
document.
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Prepare a table of contents for the document "cookbook.xml", containing nested
sections and their titles:
LET $b := document("cookbook.xml")
RETURN
<toc>
filter($b, $b//section | $b//section/title | $b//section/title/text() )
</toc>
Querying relational data
The best way to demonstrate XQuery is showing how it can be used to query a
relational database. In Table 2-1 we have a very simple database.
Table 2-1 Example schema for relational database and Xquery comparison
Table name
Relational data
XML representation
S
SNO
<s>
SNAME
<s_tuple>
<sno>
<sname>
P
PNO
<p>
DESCRIP
<p_tuple>
<pno>
<descrip>
SP
SNO
<sp>
PNO
PRICE
<sp_tuple>
<sno>
<pno>
<price>
SQL is the standard relational database language. In many cases, SQL queries
can be converted to XQuery syntax in a straightforward way by mapping SQL
query-blocks into FLWR-expressions. We illustrate this mapping by the following
query:
Find the part numbers of gears in numeric order:
SQL version:
SELECT pno
FROM p
WHERE descrip LIKE 'Gear'
ORDER BY pno;
XQuery version:
FOR $p IN document("p.xml")//p_tuple
WHERE contains($p/descrip, "Gear")
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RETURN $p/pno SORTBY(.)
Grouping in XQuery
Find the part number and average price for parts that have at least three
suppliers.
SQL version:
SELECT pno, avg(price) AS avgprice
FROM sp
GROUP BY pno
HAVING count(*) >= 3
ORDER BY pno;
XQuery version:
FOR $pn IN distinct(document("sp.xml")//pno)
LET $sp := document("sp.xml")//sp_tuple[pno = $pn]
WHERE count($sp) >= 3
RETURN
<well_supplied_item>
$pn,
<avgprice> avg($sp/price) </avgprice>
</well_supplied_item> SORTBY(pno)
The $pn represents an individual part number, but $sprepresents a set of
records.
Joins
Joins combine data from multiple sources. We will present a simple example with
an inner join.
Return a "flat" list of supplier names and their part descriptions, in alphabetic
order:
FOR $sp IN document("sp.xml")//sp_tuple,
$p IN document("p.xml")//p_tuple[pno = $sp/pno],
$s IN document("s.xml")//s_tuple[sno = $sp/sno]
RETURN
<sp_pair>
$s/sname ,
$p/descrip
</sp_pair> SORTBY (sname, descrip)
In conclusion, XQuery is designed to support many types of queries. The more
versatile the Xquery is, the more it will provide usability for XML for applications.
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For more detail, visit XQuery 1.0: An XML Query Language ( April 2002 ) at:
XQuery: A Query Language for XML (Feb 2002) at:
As the use of XML documents climbs, so will the use of XSL transformations
increase. For any project, this increase will not only be in terms of the number of
number of XSLT engines on the market today, but these are all interpreters
(Figure 2-1).
Transformations are generally static and can be used multiple times over different
XML documents. If these transformations could be pre-compiled, we would
realize performance levels in speed and for memory (Figure 2-2).
Java classes that offer translation capabilities are called translets. Translets can
offer significant speed in server-side transformations, and also the possibility of
client-side transformation of XML into other formats. Translets are expected to be
small, in the 100 Kilobytes range.
XSLT
stylesheet
<xsl:template match="Customer">
<h1>Input XML Form</h1>
<form action="/Travel/CustomerXSLServlet" method="post">
<table border="0" cellpadding="2" cellspacing="0">
<xsl:apply-templates select="firstname"/>
</table>
</form>
</xsl:template>
Output
XML,
HTML, etc
XML input
file
XSLT processor
Figure 2-1 XSLT interpreters
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<xsl:tem plate m atch="Custom er">
<h1>Input XML Form </h1>
<form action="/Travel/Custom erXSLServlet" method="post">
<table border="0" cellpadding="2" cellspacing="0">
<xsl:apply-tem plates select="firstnam e"/>
</table>
XSLT
stylesheet
</form >
</xsl:tem plate>
Compiler
JVM
transA.class
bytecode
Output
XM L,
HTM L, etc
XM L input
file
translet running
on JVM
Figure 2-2 The XSLT compiler
The Apache XML project ( xml.apache.org) provides XSLTC, which is a compiler
and runtime processor. The compiler can be used to compile an XSL stylesheet
into a set of Java classes called translets. The classes than can be deployed, just
like any other Java classes, along with the xsltc.jar and the runtime.jar. The
compiler and the translets can be run from the command line, and also the
TrAX/JAXP API. TrAX provides a framework and a standard API for performing
XML transformation, and it uses systems properties to locate the Transformer
and the XML parser.
The JAXP API can be found in the Java XML Pack, which can be downloaded
from the Sun Web site. Besides the two methods, the XSLTC can also be used
with the native Java API.
Xalan-Java Version 2 is an XSLT processor built upon on SAX 2 and DOM 2. It
implements the W3C recommendations for XSLT and the XMl Path language
(XPath). It can be used from the command line, in a Java class (applet or
servlet), or as a module in another program.
For more details, visit Using XSLTC:The Apache XML Project at:
Xalan-Java version 2.4.D1: The Apache XML project at:
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2.10 Java Architecture for XML Binding (JAXB)
The Java Architecture for XML Binding provides an API and tools that automate
the mapping between XML documents and Java objects. These are available as
an early access release. The public version of the JAXB specifications and a
pre-release version of the reference implementation will be available by the third
quarter 2002. The final draft is scheduled to be published in the forth quarter of
the same year.
The JAXB API compiles an XML Schema into Java classes. The Java classes
handle all the details of XML parsing and formatting. The generated classes
ensure that the constraints expressed in the DTD are enforced in the methods
and Java technology language data types. The early access release only works
on DTD, but later versions are being produced to support other schemes.
The classes generated by JAXB perform at a greater efficiency than the SAX and
DOM parsers, because the classes are more customized than the generic
parsers. The generated application validates structure and content with the help
of the Java classes. The structure and content validation classes perform better
than the SAX, because the derived classes are precompiled. Unlike the DOM
parser, it does not need to create the whole tree. The content tree created is
specific to one schema, and the classes do not need any redundant
tree-manipulation functionality.
The JAXB expert group is now working on the new specification. Among the
features are:
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ꢀ
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Support for a subset of W3C XML Schema and XML namespaces
More flexible unmarshalling and marshalling functionality
Enhanced validation capabilities, such as allowing validation to be turned on
for development purposes, and turned off for deployment.
To understand JAXB in depth, visit Java Architecture for XML Binding (JAXB) at
Java.sun.com:
2.11 Cocoon
Cocoon provides an XML publishing framework that is designed around the SAX
API. It can interact with common data sources, including files, relational
databases, and XML databases. The content delivery can be customized to
different devices such as HTML, WML, RTF, PDF and others. Its main aim is to
provide a platform for building applications with distinct separation between
content, logic, and presentation.
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49
The latest version is Cocoon 2 and is available for download from:
It is a Web based application and must be run upon a Java Servlet 2.2 compliant
engine, and also Jakarta Tomcat 4.0.1
In Cocoon, everything can be perceived as part of a pipeline. A pipeline consists
of an input, some processing steps and then an output. Cocoon 2 makes use of
the SAX events between each processing step. Parts of the pipeline include a
generator and a serializer. The generator is used for input, the serializer
produces output and the transformer is used for processing intermediate steps.
These components can be grouped together into several distinct types,
depending on the roles they play within a pipeline:
Generators and reader: pipeline inputs
Generators are used for inputing data source and passing it on as a series of
SAX events. The simplest generator is therefore a SAX parser. Generally, any
data source that can be mapped to a series of SAX events can become the basis
for a generator.
Transformers and actions: processing steps
The main processing steps in the pipeline are handled by the transformers
(Figure 2-3). They accept SAX events as input, perform a number of useful
processing steps, and then the results produced are passed down the pipeline as
SAX events. The most common transformer one can find is the XSLT
Transformer. Input is fed into an XSLT processor which performs an XSLT
transformation. The results of the transform are then fed back into the pipeline as
SAX events.
Serializer: pipeline outputs
Serializers render the output from a stream of SAX events produced from a
generator or a transformer. The format of the output is dependent on the
serializer specified. Serializers are the endpoints in Cocoon pipelines. The most
basic serializer is the XML serializer, which simply turns the SAX events back
into an XML document, while other serializer produce HTML, PDF documents,
and images to name a few. The serializers need to have the SAX events stream
to be of a particular XML vocabulary: A HTML Serializer turns XHTML into valid
HTML, a PNG images and PDF Serializer: Turns XSL-FO into a PDF document
and a SVG Serializer turns SVG into JPEG.
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Matchers and selectors: conditional processing
Conditional statements are part of any programming language. Output can be
dependent on many factors, such as the users’ browser, request parameters, or
operating system.
Matchers are the equivalent of If statements. If a condition is true, then a section
of a pipeline is processed, or otherwise is passed by.
A selector is used when there are few options available, and it is similar to an
If-then-else statement. These are used to create conditional sections in the
pipeline, while matchers are used to test if a particular pipeline is to be
processed.
SAX
SAX
File Generator
FileSerializer
FileTransformer
request
reponse
XSL StyleSheet
HTML, PDF, etc
HTML
Figure 2-3 Cocoon components
Sitemap
The Cocoon sitemap fulfills two functions:
ꢀ
ꢀ
Components (matchers, generators, serializers, transformers, etc.) are
declared here before being used in pipelines.
Where pipelines are declared using the declared components.
It consists of configuration data for the Cocoon engine.
Example 2-14 Sample sitemap for Cocoon
<map:match pattern=”airline.html””>
<map:generate src=”docs/flight_data.xml”/>
<map:transform src=stylesheets/page/airline.xsl”/>
<map:serialize type=”html”/>
</map:match>
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The sitemap is a XML file and is responsible for declaring individual components.
It is used to define how those components are used to construct pipelines.
Declaring components within the sitemap provides Cocoon with a great deal of
extensibility, allowing the plug-and-play addition of new implementations.
The sitemap XML file has the structure shown below:
Example 2-15 Components of a sitemap XML file
<map:sitemap xmlns:map="http://apache.org/cocoon/sitemap/1.0"> <map:components>
<!-- component declared here -->
<map:generators/>
<map:readers/>
<map:transformers/>
<map:actions/>
<map:serializers/>
<map:actions/>
<map:matchers/>
<map:selectors/>
</map:components>
<map:pipelines>
<!-- pipeline definitions declared here-->
</map:pipelines>
</map:sitemap>
It refers to a specific namespace: ‘"http://apache.org/cocoon/sitemap/1.0",
which is used to identify all the elements. As mentioned earlier, the file is divided
into two sections: map:components and map: pipelines, reflecting its
responsibilities.
This section of this chapter has only served as an introduction to Cocoon. Any
further discussions would have involved starting a new chapter. Like any other
emerging technology, it tries to compartmentalize data from logic and
presentation. Its further acceptance will depend on how much it can keep up with
the ever changing requirements of rapidly changing industry.
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Part 2
XML technology in
IBM WebSphere
This part introduces IBM WebSphere Studio family and introduces the XML
development capabilities of Websphere Studio Application Developer using XML
perspective and wizards.
© Copyright IBM Corp. 2002. All rights reserved.
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3
Processing XML
Chapter three provides the reader with an opportunity to learn about the
processing of XML documents. The chapter highlights the XML Processor and
parser shipped with WebSphere Application Developer.
In this chapter, the following topics are described:
ꢀ
ꢀ
ꢀ
ꢀ
Xalan XSLT Processor
SAX2
DOM Level2
Java API for XML Processing (JAXP)
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3.1 XML applications
Today’s organizations’ rapid movement towards e-business brings new demands
on defining flexible systems architectures. Systems need to be powerful,
scalable, robust, and most of all, capable of meeting new business requirements.
With that in mind, applications often need to be able to support multiple client
types, all with different capabilities. The dominant client type for Web applications
is currently the desktop browser, but that will not last forever. Pervasive
Computing is rapidly evolving, introducing the use of cellular phones, PDAs, and
other front-end devices, all with different XML capabilities. So as time passes by,
each application gets a much broader audience, using a variety of new devices
for sending and receiving information.
The most recent edition of any browser that might have XML support cannot be a
prerequisite for using an XML based application. We also do not want to send the
same XML document to every client, because some users of the application
might be authorized to see more data than others. We must have the ability to
process XML documents and generate the kind of response to the client that is
adequate for the client type.
Extensible Stylesheet Language Transformations (XSLT) is designed to
transform XML data into some other XML form. An XSLT processor, such as
Apache’s Xalan, performs transformations using one or more XSLT stylesheets,
which are also XML documents. Typically, in an XSLT- and Java-based Web
application, XML data is generated dynamically based on database queries.
Although some databases can export data directly as XML, you will often write
custom Java code to extract data using JDBC and convert it into XML. In order to
display this XML data on most browsers, it must first be converted into HTML.
The XML data is fed into the processor as one input, and as XSLT stylesheet is
provided as a second input. The output is then sent directly to the Web browser
as a stream of HTML. The XSLT stylesheet produces HTML formatting
instructions, while the XML provides raw data.
So in conclusion, at the heart of every XML application is an XML Processor that
parses an XML document, so that the document elements can be retrieved and
transformed into a presentation understood by the target client. The other
responsibility of the parser is to check the syntax and structure of the XML
document. The focus of this chapter is on the Xalan Java processor with all the
aspects involved in processing an XML document.
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3.2 Xalan
Xalan is an XSLT processor for transforming XML documents into HTML, text, or
other XML document types. It implements the W3C Recommendations for XSL
Transformations (XSLT) and the XML Path Language (XPath). It provides a
Level2, and the XML parser API in Java API for XML Parsing 1.0 (JAXP). It may
be configured to work with any XML parser, such as Xerces, that implements
JAXP. It can process Stream, SAX or DOM input, and output to a Stream, SAX or
DOM.
The diagram in Figure 3-1 shows a high level model of operation. A
transformation expressed in XSLT describes the rules for transforming a source
tree into a result tree. A term tree represents the structure of an XML document,
whether it is a DOM tree, or a series of parse events coming from a SAX2
ContentHandler. The transformation is achieved by associating patterns with
templates. A pattern is matched against elements in the source tree. A template
is instantiated to create part of the result tree. The result tree is separate from the
source tree. The structure of the result tree can be completely different from the
structure of the source tree. In constructing the result tree, elements from the
source tree can be filtered and reordered.
Source
XML
Result
XML
XSLT
Engine
XSL
Style
Sheet
Figure 3-1 Xalan model of operation
The primary interface for Xalan for external usage is javax.xml.transform. These
interfaces define a standard and powerful interface to perform tree-based
transformations. These interfaces have no dependencies on SAX or the DOM
standard as shown in Figure 3-2. It achieves this by defining source and result
interfaces, which a user can use to define instances of whatever input and output
desired, whether SAX, DOM, or stream.
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57
TransformerFactory
creates
Templates
(stylesheet)
invokes
input
output
Transformation
Result
Source
result specification
source specification
DOM
SAX
Source
SAX
Result
Result
Stream
Source
Stream
Result
DOM
Source
Figure 3-2 javax.xml.transforms interfaces operation
3.3 SAX2
SAX is the Simple API for XML, originally a Java-only API. SAX was the first
wisely adopted API for XML in Java. SAX APIs are event-based APIs, which
report parsing events (such as start and end elements) directly to the application
through callbacks, and does not usually build an internal tree. These event-driven
them. They cannot be used to manipulate the internal structures of XML
documents. As the XML document is parsed, the application using SAX receives
information about the various parsing events. The application implements
handlers to deal with these different events, much like handling events in a
graphical user interface. The logical structure of an application using SAX API
with the parser is shown in Figure 3-3. You can parse documents much larger
than your available system memory, and you can construct your own data
structures using your callback event handlers.
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X M L
A p p lic a tio n
S A X A P I
X M L P a r s e r
X M L
D o c u m e n t
Figure 3-3 SAX application components
To understand how an event-based API can work, consider the sample document
in Example 3-1.
Example 3-1 Sample XML document
<?xml version="1.0" encoding="UTF-8"?>
<Customer>
<name>Mary Smith</name>
<membership>10001</membership>
</Customer>
An event-based interface will break the structure of this document down into a
series of linear events, such as those shown in Example 3-2.
Example 3-2 Sample event breakdown
start document
start element: Customer
start element: name
characters: Mary Smith
end element: name
start element: membership
characters: 10001
end element: membership
end element: Customer
end document
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59
An application handles these events just as it would handle events from a
graphical user interface; there is no need to cache the entire document in
memory or secondary storage.
Currently, there are two versions of SAX: 1.0 and 2.0. Many changes were made
in version 2.0. The focus of this chapter is on SAX version 2.0. Most SAX parsers
should support the older 1.0 classes and interfaces, however, you will receive
deprecation warnings from the Java complier if you use these older features.
SAX2 classes and interfaces
The following interfaces and classes are provided by SAX2:
ꢀ
ꢀ
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ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
org.xml.sax.XMLReader which replaces SAX1 Parser
org.XML.sax.XMLFilter
org.xml.sax.ContentHandler which replaces SAX1 DocumentHandler
org.xml.sax.Attributes which replaces SAX1 AttributeList
org.xml.sax.SAXNotSupportedException
org.xml.sax.SAXNotRecognizedException
org.xml.sax.helpers.AttributesImpl which replaces SAX1 AttributeListImp
org.xml.sax.helpers.NamespaceSupport
org.xml.sax.helpers.XMLFilterImpl
org.xml.sax.helpers.ParserAdapter
org.xml.sax.helpers.XMLReaderAdapter
org.xml.sax.helpers.DefaultHandler which replaces SAX1 HandlerBase
SAX2 contains complete namespace support, which is available by default from
any XMLReader. AN XML reader can also optionally supply raw XML 1.0 names.
Have a look at “XML namespace support” on page 61 for more details about
SAX2 support for XML namespaces.
The ContentHandler and Attribute interfaces are similar to the deprecated
DocumentHandler and AttributeList interfaces, but they add support for the
namespace related information. ContentHandler also adds a callback for skipped
entities, and Attributes adds the ability to look up an attribute’s index by name.
The ContentHandler interface is regarded as the most important of the all, as it
has methods such as startDocument(), startElement(), characters(),
endElement(), and endDocument(). During the parsing process, startDocument()
is called once, then startElement() and endElement() are called once for each
tag in the XML data. The characters() method provides the text value of the
element. This process continues until the end of the document, at which time
endDocument() is called.
Since ContentHandler is an interface, it is up to your application code to
somehow implement this interface and subsequently do something when the
parser invokes its methods. SAX does provide a class called DefaultHandler that
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implements the ContentHandler interface. To use DefaultHandler, create a
subclass and override the methods that interest you. The other methods can
safely be ignored, since they are just empty methods.
The ParserAdapter class makes a SAX1 Parser behave as a SAX2 XMLReader.
The XMLReaderAdapter class makes a SAX2 XML reader behave as a SAX1
parser. The two classes should ease the transition from SAX1 to SAX2 by
allowing SAX1 drivers and clients to co-exist with SAX2 drivers and clients in the
same application.
XML namespace support
SAX2 adds XML namespace support. Every implementation of the SAX2
XMLReader interface is required to support namespace processing in its default
state. Additionally, many XML readers allow namespace processing to be
modified or disabled. Namespace processing changes only element and attribute
naming, although it places restrictions on some other names. Each XML element
and attribute has a single name called the qName which may contain colons.
With namespaces, elements and attributes have two-part name, sometimes
called the universal or expanded name, which consists of a URI, and a
localName.
SAX2 is capable of supporting either of these views or both simultaneously.
implementations are required to report the namespace style names when
documents use them.
Namespace support affects the ContentHandler and Attributes interfaces. In
SAX2, the startElementand endElementcallbacks in a content handler look like
Example 3-3 on page 61.
Example 3-3 SAX2 callback methods
public void startElement (String uri, String localName,String qName,
Attributes atts) throws SAXException;
public void endElement (String uri, String localName, String qName)
throws SAXException;
By default, an XML reader will report a namespace URI and a local name for
every element that belongs to a namespace, in both the start and end handler.
Consider Example 3-4 on page 61.
Example 3-4 Sample namespace
<html:hr xmlns:html="http://www.ibm.com"/>
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61
With the default SAX2 namespace processing, the XML reader would report a
start and end element event with the namespace URI http://www.ibm.com and
the local name hr. Most XMLReader implementations also report the original
qName html:hr, but that parameter might simply be an empty string (except for
elements that are not in the namespace).
For attributes, you can look up the value of a named attribute using the getValue
method, and you can look up the namespace URI or local name of an attribute by
its index using the getURIand getLocalNamemethods. If the URI were the empty
string, you would normally use the qName to identify the attributes.
In addition to those events, SAX2 reports the scope of namespace declarations
using the startPrefixMappingand endPrefixMapping methods, so that
applications can resolve prefixes in attribute values or character data if
necessary.
3.4 DOM level2
While XML is a language to describe tree-structures data, the Document Object
Model (DOM) defines a set of interfaces to access tree-structures XML
documents. DOM specifies how XML and HTML documents can be represented
as objects. Unlike SAX, DOM also allows creating and manipulating the contents
of XML documents.
DOM level2, contains interfaces for creating a document, importing a node from
one document to another, supporting XML Namespaces, associating stylesheets
with a document, the Cascading Style Sheets object model, the Range object
model, filters and iterators, and the Events object model. The DOM Core API
allows the creation and population of a Document object using only DOM API
calls; loading a Document and saving it persistently is left to the product that
implements the DOM API.
DOM hierarchy
The DOM provides a set of standard object interfaces that an XML parser can
use to expose the contents of a document to a client application. These
interfaces provide access to all the information from the original document,
organized in a hierarchical tree structure. The base interface for navigating this
tree structure is the Nodeinterface, that defines the necessary methods to
navigate and manipulate the tree-structure of XML documents. The methods
include getting, deleting, and modifying the children of a node, as well as
inserting new children to it. Every specific document structure is represented in
the DOM by one of the following specialized interfaces:
ꢀ
Document
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ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Attr
Element
Text
Comment
CDATASection
DocumentType
Notation
Entity
EntityReference
ProcessingInstruction
These specialized interfaces all inherit the basic attributes and methods provided
by the Nodeinterface. They also provide specialized access to unique information
associated with each specific XML document item. The resulting specialized
nodes are stored in a list of lists structure that has parent_child and
sibling-to-sibling links. For example, the following document in Example 3-5
would produce the tree of DOM nodes in memory shown in Figure 3-4 on
page 64. The structure can be traversed using the parent, child, and sibling links
available through the node interface.
Example 3-5 Sample XML document
<?xml version="1.0" encoding="UTF-8"?>
<Customer>
<name>Mary Smith</name>
<membership>10001</membership>
</Customer>
<Customer>
<name>Dave Johnson</name>
<membership>12345</membership>
</Customer>
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63
D o c u m e n t
E l e m e n t
E l e m e n t
E l e m e n t
T e x t
T e x t
E l e m e n t
E l e m e n t
E l e m e n t
T e x t
T e x t
Figure 3-4 Sample generated DOM tree
Document represents the whole documents, and the interface define methods for
creating elements, attributes, comments, and so on. Attributes of a Node are
manipulated using the methods of the Element interface. It should be noticed that
while a DOM application reads an XML document and an object representation is
formed, that representation remains only in memory. Changing a DOM object in
memory does not automatically modify the original file. That is something an
application program has to do for itself.
XML namespace support
The DOM Level2 supports XML namespace. It allows creating and manipulating
elements and attributes associated to a namespace. As far as the DOM is
concerned, special attributes used for declaring XML namespaces are exposed
and can be manipulated just like any other attribute. However, nodes are
permanently bound to namespace URIs as they get created. Consequently,
moving a node within a document, using the DOM, in no case results in a change
of its namespace prefix or namespace URI. Similarly, creating a node with a
namespace prefix and namespace URI, or changing the namespace prefix of a
node, does not result in any addition, removal, or modification of any special
attributes declaring the appropriate XML namespaces. Namespace validation is
not enforced; the DOM application is responsible.
DOM Level2 does not perform any URI normalization. The URIs given to the
DOM are assumed to be valid. Absolute URI references are treated as strings
and compared literally. How relative namespace URI references are treated is
undefined. To ensure inter operability, only absolute namespace URI references
should be used. Note that the empty string will be treated as a real namespace
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URI in DOM Level2 methods. Applications must use the value null as the
namespace URI parameter for methods if they wish to have no namespace.
3.5 JAXP
The Java API for XML Processing (JAXP) supports processing of XML
documents using DOM, SAX, and XSLT. JAXP enables applications to parse and
transform XML documents independent of a particular XML processing
implementation. Depending on the needs of the application, developers have the
flexibility to swap between XML Processors (such as high performance vs.
memory conservative parsers) without making application code changes. Thus,
application and tools developers can rapidly and easily XML-enable their Java
applications for e-commerce, application integration, and dynamic Web
publishing. Just added into the JAXP 1.2 reference implementation is support for
XML Schema and an XML compiler (XSLTC).
First released in March 2000, Sun’s JAXP 1.0 utilized XML 1.0, XML
Namespaces 1.0, SAX 1.0, and DOM Level 1. JAXP is a standard extension to
Java, meaning that SUn provides a specification through its Java Community
Process (JCP) as well as a reference implementation. JAXP 1.1 follows the same
basic design philosophies of JAXP 1.0, adding support for DOM Level2, SAX2,
and XSLT 1.0. A tool like JAXP is necessary because the XSLT specification
defines only a transformation language; it says nothing about how to write a Java
XSLT processor. Although they all perform the same basic tasks, every
processor uses a different API and has its own set of programming conventions.
So simply JAXP is an API, but it is more accurately an abstraction layer. It does
not provide a new means for parsing XML, add to SAX or DOM, or provide new
functionary to Java and XML handling. Instead, it makes it easier to deal with
some difficult tasks with DOM and SAX. Without SAX, DOM, or another XML
parsing API, you cannot parse XML.
The key to JAXP’s design is the concept of plug-ability. Figure 3-5 on page 66
illustrates the high-level architecture of JAXP. These layers provide consistent
Java interfaces to the underlying SAX, DOM, and XSLT implementations. In
order to utilize one of these APIs, you must obtain a factory class without
hard-coding Xalan or any other processor code in your application. This is
achieved via a lookup mechanism that relies on Java system properties. Since
three separate plug-ability layers are used, you can use a DOM parser from one
vendor, a SAX parser from another vendor, and yet another XSLT processor from
someone else. In reality, you will probably need to use a DOM parser compatible
with your XSLT processor if you try to transform the DOM tree directly.
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65
Application Code
JAXP
Transformer
SAXParser
DocumentBuilder
SAX Parser
Implementation
DOM API
Implementation
XSLT Processor
Implementation
Figure 3-5 JAXP architecture
As shown, application code does not deal directly with specific parser or
processor implementations. Instead, you write code against abstract classes that
JAXP provides. This level of indirection allows you to pick and choose among
different implementations without even recompiling your application.
Using JAXP
In this section, we show a very simple example that illustrates the usage of JAXP
to invoke the process of transforming an XML document, using an XSLT
stylesheet.
Example 3-6 Sample XML to HTML transformation code
File xml = new File("fileName.xml");
File xslt = new File("fileName.xsl");
File html = new File("fileName.html");
javax.xml.transform.Source xmlSource =
new javax.xml.transform.stream.StreamSource(xml);
javax.xml.transform.Source xsltSource =
new javax.xml.transform.stream.StreamSource(xslt);
javax.xml.transform.Result result =
new javax.xml.transform.stream.StreamResult(html);
//create an instance of TransformerFactory
javax.xml.transform.TransformerFactory transFact =
javax.xml.transform.TransformerFactory.newInstance();
javax.xml.transform.Transformer trans =
transFact.newTransformer(xsltSource);
trans.transform(xmlSource, result);
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Studying Example 3-6, notice that JAXP can read directly from a Fileobject, so
three files objects are created for the source XML, the XSLT stylesheet, and the
target HTML file. The Source interface is used to read both the XML file and the
XSLT file. The Source interface can have many implementations. In this example,
we are using StreamSource, which has the ability to read a File object, an
InputStream, a Reader, or a system ID. Later we will examine additional Source
implementations that use SAX and DOM as input. Just like Source, Resultis an
interface that can have several implementations. In this example, a StreamResult
sends the output of the transformations to a target file.
Next an instance of TransformerFactory is created. The TransformerFactoryis
responsible for creating Transformer and Template objects. In our example, we
create a Transformerobject. Transformerobjects are not thread-safe, although
they can be used multiple times. For a simple example like this, we will not
encounter any problems. In a threaded servlet environment, however, multiple
users cannot concurrently access the same TransformerFactoryinstance. JAXP
also provides a templates interface, which represents a stylesheet that can be
accessed by many concurrent threads.
The transformer instance is then used to perform the actual transformation. It
applies the XSLT stylesheet to the XML data, sending the result to the target file.
XSLT support packages in JAXP
JAXP support for XSLT is broken down into the packages listed below:
ꢀ javax.xml.transform: defines a general purpose API for XML
transformations without any dependencies on SAX or DOM. The Transformer
class is obtained from the TransformerFactory class. The Transformer
transforms from a source to a result.
ꢀ javax.xml.transform.dom: defines how transformations can be performed
using DOM. It also provides implementations of Source and Result:
DOMSource and DOMResult.
ꢀ javax.xml.transform.sax: supports SAX2 transformations. It defines SAX
versions of Sourceand Result: SAXSourceand SAXResult. It also defines a
subclass of TransformerFactory that allows SAX2 events to be fed into an
XSLT processor.
ꢀ javax.xml.transform.stream: defines I/O stream implementations of Source
and Result: StreamSourceand StreamResult.
The heart of JAXP XSLT support lies in the javax.xml.transformpackage,
which lays out the mechanics and overall process for any transformation that is
performed.
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67
Stylesheet compilation
Before a stylesheet can be processed, it must be converted into some internal
machine readable format. Usually the stylesheet is read into memory using an
XML parser, translated into machine format and then preserved in memory for
repeated use. This is called stylesheet compilation.
Different XSLT processors implement stylesheet compilation differently, so JAXP
includes the javax.xml.transform.Templates interface to provide consistency.
The newTransformer() method of this interface is widely used. It allows you to
obtain a new instance of a class that implements the Transformerinterface. It is
this Transformerobject that actually allows you to perform XSLT transformations.
Since the implementation of the Templatesinterface is hidden by JAXP, it must be
created by the following method on javax.xml.transform.TransformerFactory:
public Template newTemplates(Source source) throws
TransformeConfigurationException
As mentioned earlier, the Sourcemay obtain the XSLT stylesheet from one of
many locations, including a filename, a system identifier, or even a DOM tree.
Regardless of the original location, the XSLT processor is supposed to compile
the stylesheet into an optimized internal representation.
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4
Introduction to IBM
WebSphere Application
Developer
This chapter contains an introduction to the concepts behind Application
Developer, and an overview of the features of the various members of the
WebSphere Studio family of tools.
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69
4.1 WebSphere Studio product family
The WebSphere Studio family of products is built on the top of the Eclipse
Workbench as a set of plug-ins conforming to the Workbench’s open standard
APIs. These products are then follow-on technology for WebSphere Studio
Advanced Edition V3 and VisualAge for Java Enterprise Edition V4.
The WebSphere Studio family currently has the following members Figure 4-1:
ꢀ
ꢀ
ꢀ
ꢀ
WebSphere Studio Site Developer Advanced
WebSphere Studio Application Developer
WebSphere Studio Application Developer Integration Edition
WebSphere Studio Enterprise Developer
E n te rp r is e
D e v e lo p e r
E n te rp ris e
G e n e ra tio n
L a n g u a g e
z/O S , O S /3 9 0
s u p p o rt
S tru ts b a se d
M V C fra m e w o rk
W
e b S p h e re
S tu d io A s s e rt
A n a lyze r
D e v e lo p e r
R e s o u rc e P o ta l
A p p lic a tio n
D e v e lo p e r - IE
C o n n e c to r
s u p p o rt
C o n n e c to r
s u p p o rt
V is u a l flo w to o l
V isu a l flo w to o l
W
iz a rd s fo r
W
iza rd s fo r
c o m p le x e b
W
c o m p le x e b
W
S e rv ic e s a n d
E J B s
S e rvic e s a n d
E J B s
W
e b S p h e re A S
W
e b S p h e re A S
A p p lic a tio n
D e v e lo p e r
E E s u p p o rt
E E s u p p o rt
E J B c re a tio n
a n d d e p lo ym e n t
E J B c re a tio n
a n d d e p lo ym e n t
E J B c re a tio n
a n d d e p lo ym e n t
P e rfo rm a n c e
p ro fin in g a n d
a n a lys is to o ls
P e rfo rm a n c e
p ro fin in g a n d
a n a lys is to o ls
P e rfo rm a n c e
p ro fin in g a n d
a n a lys is to o ls
S ite D e v e lo p e r
A d v a n c e d
W
e b S e rv ice
W
e b S e rv ic e
W
e b S e rv ic e
W
e b S e rv ic e
w iz a rd
w iza rd
w iz a rd
w iza rd
W
S tu d io
H o m e p a g e
B u ild e r
e b S p h e re
J S P a n d s e rv le t
c re a tio n
Te a m
E n v iro n m e n t
J S P a n d s e rv le t
c re a tio n
Te a m
E n v iro n m e n t
J S P a n d s e rv le t
c re a tio n
Te a m
E n viro n m e n t
J S P a n d se rv le t
c re a tio n
Te a m
E n v iro n m e n t
X M L to o ls
X M L to o ls
X M L to o ls
X M L to o ls
D a ta b a se w iza rd
C o re J a v a ID E
D a ta b a s e w iza rd
C o re J a v a ID E
D a ta b a s e w iza rd
C o re Ja v a ID E
D a ta b a s e w iz a rd
C o re J a v a ID E
W
e b S p h e re
W
e b p a g e
W
e b p a g e
W
e b p a g e
S tu d io
W
e b p a g e
w iz a rd s a n d
d y n a m ic e ffe c ts
w iza rd s a n d
d yn a m ic e ffe c ts
w iz a rd s a n d
d yn a m ic e ffe cts
P ro fe s s io n a l
w iza rd s a n d
d yn a m ic e ffe c ts
IB M W e b S p h e re S tu d io F a m ily
Figure 4-1 WebSphere Studio family
These products provide support for end-to-end development, testing, and
deployment of Web and J2EE applications.
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The WebSphere Studio family of products provide integrated development tools
for all e-business development roles including Web developers, Java developers,
business analysts, architects, and Enterprise programmers. The customizable,
targeted and role-based approach of the Workbench will be a common
characteristic of future products in the WebSphere Studio family.
WebSphere Studio Site Developer Advanced
Site Developer Advanced is an IDE intended for Web developers who develop
and manage complex Web sites. It is an easy-to-use toolset that minimizes the
time and effort required to create, manage, and debug multi-platform Web sites.
It is designed according to the J2SE and J2EE specifications, and supports
JSPs, servlets, HTML, JavaScript, and DHTML. It further includes tools for
developing images and animated GIFs.
Site Developer Advanced enables Web developers to use their favorite content
creation tools in conjunction with the built-in local and remote publishing
capabilities.
Using Site Developer Advanced, you can develop Web applications that use the
following technologies.
ꢀ
JSPs: A simple, fast and consistent way to extend Web server functionality
and create dynamic Web content. JSPs enable rapid development of Web
applications that are server and platform-independent.
ꢀ
ꢀ
Servlets: Server code that executes within a Web Application Server.
Web services: Self-contained, modular applications that can be described,
published, located, and invoked over the Internet or within intranets.
WebSphere Studio Application Developer
Application Developer is designed for professional developers of Java and J2EE
applications, who require integrated Web, XML, and Web services support.
It includes all of the features of Site Developer Advanced, and adds tools for
developing EJB applications, as well as performance profiling and logging tools
for both local and remote execution.
Developers can quickly build and test business logic and enhance the
presentation artifacts with built-in Web creation tools inside the Application
Developer IDE before deploying to a production server.
Using the performance profiling and tracing tools makes it possible to detect
application performance bottlenecks earlier in the development cycle.
Furthermore, the built-in test environment for WebSphere Application Server and
advanced tools for code generation help to shorten the test cycle.
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71
WebSphere Studio Application Developer Integration Edition
Integration Edition includes all of the functionality in Application Developer, plus:
ꢀ
Powerful graphical tools to help you quickly and easily build custom
application adapters to integrate your J2EE application with your back-end
systems, helping you save time and money by reusing existing resources.
ꢀ
Visual flow-based tools that increase developer productivity by allowing them
to visually define the sequence and flow of information between application
artifacts such as adapters, Enterprise JavaBeans components, and Web
services.
ꢀ
ꢀ
Wizards that help in building and deploying complex Web services out of
adapters, EJB components, flows, and other Web services.
Support for the full set of Enterprise services provided by WebSphere
Application Server Enterprise Edition such as Business Rule Beans,
internationalization, and work areas that deliver additional integration
capabilities, developer productivity, and business agility.
WebSphere Enterprise Developer
Enterprise Developer includes all of the functionality in WebSphere Studio
Application Developer Integration Edition, plus:
Enterprise Developer can be used to implement Struts-based MVC applications
using connectors and the Enterprise Generation Language (EGL).
The ability to connect components is the first step in modernizing the application
portfolio of Enterprises. It supports creating and connecting Web applications to
Enterprise business logic using the Struts-based Model-View-Controller
framework and associated tooling.
Two other core technologies are integrated within Enterprise Developer.
ꢀ
ꢀ
WebSphere Studio Asset Analyzer (WSAA): Identifies application
processes and connecting points, and provides the ability to generate
components from existing code
Developer Resource Portal (DRP): Provides collaborative capabilities
across the entire development process
Enterprise Developer addresses the needs of large Enterprises, providing a
model based paradigm for building applications in a Struts-based
Model-View-Controller framework. It provides a visual construction and assembly
based environment supporting the implementation of Enterprise level
applications, including support for the multiple developer roles and technologies
required by those applications. Some examples of technologies supported are
HTML, JSPs, servlets, EJBs, COBOL, EGL, PL/I, and connectors.
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4.2 Tools
The WebSphere Studio family of products includes the following basic tools:
ꢀ
Web development tools
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Relational database tools
XML tools
Java development tools
Web services development tools
Team collaboration tools
Integrated debugger
Server tools for testing and deployment
Enterprise JavaBean development tools (not in Site Developer Advanced)
Performance profiling tools (not in WSSD)
Plug-in development tools
4.2.1 Web development tools
The professional Web development environment provides the necessary tools to
develop sophisticated Web applications consisting of static HTML pages, JSPs,
servlets, XML deployment descriptors, and other resources.
Wizards are available to generate running Web applications based on SQL
queries and JavaBeans. Links between Web pages can be automatically
updated when content changes. There are also tools for creating images and
animated GIFs.
The Web development environment bring all aspects of Web application
development into one common interface. Everyone on your Web development
team including content authors, graphic artists, programmers, and Web masters,
can work on the same projects and access the files they need.
Such an integrated Web development environment makes it easy to
collaboratively create, assemble, publish, deploy, and maintain dynamic,
interactive Web applications.
The Web development tools provide the following features:
ꢀ
ꢀ
Support for latest Web technology with an intuitive user interface
Advanced scripting support to create client-side dynamic applications with
VBScript or JavaScript
ꢀ
ꢀ
Web Art Designer to create graphic titles, logos, buttons, and photo frames
with professional-looking touches
Animated GIF designer to create life-like animation from still pictures,
graphics, and animated banners
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ꢀ
ꢀ
Over 2,000 images and sounds in the built-in library
Integrated, easy-to-use visual layout tool for JSP and HTML file creation and
editing
ꢀ
ꢀ
Web project creation, using the J2EE-defined hierarchy
Creation and visual editing of the Web application deployment descriptor
(web.xml) file
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Automatic update of links as resources are moved or renamed
A wizard for creating servlets
Generation of Web applications from database queries and JavaBeans
J2EE WAR/EAR deployment support (not in Site Developer Advanced)
Integration with the WebSphere unit test environment
4.2.2 Relational database tools
The database tools provided with the WebSphere family products allow you to
create and manipulate the data design for your project in terms of relational
database schemas.
You can explore, import, design, and query databases working with a local copy
of an already existing design. You can also create an entirely new data design
from scratch to meet your requirements.
The database tools provide a metadata model that is used by all other tools that
need relational database information. This includes database connection
information. In that way tools, although that unaware of each other are able to
share connections.
The SQL statement wizard and SQL query builder provide a GUI-based interface
for creating and executing SQL statements. When you are satisfied with your
statement, you can use the SQL to XML wizard to create an XML document, as
well as XSL, DTD, XSD, HTML, and other related artifacts.
The relational database tools support connecting to, and importing from several
database types including DB2, Oracle, SQL Server, Sybase, and Informix.
4.2.3 XML tools
The comprehensive XML toolset provided by the WebSphere Studio family of
products includes components for building DTDs, XML Schemas, and XML files.
With the XML tools, you can perform all of the following tasks:
ꢀ
Create, view, and validate DTDs, XML Schemas, and XML files.
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ꢀ
ꢀ
ꢀ
Create XML documents from a DTD, from an XML Schema, or from scratch.
Generate JavaBeans from a DTD or XML Schema.
Define mappings between XML documents and generate XSLT scripts that
transform documents.
ꢀ
ꢀ
ꢀ
Create an HTML or XML document by applying an XSL style sheet to an XML
document.
Map XML files to create an XSL transformation script and to visually step
through the XSL file.
Define mappings between relational tables and DTD files, or between SQL
statements and DTD files, to generate a document access definition (DAD)
script, used by IBM DB2 XML Extender. This can be used to either compose
XML documents from existing DB2 data or decompose XML documents into
DB2 data.
ꢀ
Generate DADX, XML, and related artifacts from SQL statements, and use
these files to implement your query in other applications.
4.2.4 Java development tools
All WebSphere Studio family of products provide a professional-grade Java
development environment with the following capabilities:
ꢀ
ꢀ
Application Developer v5.0 ships with JDK 1.3
Pluggable run-time support for JRE switching and targeting of multiple
run-time environments from IBM and other vendors
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Incremental compilation
Ability to run code with errors in methods
Crash protection and auto-recovery
Error reporting and correction
Java text editor with full syntax highlighting and complete content assist
Refactoring tools for reorganizing Java applications
Intelligent search, compare, and merge tools for Java source files
Scrapbook for evaluating code snippets
4.2.5 Web services development tools
Web services represent the next level of function and efficiency in e-business.
Web services are modular, standards-based e-business applications that
businesses can dynamically mix and match in order to perform complex
transactions with minimal programming. The WebSphere Studio family of
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products that include the Web services feature, help you to build and deploy Web
services-enabled applications across the broadest range of software and
hardware platforms used by today's businesses. These tools are based on open,
cross-platform standards such as Universal Description Discovery and
Integration (UDDI), Simple Object Access Protocol (SOAP), and Web Services
Description Language (WSDL).
4.2.6 EJB development tools
The WebSphere Studio family (except Site Developer Advanced) feature full EJB
support (Application Developer v5.0 supports EJB2.0 and EJB 1.1), an updated
EJB test client, an enhanced unit test environment for J2EE, and deployment
support for Web application archive (WAR) files and Enterprise application
archive (EAR) files. Entity beans can be mapped to databases, and EJB
components can be generated to tie into transaction processing systems. XML
provides an extended format for deployment descriptors within EJB.
4.2.7 Team collaboration
Team developers do all of their work in their individual workbenches, and then
periodically make changes to a team stream. This model allows individual
developers to work on a team project, share their work with others as changes
are made, and access the work of other developers as the project evolves. At any
time, developers can update their work space by retrieving the changes that have
been made to the team stream or by submitting changes to the team stream.
All products of the WebSphere Studio family support the Concurrent Versions
System (CVS) and the Rational ClearCase LT products among others.
Other software configuration management (SCM) repositories can be integrated
through the Eclipse Workbench SCM adapters. SCM adapters for commercial
products are provided by the vendors of those products.
4.2.8 Debugging tools
The WebSphere Studio family products include a debugger that enables you to
detect and diagnose errors in your programs running either locally or remotely.
The debugger allows you to control the execution of your program by setting
breakpoints, suspending launches, stepping through your code, and examining
the contents of variables.
You can debug live server-side code as well as programs running locally on your
workstation.
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The debugger includes a debug view that shows threads and stack frames, a
process view that shows all currently running and recently terminated processes,
and a console view that allows developers to interact with running processes.
There are also views that display breakpoints and allow you to inspect variables.
4.2.9 Performance profiling tools
The WebSphere Studio family except Site Developer Advanced provide tools that
enable you to test the performance of your application. This allows you to make
architectural and implementation changes early in your development cycle, and
significantly reduces the risk of finding serious problems in the final performance
tests.
The profiling tools collect data related to a Java program's run-time behavior, and
present this data in graphical and non-graphical views. This assists you in
visualizing program execution and exploring different patterns within the
program.
These tools are useful for performance analysis, and for gaining a deeper
understanding of your Java programs. You can view object creation and garbage
collection, execution sequences, thread interaction, and object references. The
tools also shows you which operations take the most time, and help you find and
plug memory leaks. You can easily identify repetitive execution behavior and
eliminate redundancy, while focusing on the highlights of the execution.
4.2.10 Server tools for testing and deployment
The server tools provide a unit test environment where you can test JSPs,
servlets and HTML files, (EJB testing is supported in Application Developer and
Enterprise Developer). You also have the capability to configure other local or
remote servers for integrated testing and debugging of J2EE applications.
The following features are included:
ꢀ
A copy of the complete WebSphere Application Server Developer Edition
(AEs) run-time environment
ꢀ
ꢀ
ꢀ
Stand-alone unit testing
Ability to debug live server-side code using the integrated debugger
Support for configuring multiple servers
The server tools support the following run-time environments:
ꢀ
WebSphere Application Server AEs, which can be installed locally or
remotely. It supports testing of both EJBs and Web applications.
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ꢀ
Apache Tomcat, which can be installed only locally and supports testing of
Web applications.
4.2.11 Plug-in development tools
The WebSphere Studio family (except for Site Developer Advanced) include the
PDE (Plug-in Development Environment) which is designed to help you develop
platform plug-ins while working inside the platform workbench, and it provides a
set of platform extension contributions (views, editors, perspectives, etc.) that
collectively streamline the process of developing plug-ins inside the workbench.
The PDE is not a separate tool, but it is a one of perspectives. PDE blends with
the platform and offers its capabilities through a new perspective.
The following project types are supported:
ꢀ
Plug-in project
WebSphere Studio Application Developer is based on the concept of plug-ins,
which have a clearly defined structure and specification. This project supports
creating, testing , and deploying a plug-in in the PDE.
ꢀ
Fragment project
A plug-in fragment is used to provide additional plug-in functionality to an
existing plug-in after it has been installed. Fragments are ideal for shipping
features like language or maintenance packs, which typically trail the initial
products by a few months.
ꢀ
Plug-in component
PDE attaches a special component nature to plug-in and fragment projects to
differentiate them from other project types. The project must have a specific
folder structure and a component manifest. The project must be set up with
references to all of the plug-in and fragment projects, which will be packaged
into the component.
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5
Application Developer XML
Tools
Chapter four introduces the XML development capabilities of Websphere
Application Developer. In particular, the chapter covers the following topics:
ꢀ
ꢀ
ꢀ
XML perspective
XML editors
XML support features in Websphere Studio Application Developer
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5.1 XML perspective
Perspectives are a way to look through different views to a a project. Depending
on the role of the developer (whether a Web developer, or a Java developer, or an
EJB developer, etc.). And also depending on the tasks that the developer must
perform, the developer uses a different perspective. The XML perspective is the
perspective for XML development in the Application Developer. It contains
several editors and views that can help a developer in building XML files, XML
Schemas, DTDs, stylesheets, and integrating between data extracted from
relational databases and XML. To open the XML perspective select
Window—>Open Perspective—>XML
Figure 5-1 XML perspective
The XML perspective (Figure 5-1) contains four sections:
ꢀ
The view on the top left of the perspective shows the Outline view for the
active editor; in this case the XML editor is active.
ꢀ
The view on the top right shows the active editors
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ꢀ
ꢀ
The view on the bottom left shows the Navigator view, which displays the
folders, and files of the project
The view on the bottom right shows the Tasks view, which shows the
problems and errors to be fixed
5.2 XML perspective editors
In this section, we demonstrate the editing capabilities of the XML components
editors available in the Application Developer.
5.2.1 XML editor
This is a tool for creating and viewing XML files. You can use it to edit the
contents of new XML files, either created from scratch or from existing DTDs, or
XML Schemas. You can also use it to edit XML files, associate them with DTDs
or schemas, and validate them.
Creating an XML file from scratch
In this section, we show how to create a new XML file. To create a new file from
scratch, use the New XML wizard as follows:
ꢀ
Select File—>New—>Project—>Simple —>Project to bring up the New
Project wizard to create a simple project.
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Select File—>New—>XML to launch the new XML wizard.
Select the option Create XML file from scratch.
Select Next.
In the File name field, type your XML file name.
Click Finish. The XML file is created and the XML Editor is automatically
opened for you, as shown in Figure 5-2.
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Figure 5-2 XML editor
Editing an XML file
The XML Editor has two main views: Source view, Design view, in addition to
utilizing the Outline view, and Task view. The Source view is a text editor that lets
you directly edit the source of the XML document. It has several text editing
features, such as syntax highlighting, and content assist, which uses the
information in a DTD or schema content model to provide a list of acceptable
continuations depending on where the cursor is located in an XML file, or what
has just been types. The XML editor Source view also includes a smart
double-clicking behavior. If your cursor is placed in an attribute value, one
double-click selects that value, another double-click selects the attribute-value
pair, and a third double-click selects the entire tag. This makes it easier to copy
and paste commonly used pieces of your XML code.
The Design view displays the XML document as a tree enabling you to
manipulate the document by adding, removing, and editing tree nodes. This also
makes navigation easier. Note that in the left column of the Design view, we see
the elements, attributes, and other nodes of the XML document's tree. The right
column is used to display the values associated with these nodes. Content and
attribute values can be edited directly in the table cells, while right-click menus on
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the tree nodes give alternatives that are valid for that location. The right column is
also used to display content model information associated with elements.
The Outline view provides an overview of the XML document that can be useful
when navigating large documents. And finally the Task view displays error
messages that may be associated with the XML document.
Note the editor's page tabs at the bottom of the top right pane. These tabs are
used to switch between the Design view and the Source view of the XML Editor.
The views are synchronized so that a change made in one view will be
automatically reflected in the other view.
Validating the XML file
Another useful feature of the XML editor is the incremental validation feature. At
any point during your development of an XML document, you can invoke the
validate process to validate the file. Just right-click on the file name in the
Navigator view, and select Validate XML File option. In addition to the manual
invocation of the validation process, the validation is also automatically run when
you save the document, or when you finish typing in the Source view (as
indicated by switching focus to a different view). Any validation errors will be
reported in the Task view with a little red marker for the corresponding line in the
Source view and the corresponding object in the Outline view.
5.2.2 DTD editor
This is a tool for creating and viewing DTDs. You can use it to edit the contents of
new DTD files, either created from scratch or from existing XML Schemas. You
can also use it to edit existing DTD files, and validate them.
Creating a DTD from scratch
In this section, we show how to create a new DTD file. To create a new DTD from
scratch, use the New DTD wizard as follows:
ꢀ
Project wizard to create a simple project.
ꢀ
ꢀ
ꢀ
Select File—>New—>DTD to launch the New DTD wizard.
In the File name field, type your DTD file name.
Click Finish. The DTD file is created and the DTD editor is automatically
opened for you, as shown in Figure 5-3 on page 84.
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Figure 5-3 DTD Editor
In order to handle the contents of a DTD file, you can use the Outline view to add
or remove components of your DTD. When you select an object in the Outline
view, the Design view will display the properties that are associated with that
DTD component object. You can use the Design view to enter values for the
selected object. You can switch to the Source view to edit the DTD source
directly. The DTD editor also uses the Task view from the workbench for errors
reporting.
Using the Outline view to add DTD components
The DTD specification defines a large number of components such as elements,
entities, notations, comments, attributes, etc. To create a valid DTD, you must
understand the containment relationships between these components.The XML
Schema Editor removes the burden to remember these details for you. You can
use the Outline view to add DTD components via the pop-up menu as shown in
Figure 5-4 on page 85. The pop-up menu will only display the list of objects that
are relevant for the selected object. It will also add the object at the correct
location in the DTD.
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Figure 5-4 Pop-up on DTD file in the Outline view
Validating DTD
Another useful feature of the DTD editor is the incremental validation feature. At
any point during your development of a DTD, you can invoke the Validate process
to validate the DTD. Just right-click on the file name in the Navigator view, and
select Validate DTD option. In addition to the manual invocation of the validation
process, the validation is also automatically run when you save the document, or
when you finish typing in the Source view (as indicated by switching focus to a
different view). Any validation errors will be reported in the Task view with a little
red marker for the corresponding line in the Source view and the corresponding
object in the Outline view.
5.2.3 XSD editor
An XML Schema editor is a tool for creating, viewing, and validating XML
Schemas. You can use the XML Schema editor to perform tasks such as creating
XML Schema components, importing and viewing XML Schemas.
Creating a schema from scratch
In this section, we show how to create a new XML Schema. To create a new
schema from scratch, use the New XML Schema wizard as follows:
ꢀ
Project wizard to create a simple project.
ꢀ
ꢀ
ꢀ
Select File—>New—>XML Schema to launch the New XML Schema wizard.
In the File name field, type your schema file name.
Click Finish. The schema file is created and the XML Schema Editor is
automatically opened for you, as shown in Figure 5-5 on page 86.
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Figure 5-5 XML Schema Editor
In order to handle the contents of a schema file, you can use the Outline view to
add, remove, or rearrange components of your schema. When you select an
object in the Outline view, the Design view will display the properties that are
associated with that schema component object. you can use the Design view to
enter values for the selected object. You can switch to the Source view to edit the
schema source directly. The XML Schema editor also uses the Task view from
the workbench for errors reporting.
Using the Outline view to add schema components
The XML Schema specification defines a large number of components such as
schema, complexType, simpleType, group, annotation, include, import, element,
and attribute, etc. To create a valid schema, you must understand the
can only be added to a complex type, but not a simple type. A group can only be
defined at the schema level, but can be referenced by a complex type, etc.
The XML Schema editor removes the burden to remember all these details for
you. You can use the Outline view to add schema components via the pop-up
menu, as shown in Figure 5-6 on page 87. The pop-up menu will only display the
list of objects that are relevant for the selected object. It will also add the object at
the correct location in the XML Schema.
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Figure 5-6 Pop-up on schema file in the Outline view
Making changes and referential integrity
As a schema becomes bigger and more complex, there will be more type
definitions, and references to those types. So what happens after you have
defined a type, created ten references to that type, and you want to change the
name of the type? The XML Schema editor has a built-in referential integrity
mechanism that will propagate the changes automatically, freeing you from the
tedious and error-prone task of doing the manual updates.
Let us assume that in your xsd file, you have defined a simple type called
SimpleType1. There is a reference to this type in the complex type named
ComplexType1. Let us say we want to change the simple type name from
SimpleType1 to SimpleType2.The following illustrates how to do that:
ꢀ
ꢀ
Switch to the Design view.
Select the SimpleType1 in the Outline view. In the Design view, change it to
SimpleType2.
ꢀ
Now switch over to the Source view. Notice how all references to SimpleType1
change to SimpleType2 automatically.
The XML Schema editor's referential integrity mechanism is not limited only to
name change. The same rule applies when you delete a schema component. For
example, if you delete a type, all references to that type will automatically be
reset to the default string data type. Whenever such an automatic update occurs,
an information message will be displayed in the Task view. You can always invoke
the undo action if you want to change your mind.
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One thing to note is that the built-in referential integrity mechanism will only be
enforced if the change is made from the Design view. If you make the changes
directly by typing in the Source view, then it is your responsibility to ensure that
you make all the changes correctly. Any change you made in the Source view will
automatically be reflected in the Design and Outline view.
Namespace
Namespace provides a way to identify where an element or attribute comes from.
For example, two elements from two different schemas might have the same
name (for example, SampleElement). To identify them, let us say Schema A's
SampleElement vs. Schema B's SampleElement; we can use the XML
Namespaces mechanism to distinguish them.
This section provides a quick introduction on how to define namespace for your
schema in the XML Schema editor. In the xsd file, the target namespace is by
default is http://www.ibm.com. This is indicated by the targetNamespace
attribute in the schema element. This means that all the types that are defined in
this schema belong to the target namespace http://www.ibm.com.
Usually, your schema has a prefix for its target namespace. To refer to any type
defined in your schema, you must use this defined prefix. If you want to change
the namespace prefix or the target namespace for your schema, you can use the
Design view to do this. The following demonstrates this feature:
ꢀ
ꢀ
ꢀ
Select the file object, that is your schema.
In the Design view, change the Prefix field to any prefix you desire.
In the Design view, change the Target namespace field to any namespace of
your choice, for example http://www.your application name.com.
ꢀ
Because such a change has a global impact to your entire document, you
schema element and all the prefixes for the types are automatically changed
for you.
In order to have a more detailed view about XML namespaces and their support
in the Application Developer, have a look at 5.3, “Namespace support” on
page 90.
Validating schema
Another useful feature of the XML Schema editor is the incremental validation
feature. At any point during your development of an XML Schema, you can
invoke the validate process to validate the schema. The validation is also
automatically run when you save the document, or when you finish typing in the
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Source view (as indicated by switching focus to a different view). Any validation
errors will be reported in the Task view with a little red marker for the
corresponding line in the Source view, and the corresponding object in the
Outline view.
Also, when making changes in the Design view, pay attention to the status bar. It
will contain hints for potential errors in the schema that you are developing.
5.2.4 XSL editor
This is a tool for creating and viewing XSL files. You can use it to edit the
contents of new XSL files created from scratch. Moreover, you can also use it to
edit existing ones that are created using the XML to XML mapping wizard.
Creating an XSL file from scratch
scratch, use the New XSL wizard as follows:
ꢀ
ꢀ
ꢀ
Select File—>New—>XSL to launch the New XSL wizard.
In the File name field, type your XSL file name.
Click Finish. The XSL file is created and the XSL editor is automatically
opened for you, as shown in Figure 5-7.
Figure 5-7 XSL editor
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Editing an XSL file
The XSL editor provides a text editor to handle the source code of the XSL file. It
has several text editing features, such as content assist and syntax highlighting.
The content assist feature helps you in writing you XSL code, as it is aware of the
proper XSL grammar rules. When editing the XSL document, content assist can
be invoked to prompt the you with a list of possible XSL constructs to use.
Concerning the syntax highlighting feature, you will notice that whenever you
select any of the XSL file components listed in the Outline view, the
corresponding XSL code for that component will be selected, and vice versa.
Validating the XSL file
Another useful feature of the XSL editor, like the rest of the editors, is the
incremental validation feature. At any point during your development of an XSL
file, you can invoke the Validate process to validate the file. Just right-click on the
file name in the Navigator view, and select the Validate XSL File option. In
addition to the manual invocation of the validation process, the validation is also
automatically run when you save the document. Any validation errors will be
reported in the Task view with a little red marker for the corresponding line in the
source code of the XSL file.
5.3 Namespace support
Namespaces are useful when there is a need for elements and attributes of the
same name to take on different meaning depending on the context in which they
are used. So, the XML namespace is the means to distinguish between elements
that have the same name but come from different problem domain. An XML
Schema supports namespaces.
Let us say for example we are taking about an attribute called Name. It will can
have different meanings depending on whether it is applied to a customer, or
flight carrier. If both entities (a customer and a flight carrier) need to define the
same document such as in a flight entry, which associates a flight with its
corresponding information, and the list passengers on that flight. We need some
mechanism to distinguish between the two, and apply the correct semantic
description for the attribute name, whenever it is used in the document.
Namespaces provide the mechanism that allows us to write XML documents that
contain information relevant to the problem domain.
To include your namespace information into your XML file when creating your
XML document, select the option Create XML file from an XML Schema file,
which specifies the namespace information. When you do that, the target
namespace and prefix from the XML Schema file is automatically picked up when
creating the document.
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If you review the generated XML file, you will notice that the root element is
qualified to belong to the target namespace specified in the schema file. It is also
important to note that the local elements that belong to the root element are
default specifies that local elements should not be qualified.
In order to qualify all the local elements in an XML document, the XML Schema
must set the elementFormDefaultattribute to qualified in the schema element.
This can be accomplished by selecting Qualified in the Element form default
field of the Design view for the schema, as shown in Figure 5-8. All XML files
created from this schema will have all the elements qualified with the namespace
prefix.
Figure 5-8 Indicate all local elements to be qualified.
When you use the XML Schema editor to create your schema file by default, the
target namespace for this schema is http://www.ibm.comas indicated by the
target namespace attribute, as shown in Figure 5-8. If you do not specify a prefix
in the prefix field for the schema object, then you are making the default
namespace for this schema to be the same as the target namespace. When you
click the Apply button, you will notice that the xmlns attribute is added to the
schema tag to indicate that the default namespace of this schema is
http://www.ibm.com. You will also notice that the XML Schema constructs will
automatically be qualified with the prefix xsdto distinguish them from the types
that are in the default namespace. By making the target namespace of this
schema the default namespace, you do not have to qualify types from this
schema when you reference them.
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5.4 XPath support
XPath is an XSL sub-language that is designed to be used with XSLT. It is used
for identifying or addressing parts of a source XML document. Every node within
an XML document can be uniquely identified and located using the syntax
defined for XPath.
WebSphere Application Developer provides support for XPath. To launch the
XPath Builder
ꢀ
ꢀ
ꢀ
Move to the XML perspective.
Choose an XML file in your project.
Right-click, and select Generate —>XPath.
Figure 5-9 XPath Builder
In order to define your XPath, the Application Developer provides you with means
for defining all the necessary constructs. Look at Figure 5-10. After you choose
the desired node in your XML tree, you will need to provide the steps for the
location paths. Although location paths are not the most general grammatical
construct in the language, they are the most important construct. A location path
selects a set of nodes relative to the context node. The result of evaluating an
expression that is a location path, is the node-set containing the nodes selected
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by the location path. Location paths can recursively contain expressions that are
used to filter sets of nodes. A location path has three steps:
1. An axis, which specifies the tree relationship between the nodes selected by
the location step and the context node.
2. A node test, which specifies the node type and expanded-name of the nodes
selected by the location step.
3. Zero or more predicates, which use arbitrary expressions to further refine the
set of nodes selected by the location step.
Figure 5-10 XPath definition
After you finish with the location paths, the next tab allows the usage of a
operators, as shown in Figure 5-11. This wizard provides you with a list of
node-set operators, boolean operators, and numeric operators. Expanding any
on the list will show the available operators, from which you can select your
choice.
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Figure 5-11 XPath Operators
The last tab shows a list of functions to use in your XPath definition, as shown in
Figure 5-12. There is a list of node set functions, boolean functions, string
functions, number functions, XSLT functions.
After you finish defining your XPath, you can click the Execute button to test your
XPath. The wizard displays your XPath results, as shown in Figure 5-13.
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Figure 5-13 XPath Query Result screen
5.5 XSL debugger
This tool enables you to visually step through an XSL transformation script,
highlighting the transformation rules as they are fired. It is used to test the
generated XSL style sheet. Simply use the editor to apply the XSL style sheet to
a source XML file, and create a new HTML or XML file. You can then trace
through the new XML or HTML file to verify if the results are correct.
The XSL trace editor only works on a one-to-one basis. You can only apply an
XSL file to one XML file at a time if you want to use the XSL trace editor to trace
XSL file to an XML file, and trace the results.
So, to invoke the XSL debugging process, select your XML file to be transformed,
and XSL file in the Navigator view, then invoke the trace from the context menu
by selecting Apply XSL—>As HTML. The trace editor presents the input XML,
and the input XSL, as shown in Figure 5-14. You can replay the transform using
stepping controls in the toolbar. As the transform is applied, the trace editor
highlights each XSL statement, and the XML input element it matches, allowing
you to understand and resolve any problems.
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Moreover, the XSL debugger allows to add breakpoints to your XSL file, which
facilitate the debugging process. To add a breakpoint, just double click on the line
number where you want to place the breakpoint, and green ball will appear
breakpoint, choose the breakpoints tab in the window in the upper right hand
corner shown in Figure 5-14. Just select the breakpoint you want to remove, and
right-click, selecting the Remove option from the context menu.
The buttons in the Sessions window (in the top left hand corner shown in
Figure 5-14) allow you to handle your debugging process. They provide features
like step forward or step backward in the result document; restart the process
from the beginning; run to breakpoint; and open the browser on the
transformation result.
To close the XSL debugger, simply close the XSL debug perspective, or switch to
any other perspective you desire.
Figure 5-14 XSL Debugger
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5.6 Web services support
XML and its associated family of standards play a central role in Web services by
providing a data interchange format that is independent of both programming
languages and operating systems. This section gives an overview of the support
provided by the Application Developer for XML-based Web services. For detailed
information about the development of XML Web services using Websphere
Studio Application Developer, please refer to Chapter 9. Please note that we
assume you already have a background about Web services.
To start developing your Web service, you will need to create a Web project in
your work space to contain the Web service. To implement your XML Web
service, the Application Developer provides you with the two very important
wizards to use.
Web Service DADX group configuration wizard
DAD extension (DADX) is an extension of the DB2 XML Extender document
access definition (DAD) file. A DADX document specifies how to create a Web
service using a set of operations that are defined by SQL statements or DAD
files. DAD files are files that describe the mapping between XML documents
elements and DB2 database columns. They are used by the DB2 XML Extender,
which supports XML-based operations that store or retrieve XML documents to
and from DB2 database.
The Web services DADX group configuration wizard enables you to create a
DADX group. The DADX group created with this wizard is used to store DADX
documents. A DADX group contains connection (JDBC and JNDI) and other
information that is shared between DADX files.
Once you have created a DADX group, you can import DADX files and then start
the Web services wizard to create a Web service from a DADX file. A DADX file
is created using the XML from SQL query wizard.
Web service wizard
This wizard is used for creating Web services. It is cable of generating several
types of Web services. The focus of this book is only on DADX Web services.
Using the wizard, you can specify to generate a Web service proxy class. A Web
service proxy class makes it very easy to invoke a Web service. You just
instantiate the class and invoke the desired method on it.
Moreover, the wizard gives you the ability to generate and invoke a sample
application. The sample application is a small Web application, which enables
you to invoke the different methods of the Web service, and to view the results.
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The generated sample contains the code to instantiate the generated Web
service proxy class and to invoke the desired methods on it.
You can specify to immediately launch the sample application after the wizard. A
default Websphere test environment is started, and the test client starts in a
browser, and you can test the Web service.
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RDB and XML integration
Chapter six discusses XML and SQL capabilities within Application Studio. In any
application, simple or complex, a database usually acts as the data store. For
any application development tool, whether developing the graphical user
interface or the business logic components, an easy to use tool graphical tool
that works well with a database is a must. Application Studio’s tool and wizards
for interacting with the database provide a multitude of capabilities.
The SQL to XML wizards gives the user the capability of generating eXtensible
Style Sheet (XSL) and XML files from a SQL statement. In the chapter, a simple
schema was created to demonstrate the various file generation capabilities. The
files from the different options are hen compared.
The DB2 XML Extender is discussed in 6.4, “DB2 XML Extender” on page 126. A
very broad overview is provided with the two methods used for storing XML data
in the DB2 database. A comparison is carried between the two methods with
recommendations for using each method in a set of conditions.
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6.1 The SQL to XML wizards
The SQL to XML wizards are found in the data perpective. To demonstrate the
wizards and the files produced, a schema and SELECT statement has to be
created. The schema is shown below in Figure 6-1. It consists of three tables:
PASSENGER, SCHEDULE, and AIRCRAFT. The PASSENGER and
SCHEDULE tables are joined by the flight and flightNo attributes. The aircraft
attribute on the SCHEDULE table is connected to the aircraft_key attribute on the
AIRCRAFT table through a foreign key.
Figure 6-1 The Passenger List Select statement
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To generate the XML relate files based on the Passenger List Select statement,
right-clink on the selectPassengerList statement, and select the Generate new
XML from the pop-up menu. The SQL to XML wizard opens as shown below:
Figure 6-2 The SQL to XML wizard panel
The wizard provides three options (Figure 6-2). The last Output folder is
automatically filled in if there is only one project and if that project has been
pre-selected. Other projects can be selected by clicking the Browse button.
The first option Show table columns as produces three files. To view the files, the
user has to navigate through to the Navigator view. We will compare these files
with the different options further below. Through the second option, Generate
schema definition as, we can opt to produce a XML Schema file, or a DTD,
or none of these.
The third option, Save query gives us the option to generate a query template file
with the name of the template file already defined from the select statement. This
name can be changed, if so desired.
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Show table column as option
This option produces three files for each select statement. Accordingly, they are
named after the select statement, and in our example their names are:
ꢀ
ꢀ
ꢀ
The selectPassengerList.html
The selectPassengerList.xml
The selectPassengerList.xsl
The most important files here are the XML and XSL files, because the HTML file
can also be generated from these two files. To generate the HTML file, select
both of them, right-click, and from the pop-up menu, select Apply XSL, and then
select As HTML.
If the Recurse through foreign keys check box is ticked, another three files are
produced:
ꢀ
ꢀ
ꢀ
The selectPassengerList_AIRCRAFT.html
The selectPassengerList_AIRCRAFT.xml
TheselectPassengerList_AIRCRAFT.xsl
However, this only works if the Foreign key as links option is chosen. For the
other three options, ticking this check box has no effect.
XML and XSL files
For the first option, Show table columns as ‘Elements’implies, all table columns
are generated as elements. Each element name follows the table column name.
In our example, the elements are <FLIGHT>, <NAME>, <MEMBERSHIP>,
<AIRCRAFT>, etc. The elements are part of the
<PASSENGER_SCHEDULE_AIRCRAFT> element, which is a derivation from the names
of the three tables. The <SQLResult> is the root element for all the options.
Example 6-1 XSL file for Show table columns as ‘Elements’
<?xml version="1.0" encoding="UTF-8"?>
<xsl:transform exclude-result-prefixes="sqltoxml" version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="html"/>
<xsl:template match="/">
<HTML>
<HEAD>
<META content="text/html; charset=iso-8859-1" http-equiv="Content-Type"/>
<META content="0" http-equiv="Expires"/>
</HEAD>
<BODY>
<DIV>
<xsl:apply-templates/>
</DIV>
</BODY>
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</HTML>
</xsl:template>
<xsl:template match="SQLResult">
<Table border="2">
<TR>
<TD>FLIGHT</TD>
<TD>NAME</TD>
<TD>MEMBERSHIP</TD>
<TD>AIRCRAFT</TD>
<TD>DEPARTURE</TD>
<TD>ARRIVAL</TD>
<TD>TYPE</TD>
</TR>
<xsl:for-each select="PASSENGER_SCHEDULE_AIRCRAFT">
<TR>
<TD>
<xsl:value-of select="FLIGHT"/>
</TD>
<TD>
<xsl:value-of select="NAME"/>
</TD>
<TD>
<xsl:value-of select="MEMBERSHIP"/>
</TD>
<TD>
<xsl:value-of select="AIRCRAFT"/>
</TD>
<TD>
<xsl:value-of select="DEPARTURE"/>
</TD>
<TD>
<xsl:value-of select="ARRIVAL"/>
</TD>
<TD>
<xsl:value-of select="TYPE"/>
</TD>
</TR>
</xsl:for-each>
</Table>
</xsl:template>
</xsl:transform>
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Figure 6-3 XML file generated with the Elements option
With the Attributes option all the column name are generated as attributes
(Figure 6-3). The attribute name takes on the name of the column. Similarly, all
the attributes are within the <PASSENGER_SCHEDULE_AIRCRAFT> element.
(Figure 6-4).
Figure 6-4 XML file generated with the Attributes option
When the‘Primary key as attributesoption is chosen, the XML file produced
has the flight and membership columns generated as attributes, and the
remaining columns as elements. The attribute with the foreign key aircraft still
comes out as an element. When the Foreign key as links option, this column
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tables still remains an element. However, with this same option, but with the
Recurse through foreign keys check box ticked, this column is generated as an
attribute. This option also generates a XSL and XML file for the AIRCRAFT table.
For the these files for the AIRCRAFT table, the primary key, aircraft_key, is
element is <SQLResult> and the <AIRCRAFT> element holding the attributes
and elements is names after the table.
HTML file
The resulting HTML files (Figure 6-5 and Figure 6-6) generated by the first three
options, (‘Elements’, ‘Attributes’ and ‘Primary keys as attributes’) produce similar
results. A HTML form is produced for all the fields selected.
Figure 6-5 HTML for ‘Elements’, ‘Attributes’, and ‘Primary key as attributes’
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Figure 6-7 HTML generated for Foreign key as links option
With the ‘Foreign key as links’ option, the HTML form generated adds a link for
every attribute which is a key (Figure 6-7). When the ‘Recurse though foreign
key’ check box is ticked, the ‘aircraft’ fields also gets an HREF attribute added to
the link. This link calls the AIRCRAFT HTML form as shown in Figure 6-8.
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Figure 6-8 Aircraft HTML generated for ‘Foreign key as links’ option
XML Schema file
The XML Schema and DTD files vary depending on the option chosen on the
Show table columns as.
The XML Schema file for the Elements option is shown below:
Example 6-2 XML Schema file for “Show table columns as ‘Elements’”
[001] <?xml version="1.0" encoding="UTF-8"?>
[002] <schema targetNamespace="http://www.ibm.com/PASSENGER_SCHEDULE_AIRCRAFT"
xmlns="http://www.w3.org/2001/XMLSchema"
xmlns:PASSENGER_SCHEDULE_AIRCRAFT="http://www.ibm.com/PASSENGER_SCHEDULE_AIRCRA
FT">
[003] <element name="SQLResult">
[004]
[005]
[006]
<complexType>
<sequence>
<element maxOccurs="unbounded" minOccurs="0"
ref="PASSENGER_SCHEDULE_AIRCRAFT:PASSENGER_SCHEDULE_AIRCRAFT"/>
[007]
[008]
</sequence>
</complexType>
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[009]
[010]
<key name="PASSENGER_SCHEDULE_AIRCRAFTPRIMKEY">
<selector
xpath="PASSENGER_SCHEDULE_AIRCRAFT:PASSENGER_SCHEDULE_AIRCRAFT"/>
[011]
[012]
[013]
<field xpath="PASSENGER_SCHEDULE_AIRCRAFT:FLIGHT"/>
<field xpath="PASSENGER_SCHEDULE_AIRCRAFT:MEMBERSHIP"/>
</key>
[014] </element>
[015] <element name="PASSENGER_SCHEDULE_AIRCRAFT">
[016]
[017]
[018]
[019]
[020]
[021]
[022]
[023]
[023]
[024]
[025]
<complexType>
<sequence>
<element ref="PASSENGER_SCHEDULE_AIRCRAFT:FLIGHT"/>
<element ref="PASSENGER_SCHEDULE_AIRCRAFT:NAME"/>
<element ref="PASSENGER_SCHEDULE_AIRCRAFT:MEMBERSHIP"/>
<element ref="PASSENGER_SCHEDULE_AIRCRAFT:AIRCRAFT"/>
<element ref="PASSENGER_SCHEDULE_AIRCRAFT:DEPARTURE"/>
<element ref="PASSENGER_SCHEDULE_AIRCRAFT:ARRIVAL"/>
<element ref="PASSENGER_SCHEDULE_AIRCRAFT:TYPE"/>
</sequence>
</complexType>
[026] </element>
[027] <element name="FLIGHT">
[028]
[029]
[030]
[031]
[032]
<simpleType>
<restriction base="string">
<maxLength value="30"/>
</restriction>
</simpleType>
[033] </element>
[034] <element name="NAME" nillable="true">
[035]
[036]
[037]
[038]
[039]
<simpleType>
<restriction base="string">
<maxLength value="20"/>
</restriction>
</simpleType>
[040] </element>
[041] <element name="MEMBERSHIP">
[042]
[043]
[044]
[045]
[046]
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
[047] </element>
[048] <element name="AIRCRAFT" nillable="true">
[049]
[040]
[051]
[052]
[053]
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
[054] </element>
[055] <element name="DEPARTURE" nillable="true">
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[056]
[057]
[058]
[059]
[060]
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
[061] </element>
[062] <element name="ARRIVAL" nillable="true">
[063]
[064]
[065]
[066]
[067]
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
[068] </element>
[069] <element name="TYPE" nillable="true">
[070]
[071]
[072]
[073]
[074]
<simpleType>
<restriction base="string">
<maxLength value="30"/>
</restriction>
</simpleType>
[075] </element>
[076]</schema>
The first element generated is SQLResult is the complex type. Appropriately, it
can have a minimum of no records with the upper-limit being unbounded. In the
‘key element the two attributes, ‘flight’ and ‘membership’, that make up the key
are declared within the ‘field’ element (line 11 and 12).
Every column name has been declared as an <simpleType> element, each of
type string and a max length (lines 27 to 75). This has been declared a
<restriction> element. All columns, besides ‘flight’ and ‘membership’ columns,
are declared as nillable.
The element <PASSENGER_SCHEDULE_AIRCRAFT> has been declared as a
complexType which hold all the other elements and to be in the order specified
(lines 16 to 25).
The XML Schema file generated through the ‘Attributes’ option is tabulated
below:
Example 6-3 XML Schema file for Show table columns as ‘Attributes’
[001]<?xml version="1.0" encoding="UTF-8"?>
[002]<schema targetNamespace="http://www.ibm.com/PASSENGER_SCHEDULE_AIRCRAFT"
xmlns="http://www.w3.org/2001/XMLSchema"
xmlns:PASSENGER_SCHEDULE_AIRCRAFT="http://www.ibm.com/PASSENGER_SCHEDULE_AIRCRA
FT">
[003]
[004]
<element name="SQLResult">
<complexType>
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[005]
[006]
<sequence>
<element maxOccurs="unbounded" minOccurs="0"
ref="PASSENGER_SCHEDULE_AIRCRAFT:PASSENGER_SCHEDULE_AIRCRAFT"/>
[007]
[008]
[009]
[010]
</sequence>
</complexType>
<key name="PASSENGER_SCHEDULE_AIRCRAFTPRIMKEY">
<selector
xpath="PASSENGER_SCHEDULE_AIRCRAFT:PASSENGER_SCHEDULE_AIRCRAFT"/>
[011]
[012]
[013]
[014]
[015]
[016]
[017]
[018]
[019]
[020]
[021]
[022]
[023]
[024]
[025]
[026]
[027]
[028]
[029]
[030]
[031]
[032]
[033]
[034]
[035]
[036]
[037]
[038]
[039]
[040]
[041]
[042]
[043]
[044]
[045]
[046]
[047]
[048]
[049]
[050]
[051]
<field xpath="@FLIGHT"/>
<field xpath="@MEMBERSHIP"/>
</key>
</element>
<element name="PASSENGER_SCHEDULE_AIRCRAFT">
<complexType>
<attribute name="FLIGHT">
<simpleType>
<restriction base="string">
<maxLength value="30"/>
</restriction>
</simpleType>
</attribute>
<attribute name="NAME">
<simpleType>
<restriction base="string">
<maxLength value="20"/>
</restriction>
</simpleType>
</attribute>
<attribute name="MEMBERSHIP">
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
</attribute>
<attribute name="AIRCRAFT">
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
</attribute>
<attribute name="DEPARTURE">
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
</attribute>
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[052]
[053]
[054]
[055]
[056]
[057]
[058]
[059]
[060]
[061]
[062]
[063]
[064]
[065]
[066]
[067]
<attribute name="ARRIVAL">
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
</attribute>
<attribute name="TYPE">
<simpleType>
<restriction base="string">
<maxLength value="30"/>
</restriction>
</simpleType>
</attribute>
</complexType>
</element>
[068]</schema>
In contrast to the previous example, every column name is now declared as an
attribute. The <restriction>element is still applied every column, but this time
all the attributes do not have the ‘nullable’ attribute set to true. All the attributes
are within a complexType element ‘PASSENGER_SCHEDULE_AIRCRAFT’.
Also, in the <key> element, this time, the field attributes are declared as
‘@FLIGHT and @MEMBERSHIP, (lines 11 and 12 in Example 5-3) as compared
to "PASSENGER_SCHEDULE_AIRCRAFT:FLIGHT" and
"PASSENGER_SCHEDULE_AIRCRAFT:MEMBERSHIP" (lines 11 and 12 in
Example 5-2).
Choosing option ‘Primary key as attributes’ will produce an XML Schema file
which is a combination of the previous two examples. The flight and membership
columns are generated as attributes, with the remaining fields produced as
elements. The element ‘PASSENGER_SCHEDULE_AIRCRAFT’ now holds a
complexType containing the elements with two attributes.
With the ‘Foreign Key as links’ option and the ‘Recurse through Foreign keys’
check box ticked, the AIRCRAFT column now becomes an attribute instead of an
element. With that it is removed as element from the complexType element
‘PASSENGER_SCHEDULE_AIRCRAFT’. Also an XML Schema file is also
produced for the AIRCRAFT table, which is produced here:
Example 6-4 XML Schema for AIRCRAFT table
<?xml version="1.0" encoding="UTF-8"?>
<schema targetNamespace="http://www.ibm.com/AIRCRAFT"
xmlns="http://www.w3.org/2001/XMLSchema"
xmlns:AIRCRAFT="http://www.ibm.com/AIRCRAFT">
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<element name="SQLResult">
<complexType>
<sequence>
<element maxOccurs="unbounded" minOccurs="0"
ref="AIRCRAFT:AIRCRAFT"/>
</sequence>
</complexType>
<key name="AIRCRAFTPRIMKEY">
<selector xpath="AIRCRAFT:AIRCRAFT"/>
<field xpath="@AIRCRAFT_KEY"/>
</key>
</element>
<element name="AIRCRAFT">
<complexType>
<sequence>
<element ref="AIRCRAFT:TYPE"/>
</sequence>
<attribute name="AIRCRAFT_KEY">
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
</attribute>
</complexType>
</element>
<element name="TYPE" nillable="true">
<simpleType>
<restriction base="string">
<maxLength value="30"/>
</restriction>
</simpleType>
</element>
</schema>
DTD file
The Schema definition can also be generated as a DTD. Here we will compare
the DTD generated by each of the options. With the Show table columns as
‘Elements’ option, the following DTD is generated:
Example 6-5 DTD generated by the Show table as ‘Elements’ option
<?xml version="1.0" encoding="UTF-8"?>
<!ELEMENT SQLResult (PASSENGER_SCHEDULE_AIRCRAFT)*>
<!ELEMENT PASSENGER_SCHEDULE_AIRCRAFT
(FLIGHT,NAME,MEMBERSHIP,AIRCRAFT,DEPARTURE,ARRIVAL,TYPE) >
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<!ELEMENT FLIGHT (#PCDATA)>
<!ELEMENT NAME (#PCDATA)>
<!ELEMENT MEMBERSHIP (#PCDATA)>
<!ELEMENT AIRCRAFT (#PCDATA)>
<!ELEMENT DEPARTURE (#PCDATA)>
<!ELEMENT ARRIVAL (#PCDATA)>
<!ELEMENT TYPE (#PCDATA)>
As expected, all column names have been generated as elements. Comparing
DTDs with XML Schemas, show how verbose and versatile XML Schemas can
be.
When the DTD is produced through the “Show table as ‘Attributes’” the column
names are produced as attributes.
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Example 6-6 DTD generated by the Show table as ‘Attributes’ option
<?xml version="1.0" encoding="UTF-8"?>
<!ELEMENT SQLResult (PASSENGER_SCHEDULE_AIRCRAFT)*>
<!ELEMENT PASSENGER_SCHEDULE_AIRCRAFT EMPTY>
<!ATTLIST PASSENGER_SCHEDULE_AIRCRAFT
FLIGHT CDATA #REQUIRED
NAME CDATA #REQUIRED
MEMBERSHIP CDATA #REQUIRED
AIRCRAFT CDATA #REQUIRED
DEPARTURE CDATA #REQUIRED
ARRIVAL CDATA #REQUIRED
TYPE CDATA #REQUIRED
>
When the ‘Primary keys as attributes’ option is selected, the ‘flight’ and
‘membership’ columns are generated as attributes, the remaining columns are
produced as elements.
With the ‘Foreign key as links’ option, the aircraft column is also generated as an
attribute. Additionally, an selectPassengerList_AIRCRAFT.dtd file is generated,
which is shown below:
Example 6-7 DTD for AIRCRAFT table with the Show tables as Foreign keys as links
<?xml version="1.0" encoding="UTF-8"?>
<!ELEMENT SQLResult (AIRCRAFT)*>
<!ELEMENT AIRCRAFT (TYPE) >
<!ATTLIST AIRCRAFT
AIRCRAFT_KEY ID #REQUIRED
>
<!ELEMENT TYPE (#PCDATA)>
The Query template file
To generate the Query template file, the user needs to tick the ‘Generate query
template file in the Save query box as can be seen in Figure 5-2.
Example 6-8 The Query template file for Passenger List select
<?xml version="1.0" encoding="UTF-8"?>
<SQLGENERATEINFORMATION>
<DATABASEINFORMATION>
<LOGINID>osamurs3</LOGINID>
<PASSWORD><![CDATA[osamurs3]]></PASSWORD>
<JDBCDRIVER>COM.ibm.db2.jdbc.app.DB2Driver</JDBCDRIVER>
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<JDBCSERVER>jdbc:db2:AIRLINE</JDBCSERVER>
</DATABASEINFORMATION>
<STATEMENT>
<![CDATA[ SELECT OSAMURS3.PASSENGER.FLIGHT,
OSAMURS3.PASSENGER.NAME,
OSAMURS3.PASSENGER.MEMBERSHIP,
OSAMURS3.SCHEDULE.AIRCRAFT,
OSAMURS3.SCHEDULE.DEPARTURE,
OSAMURS3.SCHEDULE.ARRIVAL,
OSAMURS3.AIRCRAFT.TYPE
FROM OSAMURS3.PASSENGER,
OSAMURS3.SCHEDULE,
OSAMURS3.AIRCRAFT
WHERE OSAMURS3.PASSENGER.FLIGHT =
OSAMURS3.SCHEDULE.FLIGHTNO
AND OSAMURS3.SCHEDULE.AIRCRAFT = OSAMURS3.AIRCRAFT.AIRCRAFT
ORDER BY FLIGHT, NAME ]]>
</STATEMENT>
<OPTIONS>
<FORMATOPTION>GENERATE_AS_ELEMENTS</FORMATOPTION>
<RECURSE>FALSE</RECURSE>
</OPTIONS>
</SQLGENERATEINFORMATION>
This file provides database connection information within the
<DATABASEINFORMATION> element and the SQL statement for the SQL
Query within <STATEMENT> element.
With any of the ‘Show table columns as’ options, the contents of the file do not
change except for the <FORMATOPTION> element. If the ‘Elements’ option is
chosen, this element is produced as shown in the example above. For the
‘Attributes’ option, the element has contents: ‘GENERATE_AS_ATTRIBUTES.
Similarly, it has ‘GENERATE_PRIMARYKEYS_AS_ATTRIBUTES’ for the ‘Primary Key as
attributes’ option. When the ‘Foreign keys as links’ option is selected, this
element has contents: ‘GENERATE_ID_AND_IDREF’ and depending if the ‘Recurse
through foreign keys’ is checked on not, the <RECURSE> element has a value set
to either ‘TRUE’ or ‘FALSE’.
The Query Template file can be used to execute SQL statements at runtime.
Application Developer comes with a SQLtoXML Java class library, which can be
used in an application or servlet to execute SQL statements and produce results
as XML. A example servlet, XMLIntegratorServerlet, has been provided, which
can be used as a sample for an application.
These references are available:
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6.2 The XML to SQL wizard
The XML to SQL wizard enables to insert or update the database record using
an XML. It works as the opposite way to SQL to XML wizard and this wizard is
available on Application Developer V5 above. Example 6-9 is showing the result
xml from SQL to XML wizard. This xml is representing a record of the customer
database and we will insert new record into the database.
Example 6-9 Customer.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE SQLResult SYSTEM "Customer.dtd">
<SQLResult>
<CUSTOMER>
<FIRSTNAME>Osamu</FIRSTNAME>
<LASTNAME>Takagiwa</LASTNAME>
<SERIAL>6287</SERIAL>
<EMAIL>[email protected]</EMAIL>
</CUSTOMER>
</SQLResult>
Go to the navigator view of the XML Perspective, then right-click on the
customer.xml or the XML, which is representing the customer record on your
workbench. Select Generate -> Database data and open the XML to SQL
wizard window (Figure 6-9). We already defined the connection to the airline
database, so we will reuse it by clicking the use existing connection box, then
click Next.
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Figure 6-9 XML to SQL wizard - Selecting the connection
The schema list is generated by the connection object and the table name is
Note: The XML to SQL always picks the second child element from the XML.
The action can be Insert or Update. We are going to insert the new record, so
select the Insert (Figure 6-10) then click Next.
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Figure 6-10 XML to SQL wizard: Selecting Schema and Action
Since the serial is a key, you cannot de-select it. The other columns, you can
de-select if you want (Figure 6-11). Then click Finish to insert. Using the update
action, you can update the record.
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Figure 6-11 XML to SQL wizard: Selecting the column
6.3 The DDL to XML Schema wizard
From a table definition, it is possible to generate an XML Schema. In the Data
perpective, from the Data Definition view, navigate to the table that you want to
the XML Schema from. Right-click on the table, and the pop-up menu should
present an option to Generate XML Schema (Figure 6-12).
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Figure 6-12 Generate XML Schema
The XML Schema generated for the SCHEDULE table is shown below:
Example 6-10 XML Generated through the DDL to XML Schema
<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.ibm.com/AIRLINE/OSAMURS3"
xmlns:AIRLINEOSAMURS3="http://www.ibm.com/AIRLINE/OSAMURS3">
<element name="SCHEDULE" type="AIRLINEOSAMURS3:SCHEDULE">
<key name="SCHEDULEPRIMKEY">
<selector xpath="AIRLINEOSAMURS3:SCHEDULE"/>
<field xpath="FLIGHTNO"/>
</key>
</element>
<complexType name="SCHEDULE">
<sequence>
<element name="FLIGHTNO">
<simpleType>
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<restriction base="string">
<length value="30"/>
</restriction>
</simpleType>
</element>
<element name="AIRCRAFT">
<simpleType>
<restriction base="string">
<length value="10"/>
</restriction>
</simpleType>
</element>
<element name="DEPARTURE">
<simpleType>
<restriction base="string">
<length value="10"/>
</restriction>
</simpleType>
</element>
<element name="ARRIVAL">
<simpleType>
<restriction base="string">
<length value="10"/>
</restriction>
</simpleType>
</element>
</sequence>
</complexType>
</schema>
For the tables that we have used in our example, the schemas generated are
quite simple. Here we generated a schema for the SCHEDULE table. The main
element is named as SCHEDULE after the table, and our key here is just the
flightNo. All the attributes within the table are held within a complexType element,
the attributes themselves have been generated as elements. Notice that a
<sequence> element has not been enforced on the order of the columns in the
XML Schema.
In this example, the foreign key from the Aircraft column to the AIRCRAFT table
has not been given any extra attention. It appears just like another column in the
table. When a XML Schema is generated for the AIRCRAFT table, the XML
Schema does not show any relationship with the SCHEDULE XML Schema.
An alternative to this method of generating a schema from a table would be to
use a select statement. Looking at Figure 5.1, showing the Passenger List
statement, one could create a select statement just on the SCHEDULE table.
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From there, using the XML from SQL wizard, the user has a few options on how
to create the XML Schema. The example below was created with the Show
tables as Primary keys as attributes:
Example 6-11 XML Schema for a single table using a Select
<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.ibm.com/SCHEDULE"
xmlns:SCHEDULE="http://www.ibm.com/SCHEDULE">
<element name="SQLResult">
<complexType>
<sequence>
<element maxOccurs="unbounded" minOccurs="0"
ref="SCHEDULE:SCHEDULE"/>
</sequence>
</complexType>
<key name="SCHEDULEPRIMKEY">
<selector xpath="SCHEDULE:SCHEDULE"/>
<field xpath="@FLIGHTNO"/>
</key>
</element>
<element name="SCHEDULE">
<complexType>
<sequence>
<element ref="SCHEDULE:AIRCRAFT"/>
<element ref="SCHEDULE:DEPARTURE"/>
<element ref="SCHEDULE:ARRIVAL"/>
</sequence>
<attribute name="FLIGHTNO">
<simpleType>
<restriction base="string">
<maxLength value="30"/>
</restriction>
</simpleType>
</attribute>
</complexType>
</element>
<element name="AIRCRAFT" nillable="true">
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
</element>
<element name="DEPARTURE" nillable="true">
<simpleType>
<restriction base="string">
<maxLength value="10"/>
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</restriction>
</simpleType>
</element>
<element name="ARRIVAL" nillable="true">
<simpleType>
<restriction base="string">
<maxLength value="10"/>
</restriction>
</simpleType>
</element>
</schema>
The main difference here is that the primary key is now generated as an attribute
and a sequence has been forced on the remaining columns and they can be set
to null.
6.4 DB2 XML Extender
This section has been adapted from Chapter 9 of the redbook DB2 e-business
Guide (SG2-6539).
There are different DB2 Extender products available to provide the functions to
support e-Business requirements that include support for different media types,
full text search capability, fast search capability to be used over the Internet, and
support for XML data. These are:
ꢀ
ꢀ
ꢀ
ꢀ
XML Extender
Text Extender
Net Search Extender
Audio Image Video (AIV) Extender
The basic idea behind all the DB2 extenders is that they provide the means to
support a new data type. That is, a table column can hold special type of data,
such as a text document. In order to support the new data type, the extenders
define user defined types, user defined functions, stored procedures, and a new
set of tables. The Extenders also exploit DB2's support for large objects of up to
2 gigabytes, and use DB2 triggers to provide integrity checking across database
tables ensuring the referential integrity of the data.
A User-Defined Type (UDT) is a way to create a new data type that has its own
semantics based on existing built-in types. For example, the XML Extender
creates the XMLCLOB UDT from the existing CLOB (character large object) data
type to support XML data in DB2. The CLOB data type is itself derived from the
LOB (large object) data type.
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A User-Defined Function, UDF, is a way to create functions that can be used
within an SQL statement, and thus add to the set of built-in SQL functions
supplied with DB2. For example, the XML Extender creates the
XMLCLOBFromFile UDF to insert XML data from a file into an XMLCLOB
column.
XML Extender
The XML Extender, extends the capability of DB2 to work with data in XML
documents. This means that you can store, update, and retrieve XML documents
from DB2 tables with the help of the XML Extender.
A summary of the facilities that the XML Extender provides:
ꢀ
ꢀ
Stores and retrieves as-is XML documents in DB2 table columns
Stores the elements and attributes of an XML document in separate tables, or
separates columns within the same table
ꢀ
Composes an XML document with data that is residing in existing DB2 tables.
The XML Extender performs a series of tasks in order to enable a DB2 database
and table for XML data. These tasks include:
ꢀ
ꢀ
Create a set of tables for its own use
Create User Defined Types (UDT) to accommodate XML data in table
ꢀ
ꢀ
Create Used Defined Functions (UDF) and stored procedures (SP) to
manipulate XML data
Create triggers to maintain the data integrity for the XML data spread across
multiple tables
Figure 6-13 shows an overview of the XML Extender.
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XML Extender Overview
Application
XML
DB2 XML Extender
Documents
Document compose,
decompose, update & delete
(UDFs and Stored
Document insert, update, delete,
search & retrieve
(UDFs and Stored Procedures)
Procedures)
DTD
(Document
Type
Definition)
XML Column
XML Collection
DTD_REF
User Tables
XML Side Tables
DAD
XML_USAGE
(Data
Access
Definition)
Traditional
Relational Tables
Figure 6-13 XML Extender overview
Administrative support tables, UDTs, and UDFs
The XML Extender creates the following set of administrative support tables
(Table 6-1), UDTs (Table 6-2), UDFs (Table 6-3) and stored procedures
(Table 6-4) when a database is enabled for XML.
Table 6-1 .Administrative support tables created
Table Name
XMLUsage
DTD_Ref
Description
Stores the Document Access Definition (DAD) files
Stores the DTDs used to vaildate XML documents
The schema qualifier for all the tables, UDFs and stored procedures created is
DB2XML.
Table 6-2 UDTs created
UDT
Description
XMLVarchar
Stores small XML documents with base type VARCHAR
(3000 bytes)
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UDT
Description
XMLCLOB
Stores large XML documents with the base type CLOB,
up to 2 GIG
XMLFile
References an external XML document file using the
base type VARCHAR(512)
This means that you will have to provide the qualifier for each reference to a
UDT, UDF, table or stored procedure created by the extender.
Table 6-3 UDFs created
UDF
Description
XMLVarcharFromFile
Import XML document from a file to a XMLVarchar
column
XMLCLOBFromFile
XMLFileFromVarchar()
XMLFileFromCLOB()
Content()
Import XML document from a file to a XMLCLOB
column
Import XML document from a XMLVarchar column to
XML file
Import XML document from a CLOB column to XML
file
Export XML document from XMLVarchar, XMLCLOB or
XMLFile
extract functions
Update()
For example, find an element/attribute within an
XML document that only has a single value
Replace XML document stored in XML columns by
changing some element or attribute value
For example, if you want to refer the data type XMLVarchar in a SQL statement,
you will refer it as DB2XML.XMLVarchar.
Table 6-4 Stored Procedures created
Stored Procedure
dxxEnableDB()
Description
Enable database for XML
dxxDisableDB()
Disable database for XML
dxxEnableColumn()
dxxDisableColumn()
dxxEnableCollection()
dxxDisableCollection()
Enable table column for XML data
Disable table column for XML data
Enables a collection of tables for XML
Disables an enabled collection
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Stored Procedure
Description
dxxGenXML()
uses a DAD file for an XML collection to compose XML
documents
dxx.RetrieveXML
dxxShredXML()
dxxInsertXML()
uses an XML enabled collection to compose XML
documents
uses a DAD file for an XML collection to decompose XML
documents
uses an XMLenabled collection to decompose XML
documents
DTD Repository
The DTD Repository is a table created by the XML Extender when a database is
enabled for XML. The table name is DTD_REF. Each row of this table represents
a DTD with additional metadata information. Users can access this table to insert
their own DTDs. The DTDs in this table are used when the validation of an XML
document is requested.
The DTD_REF table has the following columns:
ꢀ
DTDID: This column specifies the location of the DTD file that you will insert
into the DTD_REF table. For example, our DTD file ’redbook.DTD’ is located
in the directory x:\redbooks\SG246586\code\redbook.dtd, where x is the
local hard-disk drive letter.
ꢀ
CONTENT: This column contains the actual DTD file content. To insert data
into the XML enabled column of a table, (depending on the data type you
chose for the table column to store the XML data) the insert parameter will be:
db2xml.XMLClobFromFile(’x:\redbooks\SG246586\code\redbook.dtd’)
Here db2xml is the schema qualifier for the function XMLClobFromFile. The
full path to the dtd file, required by the function, is specified in parenthesis. We
assumed that if you chose XMLCLOB data type for the table column in which
you will store the XML data.
ꢀ
ꢀ
USAGE_COUNT: this column indicates the number of XML documents for
which this DTD is being used.
The column names AUTHOR, CREATOR, UPDATOR are self-explanatory.
The DTD_REF table is an administrative support table created by XML Extender
for its own use. The other administrative support table is the XML_USAGE table.
This table maintains the Document Access Definition (DAD) files. We will now
describe what a DAD file is and how it is used.
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Document Access Definitions (DAD)
The Document Access Definitions file, itself an XML formatted document, is used
to associate the XML document structure to a DB2 database. Basically, it
provides the mapping between the elements or attributes of an XML document
and the table columns, and the details of how a request for an XML document is
to be handled.
The DAD file answers questions like:
ꢀ
If the document is to stored in the database, then will it be stored as is, that is,
the complete document in a table column or not? If so, then do you need any
indexes built on the elements/attributes that are most frequently used as
search parameters?
ꢀ
ꢀ
Do you need to break up the elements/attributes of the xml document and
keep them in separate tables? If so, then which tables will participate in the
decomposition process?
Do you want to compose an xml document from data in DB2 tables? If so,
then the tables that will provide the elements/attributes and so on.
The structure of the DAD file depends on whether you are defining an XML
Column or Collection. For now, we will mention that the XML Column stores the
entire XML document as is, while the XML Collection takes the elements or
attributes from the XML document and stores them in separate tables or
columns.
The DAD file conforms to the DTD provided in the DAD.dtd file is located in the
dtd subdirectory of the XML Extender install directory. In the case of Windows NT
or Windows 2000, it is "<drive-letter>:\<installation
path>\dxx\dtd\DAD.dtd".
The XML Extender manages the DAD files with the administrative support table
XML_USAGE. This table is created when a database is enabled for XML. For
example, the DAD file that maps the element ’title’ from the DTD in Example 5-2
to a table column using the XML Column method is shown in Example 5-3:
Example 6-12 DTD representation of a book
<!ELEMENT redbook (title, subject, pubdate, leader, author*)>
<!ATTLIST redbook isbn ID CDATA #required>
<!ELEMENT title (#PCDATA)>
<!ELEMENT subject (#PCDATA)>
<!ELEMENT pubdate (#PCDATA)>
<!ELEMENT leader (#PCDATA)>
<!ELEMENT author (authorname, authorloc)>
<!ELEMENT authorname (#PCDATA)>
<!ELEMENT authorloc (#PCDATA)>
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Example 6-13 DAD file that maps the element ’title’ from the DTD
<Xcolumn>
<table name="redbook_title_sidetab">
<column name="title"
type="varchar(100)"
path="/redbook/title"
multi_occurence="NO"
</column>
</table>
</Xcolumn>
We can see the following tags in the DAD file shown in Example 5-3:
ꢀ <Xcolumn>, this tag indicates that we are using the XML Column method
ꢀ <table>, this tag identifies the side table that we want to create. A side table
is a table that is created if you want to index an element of the XML
document. In Example , we want to index the element ’title’ so that we can
later search for the XML document by title. The side table
redbook_title_sidetab will be created with a column called title, and will have
an index pointing to the exact location of the XML document in which the title
exists
ꢀ <column>, this tag specifies the columns that the side table will contain. The
number of column tags in the DAD file will depend on the elements or
attributes of the XML document that you want to index.
We also see that the column tag has four attributes:
– name: This attribute specifies the name of the column in the side table.
– path: This attribute indicates the location path in the XML document for
– type: This attribute indicates the data type of the table column that will be
used to store the element or attribute.
– multi-occurrence: This attribute indicates whether the element or attribute
referred to by the path attribute can occur more than once in the XML
document. In Example , the column tag ’title’ has multi-occurrence set to
"NO". This means that, the book will have only one title. All the column
tags that have multi-occurrence set to "NO" can be mapped to the table
columns within a single DB2 table.
If multi-occurrence is "YES" for a specific column tag, then there can be
only one column tag within that table tag. For each element or attribute
that has a multi-occurrence value of "YES", we need to declare a separate
a table with only one column that corresponds with this "multi-occurrence"
element/attribute (see “XML Column method” next).
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XML Column method
The XML Column method provides the facility to store the entire XML document
as is in a table column. The XML documents are inserted into table columns that
are enabled for XML and can be updated, retrieved, and searched. The XML
document can also be kept on the local file system and only a pointer to the
document be kept in the table column.
If you want to search the XML document based on certain element or attribute
values, you can map the element and attribute data from an XML document to
DB2 tables called side tables. We can build indexes on these side tables to
support fast structural search. Figure 5-6 gives an overview of the column
method.
When to use XML Column method
We recommend using the XML Column method under the following conditions:
ꢀ
ꢀ
The XML documents already exist.
There is a requirement to archive documents. For example, a news publishing
company that serves articles over the Web may want to maintain an archive
of published articles, which the users can search for.
ꢀ
ꢀ
ꢀ
ꢀ
Generally read-only documents
Stores documents externally, but use DB2 for management and search.
Requirement for range-based searches on document elements.
Documents with large text blocks (no larger than 2 GB, in which case the table
column cannot accommodate the document and it has to be decomposed into
more columns) which require structured searches using Text Extender.
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XML Column Method Overview
Application
DB2 XML Extender
XML
Documents
XML Column Method
Document insert, update, delete, search & retrieve
(UDFs and Stored Procedures
)
elements/attributes
"as is" xml document
DTD_REF
DTD
DAD
User Tables
XML Side Tables
xmlClob or
xmlVarchar
data-type
XML_USAGE
Figure 6-14 XML Column method overview
6.4.1 XML Collection
The XML Collection refers to a set of tables that is mapped to XML documents.
This method is used to decompose the incoming XML document into database
table columns or compose XML document from the data in database tables.
The XML Collection is defined in a DAD file, which specifies how the elements or
attributes of an XML document are mapped to one or more tables. The collection
is given a name so that it is easily run with stored procedures when composing or
decomposing the XML documents.
The tables can be a new set of tables that the XML Extender creates based on
the DAD file, when decomposing the XML document, or existing set of tables that
were used to compose the XML document. Columns of these tables are mapped
to the elements or attributes of the XML data. The data in these table columns
does not contain XML tags; it contains the content of the element and the values
of the attributes in the XML document. Figure 5-7 gives an overview of XML
collection.
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XML Collection Method Overview
Application
XML
Documents
DB2 XML Extender
XML Collection Method
Document compose, decompose, insertion,
update, delete, search & retrieval
elements/attributes
from xml document
decomposed into
table/columns
xml document
elements/attributes composed
from tables/columns
DTD_REF
DTD
DAD
XML_USAGE
(Data Access
Definition)
User tables
collection of tables enabled
for XML data
Figure 6-15 XML Collection Method overview
When to use XML Collection method
We recommend using the XML Collection method under the following conditions:
ꢀ
You have data in your existing DB2 database and you want to compose XML
documents based on a specified DTD. This is very helpful in exchanging data
between applications within an organization or across organizations so long
as the XML data conforms to the DTD.
ꢀ
ꢀ
You have XML documents that need to be stored with collections of data that
map well to relational tables.
You want to create different views of your relational data using different
mapping schemes. Basically, you can use the data in your database to
compose different XML documents based on your DTDs.
ꢀ
You have XML documents that from other data sources. You are interested in
the data but not the tags, and want to store pure data in your database. You
want the flexibility to store the XML data in existing tables or in new tables.
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Mapping schemes for XML collections
For using the XML collection method, you must select a mapping scheme that
defines how XML data is represented in a relational database.
For example, let us consider the DTD shown in Example 6-14.
Example 6-14 Sample DTD
<!ELEMENT employee (name, dept, proj*)>
<!ATTLIST employee empno CDATA #REQUIRED>
<!ELEMENT name (firstname, lastname)>
<!ELEMENT firstname (#PCDATA)>
<!ELEMENT lastname (#PCDATA)>
<!ELEMENT dept (#PCDATA)>
<!ELEMENT projno (#PCDATA)>
<!ELEMENT startdate (#PCDATA)>
For the sample DTD shown in Example 6-14, we can determine how we want to
create the tables (for decomposition) to map to the incoming XML document to
table columns. Figure 6-16 shows an example of the mapping scheme.
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root_node
element_node
Employee
element_node
Proj
element_node
dept
attribute_node
EmpNo
text_node
EMPNO
WORKDEPT
element_node
ProjNo
element_node
StartDate
text_node
text_node
PROJNO
EMSTDATE
element_node
Name
Names of columns in DB2 tables:
for example, EMPNO is a column in EMPLOYEE
table in SAMPLE database
element_node
firstName
element_node
lastName
text_node
text_node
FIRSTNAME
LASTNAME
Figure 6-16 XML Collection mapping scheme
By analyzing the mapping scheme we will be able to determine whether we can
compose the entire XML document with one SQL statement or not. You can use
one of the two types of mapping schemes when defining a collection in the DAD
file:
ꢀ SQL mapping. SQL mapping uses SQL SELECT statement to define the DB2
tables and conditions used for composing a document from the collection.
ꢀ RDB_node mapping. RDB_node mapping uses an XPath-based relational
database node (RDB_node). The RDB_node has child elements that define
the tables, columns, and conditions used to associate XML data with DB2
tables.
SQL mapping
Defining a DAD file with SQL mapping scheme allows direct mapping from
relational data to XML documents through a single SQL statement and the XPath
data model. When working with SQL mapping it is important to understand the
following points:
ꢀ
SQL mapping scheme can be used for composition, not for decomposition.
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ꢀ
ꢀ
ꢀ
The tag <SQL_stmt> identifies the SQL_stmt element in the DAD file.
The content of the element <SQL_stmt> is a valid SQL SELECT statement.
The SQL_stmt maps the columns in the SELECT statement to XML
document elements or attributes.
ꢀ
The column names in the SELECT define the value of an attribute_node or
the content of a text_node.
An attribute_node maps the value of an attribute in the XML document to a
table column.
A text_node maps the content of the element in the XML document to a table
column. A text_node is specified for the lowest level element nodes, that is,
these element nodes do not have any child elements.
ꢀ
ꢀ
The FROM clause of the SELECT identifies the tables containing the data.
The WHERE clause specifies join (the columns on which the collection tables
will be joined) and search condition.
Table 6-5 EMPLOYEE table in SAMPLE database
Column name
EMPNO
Data type
CHAR(6) NOT NULL
VARCHAR(12) NOT NULL
MIDINIT(1) NOT NULL
VARCHAR(15) NOT NULL
CHAR(3)
FIRSTNME
MIDINIT
LASTNAME
WORKDEPT
PHONENO
HIREDATE
JOB
CHAR(4)
DATE
CHAR(8)
EDLEVEL
SEX
SMALLINT NOT NULL
CHAR(1)
BIRTHDATE
SALARY
DATE
DECIMAL(9,2)
DECIMAL(9,2)
DECIMAL(9,2)
BONUS
COMM
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Table 6-6 EMP_ACT TABLE in SAMPLE database
Column name
EMPNO
Data type
CHAR(6) NOT NULL
CHAR(6) NOT NULL
DATE
PROJNO
EMSTDATE
Example 6-15 Example DAD file specification with SQL_mapping scheme
<?xml version="1.0"?>
<!DOCTYPE DAD SYSTEM "X:\dxx\dtd\dad.dtd">
<DAD>
<validation>NO</validation>
<SQL_stmt>
SELECT a.empno, firstname, lastname, workdept, b.projno, b.emstdate
from EMPLOYEE a, EMP_ACT b
where a.empno = b.empno order by b.projno
</SQL_stmt>
<prolog>?xml version="1.0"?</prolog>
<doctype>!DOCTYPE employee SYSTEM
"<drive-letter>:\redbooks\SG246586\code\employee.dtd">
</doctype>
<root_node>
<element_node name ="employee">
<attribute_node name="id">
<column name="empno"/>
</attribute_node>
<element_node name ="firstname">
<text_node>
<column name="firstname"/>
</text_node>
</element_node>
<element_node name ="lastname">
<text_node>
<column name="lastname"/>
</text_node>
</element_node>
<element_node name ="workdept">
<text_node>
<column name="workdept"/>
</text_node>
</element_node>
<element_node name ="project" multi_occurrence="YES">
<element_node name="projno">
<text_node>
<column name="projno>/>
</text_node>
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</element_node>
<element_node name ="startdate">
<text_node>
<column name="emstdate"/>
</text_node>
</element_node>
</element_node>
</element_node>
</root_node>
</Xcollection>
</DAD>
RDB_node mapping
This method defines the location of the content of an XML element or the value of
an attribute so that the XML Extender can determine where to store or retrieve
the XML data. It uses the XML Extender-provided RDB_node, which contains
one or more definitions for tables, optional columns, and conditions.
When working with RDB_node mapping it is important to understand the
following points ( Example 5.6 and 5.7 refer to Tabes 5.5 and 5.6):
ꢀ
decomposition.
ꢀ
Use <RDB_node> element in each of the top nodes for element_node and for
each attribute_node and text_node. An element_node corresponds to an
element in the XML document. An element_node can have child element
nodes. Refer SQL mapping for definition of attribute_node and text_node.
The top element_node in the DAD file identifies the root element of the
XML document. Specify an RDB_node as follows:
•
Specify all tables that are associated with the XML document. For the
mapping scheme shown in Figure 5-8, the RDB_node for the element
employee is shown in Example 6-16.
Example 6-16 The RDB_node
<element_node name="employee">
<RDB_node>
<table name="employee"/>
<table name="emp_act"/>
<condition>
employee.empno = emp_act.empno
/condition>
</RDB_node>
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•
•
For decomposing or enabling an XML collection specified in the DAD
file, you must specify a primary key for each table.
Use the orderBy attribute to recompose XML documents containing
elements or attributes with multiple occurrence.
– RDB_node for each attribute and text_node
Specify an RDB_node for each attribute_node and text_node, telling the
get data:
i. Specify the name of the table containing the column data. The table
name must be included in the RDB_node of the top element_node. In
Figure 5-8, the text_node of element <startdate> is associated with the
table emp_act. The RDB_node mapping is shown in Example 6-17.
Example 6-17 RDB_node mapping
<element_node name="startdate">
<text_node>
<RDB_node>
<table name="emp_act"/>
<column name="emstdate"/>
<condition>
emstdate > 2001-01-01
/condition>
</RDB_node>
</element_node>
ii. Specify the name of the table column that contains the data for the
element. In Example i, we specified the column EMSTDATE.
iii. Specify the condition under which the XML data is generated. In
Example i, we specified the condition for generating the XML data for
projects with project start date greater than ’2001-01-01’.
iv. For decomposing a document or enabling the XML collection specified
in the DAD file, you must specify the column type for each
attribute_node and text_node. For example, we can specify that the
column type for EMPNO is CHAR as follows:
<column name=”empno” type=char”>
XML Extender administration tools
The XML Extender administration functions help you to enable your database
and table columns for XML, and map XML data to DB2 relational structures. XML
Extender provides the following tools to complete administration tasks:
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1. A command line tool. The administration command is dxxadmand all the
administration functions can be executed with this command from the DB2
command window. For example, you can enter the following command in the
DB2 command window to enable a database for XML:
dxxadm enable_db databasename
2. An administration wizard. The wizard is a GUI tool that helps you accomplish
the administration such as, enabling a database, table, or column, enabling a
collection, or editing the DAD file. All the administration functions that you can
perform with the wizard are also available with the command line tool.
The functions to edit the DAD file are now available in the WebSphere Studio
Application Developer tool.
3. Programming interfaces. The XML Extender provides a number of UDFs that
can be used within the SQL statements, and stored procedures that can be
procedures is provided in “Administrative support tables, UDTs, and UDFs”
on page 128.
XML MQSeries enablement
In XML Column method, and XML Collection, we discussed the two methods of
storing and accessing XML data: the XML column method for storing/retrieving
as-is documents in the database tables, and the XML collection method for
decomposing incoming XML document into tables and composing XML
document from the data in DB2 tables.
With the MQ XML UDFs you can complete the following tasks:
ꢀ
ꢀ
ꢀ
Query XML documents with the XML column method, and then publish the
results to a message queue.
Retrieve an XML document from a message queue, decompose it into
untagged data and store the data in tables.
Compose an XML document from DB2 data and send the document to a
message queue.
MQSeries supports three messaging models:
ꢀ datagrams: Messages are sent to a single destination with no reply expected.
ꢀ publish/subscribe: Publishers and subscribers register with a publication
service. One or more publishers send a message to the publication service
which distributes the message to subscribers who want to receive the
message from the publisher.
ꢀ request/reply: Messages are sent to a single destination and the sender
expects a reply.
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You can use these three messaging models to distribute XML data and
documents between disparate applications with the help of MQSeries and
MQXML functions and stored procedures.
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7
Generators
In this chapter we discuss WebSphere Studio XML generators. With these tools
you can generate XML Schemas, XML from other components, and also
generate components from XML files and XML Schemas.
In this chapter describes the following generators:
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Schemas: DTD <—> XSD
XML: XML <—> DTD/XSD
XSD —> HTML doc
JavaBeans from DTD/XSD
JavaBeans —>XML/XSL
HTML —>XML/XSL
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7.1 DTD <—> XSD
WebSphere Studio Application Developer offers the developer the ability to
transform your XSD file to a DTD file or a DTD file to a XSD file, so whether you
start is a matter of in which schema you feel more comfortable. We are going to
use the DTD file shown in Figure 7-1.
Figure 7-1 passengerList.dtd
Having the passengerList.dtd file, we can generate the corresponding XSD file
using the generator following the next steps:
1. Select passengerList.dtd
2. Right-click Generate—>XML Schema
3. Select the folder to store the file. In this example it is Generators.
4. Click Finish.
The resulting XSD file is shown in Figure 7-2 on page 147.
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Figure 7-2 passengerList.xsd
7.2 XML <—> DTD/XSD
There are several ways to create XML files using Application Developer. Now we
are going to discuss how to:
ꢀ
ꢀ
ꢀ
ꢀ
Create an XML file from DTD file
Create an XML file form XSD file
Create a DTD file from an XML file
Create XSD from an XML file
This options are very convenient if you have an existing rules file that details how
the new XML file should look. By letting the XML file be created based on these
rules, you automatically get a coded skeleton for the file. The option to create
XML files from these file types is also available from the context menu of DTD
and XML Schema files. XML files are placed in an existing folder under any
project type. If you plan to create JavaBeans from your DTD files then this should
be a Java project.
7.2.1 Create an XML file from a DTD file
There are two ways to create an XML file from a DTD file. The first one is using
the Create XML File wizard:
1. Open XML perspective if necessary.
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2. Click File—>New—XML.
3. Select Create XML file from a DTD file.
4. Enter the folder to store the file. In this example is Generators.
5. Enter the XML file name. i.e. passengerList.xml. Click Next.
6. Click Select file from Workspace option.
7. From Workbench Files box, select passengerList.dtd. Click Next.
8. Select flight as root name.
9. Select Create required and optional content. Click Finish.
Figure 7-3 passengerList.xml
The second way to do it is using the context menu of the passengerList.dtd file:
1. Select passengerList.dtd.
2. Right-click Generate—>XML File
3. Enter the folder to store the file.
4. Enter passengerList.xml as file name. Click Next.
5. Select Flight as root element.
6. Select Create required and optional content. Click Finish.
7.2.2 Create an XML file from an XSD file
There are two ways to create an XML file from a XSD file. The first one is using
the Create XML File wizard: (See Figure 7-4.)
1. Open XML perspective if necessary.
2. Click File—>New—XML.
3. Select Create XML file from a XSD file.
4. Enter the folder to store the file. In this example it is Generators.
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5. Enter the XML file name. i.e. passengerList.xml. Click Next.
6. Select Select file from Workspace option.
7. From Workbench Files box, select passengerList.xsd. Click Next.
8. Select Flight as the root name.
9. Select Create required and optional content. Click Finish.
Figure 7-4 passengerList.xml
The second way to do it is using the context menu of the passengerList.xsd file:
1. Select passengerList.xsd.
2. Right-click Generate—>XML File
3. Enter the folder to store the file.
4. Enter passengerList.xmlas file name. Click Next.
5. Select Flight as root element.
6. Select Create required and optional content. Click Finish.
7.2.3 Create DTD/XSD files from XML
Now, let us work in the case that we have an XML file, and we need to create an
schema for it. Application Developer provides two wizards to generate the
schema from the XML file. To show you how to do this, we are going to use the
file Customer.xml which contains the personal data of a customer.
Example 7-1 Customer.xml
<?xml version="1.0" encoding="UTF-8"?>
<Root>
<Customer>
<Firstname>John</Firstname>
<Lastname>Doe</Lastname>
<Email>[email protected]</Email>
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<Membership>123456</Membership>
</Customer>
</Root>
To generate the DTD file follow the steps below:
1. Select customer.xml
2. Right-click Generate—>DTD
3. Enter the folder name to store the file.
4. Enter the file name. Click Finish.
See resulting DTD file below.
Example 7-2 Customer DTD
<?xml version='1.0' encoding="UTF-8"?>
<!ELEMENT Customer
(Firstname,Lastname,Email,Membership)
>
<!ELEMENT Email
(#PCDATA)
>
<!ELEMENT Firstname
(#PCDATA)
>
<!ELEMENT Lastname
(#PCDATA)
>
<!ELEMENT Membership
(#PCDATA)
>
<!ELEMENT Root
(Customer+)
>
1. Select Customer.xml.
2. Right-click Generate—>XML Schema.
3. Enter the folder to store the file.
4. Enter the file name. Click Finish.
See resulting XSD file in Example 7-3.
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Example 7-3 Customer.xsd
<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<xsd:element name="Customer">
<xsd:complexType>
<xsd:sequence>
<xsd:element ref="Firstname"/>
<xsd:element ref="Lastname"/>
<xsd:element ref="Email"/>
<xsd:element ref="Membership"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
<xsd:element name="Email" type="xsd:string"/>
<xsd:element name="Firstname" type="xsd:string"/>
<xsd:element name="Lastname" type="xsd:string"/>
<xsd:element name="Membership" type="xsd:string"/>
<xsd:element name="Root">
<xsd:complexType>
<xsd:sequence>
<xsd:element maxOccurs="unbounded" minOccurs="1"
ref="Customer"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:schema>
7.3 Generate a HTML from an XSD
We can generate a HTML document to describe how the XSD file is designed.
This document is similar to make a Java doc when creating documentation of
1. Select passengerList.xsd file.
2. Right-click Generate—>HTML Doc.
3. Enter the folder to store the documentation.
4. Enter the HTML file name. Click Finish.
Figure 7-5 is showing the result of this process.
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Figure 7-5 HTML Documentation for passengerList.xsd
7.4 JavaBeans from DTD/XSD
WebSphere Studio Application Developer gives us several tools to quickly build
applications. One of the tools is the generation of JavaBeans from an XML
Schema or a DTD file, which allows you to code directly to instance rather than
DOM APIs. This wizard:
ꢀ
ꢀ
ꢀ
Creates a bean for each element in DTD, XSD.
Creates a Factory bean for creation of a new XML document.
Creates a sample program for using the beans created.
To create the JavaBeans you need to have a container within Application
Developer. This must be a project which could contain Java classes such as Web
Project. To create a Web Project follow the next steps:
1. Click File—>New—>Project.
2. Select Web Project from Web category. Click Next.
3. Enter a project name, for example Travel.
4. Select J2EE Web Application Project. Click Next.
5. Create or select an Enterprise Application Project. Click Finish.
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To generate the JavaBeans from the schema follow the next steps:
1. Select passengerList.xsd.
3. Enter the container created before.
4. Enter a name for the package.
5. Select Flight as the root element.
6. Select Generate sample test program. Click Finish.
Figure 7-6 is showing the generated Java codes.
Figure 7-6 JavaBeans from schema
Take a few minutes to review the generated code, you will notice that some
classes extend ComplexType corresponding to main elements, and the other
classes extend SimpleType corresponding to sub elements. Try to run the
sample application to follow how it builds the XML file.
7.5 Generate XML/XSL from JavaBeans
You can generate Web pages that can access JavaBeans using XSL. For this
section we are going to use the JavaBean showed in Example 7-4. We create
this Java file in our Travel Web Project and the package is airline.
Example 7-4 passenger.java
package airline;
/**
* @author osamurs2
*
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* To change this generated comment edit the template variable "typecomment":
* Window>Preferences>Java>Templates.
*/
public class passenger {
private String name;
private String membership;
public passenger()
{
}
public String getName()
{
return name;
}
public void setName(String aName)
{
name=aName;
}
public String getMembership()
{
return membership;
}
public void setMembership(String aMem)
{
membership=aMem;
}
}
Several files are created in this generator:
ꢀ
ꢀ
Input XML Form: An XSL Stylesheet to render the JavaBean.
Result XSL: ResultXSL Stylesheet that displays results from the underlying
JavaBean.
ꢀ
ꢀ
ꢀ
ꢀ
Splash screen: A splash screen to invoke the XSLServlet.
XSLServlet: This servlet applies the generated XSL to the DOM.
XML DOM: Produces a DOM from the JavaBean.
XML Schema: Produces an XML Schema from the JavaBean.
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To generate all the files follow the steps below:
1. Open XML perspective if necessary.
2. Click File—>New—>Java Bean XML Client.
3. Enter your Web project created before as the destination folder.
4. Enter the package name for the Java files. Click Next.
5. Browse for the airline.passenger bean.
6. Select name and membership as the beans you would like to invoke. Click
Next.
7. Design Input form as desired. Click Next.
8. Design Result page as desired. Click Next.
9. Enter a prefix to the file names. Click Finish.
The generated servlet implements doGet method. This method returns the input
form that we designed before. To test the application, you need to call
PassengerXSLServlet directly from the URL (Figure 7-7).
Figure 7-7 Input XML Form screen
Click Submit to call the servlet’s doPost method (Figure 7-8).
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Figure 7-8 Result XSL panel
7.6 Generate XML/XSL from HTML
With this generator we are trying to create XSL and XML files from a specific
HTML, also will enable to separate out the presentation logic from the dynamic
presentation data into two XSL files. Once the separation is completed, you can
use XSLT technology to combine new data that is defined in XML format with the
generated XSL files to create new HTML Web pages.
So the first step will be to create a HTML file with data. We are going to create an
HTML for a customer information design as shown in Figure 7-9:
1. Click File—>New—>Other.
2. Select HTML from Web category.
3. Enter folder name. Enter Customer.htmlas file name.
4. Click Finish.
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Figure 7-9 Customer.html
7.6.1 Preparing the HTML file for generation
There are several steps to get the HTML file ready to generate XSL and XML file.
The first step is to rename customer.html to customero.xhtml, since the generator
is only available to files with this extension.
Open the renamed file and follow the next steps:
1. Delete any DOCTYPE declaration.
2. Remove any entity references. For example, substitute &nbsol with a blank.
3. Fix up any missing tags. For example, change <br>to </br>.
Adding annotation tags
The second step is to create a template file that contains the annotation tags, to
mark the section that contains data that needs to be extracted into the XML
document. To do this follow the next steps:
1. Copy customer.xhtml into a new file, for example, cus-template.xhtml.
2. Open cus_template.xhtml file and add the tag <?HTMLTemplate
version=”0.1”?> at the top to indicate that it is a template file.
3. Add the tag <TemplateRegion name=”nodeName”>around the data that you
want to convert.The nodeName name will be the node name in the resulting
XML file.
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4. Delete the repeating data in each TemplateRegion. In our example, we have
to delete the repeating records of customers to keep only one. (See
Example 7-5.)
5. Parameterized each data item using this format: {tagName}. The tagName
will be used in the resulting XML and XSL files.
Example 7-5 cus-template.xhtml
<?HTMLTemplate version="0.1"?>
<TemplateRegion name="Root">
<HTML>
<HEAD>
<META name="Generator" content="IBM WebSphere Studio"/>
<META http-equiv="Content-Style-Type" content="text/css"/>
<LINK href="/Travel/theme/Master.css" rel="stylesheet" type="text/css"/>
<TITLE>Customer.html</TITLE>
</HEAD>
<BODY>
<DIV align="center">
<TABLE border="1" width="524">
<TBODY>
<TR>
<TD width="133">
<FONT color="#000000" size="3" face="Times New Roman">
<B>Firstname</B></FONT></TD>
<TD width="123">
<FONT color="#000000" size="3" face="Times New Roman">
<B>Lastname</B></FONT></TD>
<TD width="123">
<FONT color="#000000" size="3" face="Times New Roman">
<B>Email</B></FONT></TD>
<TD width="133">
<FONT color="#000000" size="3" face="Times New Roman">
<B>Membership</B></FONT></TD>
</TR>
<TemplateRegion name="Customer">
<TR>
<TD width="133">
<FONT color="#000000" size="2" face="Times New Roman">
{Firstname}
</FONT>
</TD>
<TD width="123">
<FONT color="#000000" size="2" face="Times New Roman">
{Lastname}
</FONT>
</TD>
<TD width="123">
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<FONT color="#000000" size="2" face="Times New Roman">
{Email}
</FONT>
</TD>
<TD width="133">
<FONT color="#000000" size="2" face="Times New Roman">
{Membership}
</FONT>
</TD>
</TR>
</TemplateRegion>
</TBODY>
</TABLE>
</DIV>
</BODY>
</HTML>
</TemplateRegion>
The final step is to invoke the Generator. This wizard is going to generate the
XSL stylesheets, and optionally the XML data that can be extracted from your
HTML document:
1. Select cus-template.xhtml.
2. Right-click Generate—>XSL File.
4. Check Extract XML Data from HTML file.
5. Select Customer.xhtml. Click Next.
6. Enter the resulting XML filename, customer.xml, and select the folder to store
it. Click Finish.
Example 7-6 shows the generated xml.
Example 7-6 Customer.xml
<?xml version="1.0" encoding="UTF-8"?>
<Root>
<Customer>
<Firstname>Firstname</Firstname>
<Lastname>Lastname</Lastname>
<Email>Email</Email>
<Membership>Membership</Membership>
</Customer>
<Customer>
<Firstname>John</Firstname>
<Lastname>Doe</Lastname>
<Email>[email protected]</Email>
<Membership>123456</Membership>
</Customer>
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<Customer>
<Firstname>Liza</Firstname>
<Lastname>Stevens</Lastname>
<Email>[email protected]</Email>
<Membership>654321</Membership>
</Customer>
</Root>
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Part 3
XML application
development
Part three provides an overview of Web Services and Enterprise JavaBeans
capabilities of Application Developer. Then introduces how to create three type
of applications step-by-step.
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8
WebSphere and XML
approaches
Chapter eight provides an overview of Web services and Enterprise JavaBeans
capabilities of Application Developer. The overviews are a precursor to two
applications that have been detailed in Chapter 9, “Developing XML Web
services” on page 177 and Chapter 10, “Development of XML-based Enterprise
applications” on page 215.
The first, the Passenger List application demonstrates Application Developer’s
capabilities in creating and generating the basics in Data Access and XML files.
For the user interface, it uses HTML, XSLT stylesheets, servlets and XSL
transformers.The Customer Registration application is oriented towards the
usage of Enterprise JavaBeans.
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8.1 XML in Application development
Web services are becoming part of today’s Internet. They play a key role for
maximum interoperability across the different technologies on the Internet. XML’s
role is that of a data interchange format between the different components, not
only between applications, but also within the applications. In Client/Server and
distributed computing technologies, integration between proprietary systems was
always expensive and time-consuming. To derive efficiencies, systems had to be
tightly coupled and were not necessary kept to open-standards as we have now.
As compared to the binary formats used in those systems, XML is very verbose.
However, with the latest improvements in network technologies, especially in
network bandwidth, compression techniques and improvements in processing,
this disadvantage has been absolved.
In Web services, the data types are specified using XML Schema, which are an
improvements on DTDs, and the data that is exchanged is in XML format. In
other technologies, the proprietary systems had to make use of data structures
that were closely dependent on the underlying systems. An example, would be
an applications with its client running in Windows and the data being on a
mainframe systems. Data from the mainframe, being in EMBDIC format had to
be translated to formats suitable for the PC environment. If only, all data were in a
common format, that was shared by every system, data interchange issues
would have taken less of a priority.
As the usage of XML increases, tools and utilities will be required for authoring
XML, Schemas and the Web Services Description Language (WSDL). with these
new tools, application designers and developers will use XSD to gain flexibility in
their product and application implementations. Web services can now be
implemented using languages such as Java and Javascript. With XSLT, XML
Query language and the support for XML by major database vendors like IBM’s
DB2 UDB, XML documents are can be processed as they are, instead of having
to be converted between XML and other languages or formats. DB2 UDB
includes the XML Extender, which allows XML documents to be stored in
columns and also to be store the elements into tables as fields. The XML
Document Access Definition (DAD) files maps XML to relational data. Application
Studio has incorporated the RDB to XML mapper tool to facilitates the generation
of the DAD. From the DAD, the DB2 XML Extender (DADX) can be produced.
This file is in XML and contains operations defined by normal SQL statements
and calls to the stored procedures in the DB2 XML Extender. IBM SOAP includes
provides the handling of DADX files. This file, since it is ASCII text, can be easily
edited using any text editor or the XML editor tools.
Any distributed computing technology, they must be support for converting
between from one system to another. In the case of SOAP, the data interchange
format is XML and the run-time components are implemented in Java. Therefore,
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there a mapping between Java and XML data types must be provided for. The
Apache SOAP run-time environment allows the developer to map between Java
and XML data types for an encoding style. The designer can specify a serializer
to marshal the Java type to XML, a deserializer to unmarshall the XML type to
Java, or both for two-way mapping.
The rules for mapping between Java and XML data types are stored in a SOAP
mapping registry object that is used by either the Java client proxy or the Web
service. The SOAP mapping registry has predefined rules for mapping between
simple Java and XML types. For complex XML types, it is up to the developer to
specify the mapping. The best way to map is to use the org.w3c.dom.Element.
This represents a generic XML element in the Document Object Model (DOM).
8.2 Web services
A Web service is a collection of functions that are packaged as a single entity
and published to the network for use by other programs. Web services are
building blocks for creating open distributed systems, and allow companies and
individuals to quickly and cheaply make their digital assets available worldwide.
Some examples of Web services are:
ꢀ
ꢀ
ꢀ
A credit checking service that returns credit information when given a
person’s identification number.
A stock quote service that returns the sock price associated with a specified
ticker symbol.
A purchasing service that allows computer systems to buy office supplies
when given an item code and a quantity.
A Web service can aggregate other Web services to provide a higher-level set of
features. For example, a Web service could provide a set of high-level features by
orchestrating lower-level Web services for car rental, air travel, and hotels.
Applications of the future will be built from Web services that are dynamically
selected at runtime based on their cost, quality, and availability.
Web services are pretty much guaranteed to be at the heart of the next
generation of distributed systems. The reasons are:
ꢀ
Interoperability: Any Web service can interact with any other Web Service.The
Simple Object Access Protocol (SOAP), the new standard protocol by all of
the major vendors (and most of the minor ones), the agonies of converting
between CORBA, DCOM and other protocols should be over. And because
Web services can be written un any language, developers do not need to
change their developed environments in order to produce or consume Web
services.
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ꢀ
Ubiquity: Web Servies communicate using HTTP and XML. Therefore, any
device, which supports these technologies can both host and access Web
services. Pretty soon, they will be present in phones, cars, and even soda
machines. Soda supplies getting low? No problem, the wireless-networked
soda machine can contact their local supplier’s Web service and order more
of your favorite beverage.
ꢀ
ꢀ
Low barrier to Entry: The concept behind Web services are easy to
understand and free toolkits from vendors like IBM and Microsoft allow
developers to quickly create and deploy Web services. In addition, some of
the toolkits allow pre-existing COM components and JavaBeans to be easily
exposed as Web services.
Industry Support: All of the major vendors are supporting SOAP and the
surrounding Web services technology. For example, the Microsoft.NET
platform is based on Web services, thereby making it very easy for
components written in Visual Basic to be deployed as Web services, and
consumed by Web services written using WSAD and, and vice-versa.
Web Services Description Language (WSDL) is a new specification to describe
networked XML-based services. It provides a simple way for service providers to
describe the basic format of requests to their systems regardless of the
underlying protocol, such as SOAP and XML, or encoding, such as Multipurpose
Internet Messaging Extensions (MIME). WSDL is a key part of the effort of the
Universal Description, Discovery and Integration (UDDI) initiative to provide
directories and descriptions of such on-line services for electronic business.
Detail information is available:
The Web services (r)evolution: Applying Web services to applications by Graham
Glass at:
Using WSDL in SOAP applications: An introduction to WSDL for SOAP
programmers by Uche Oqbuji at:
8.3 Passenger List application
The Passenger List application was developed to demonstrate application
developer’s capabilities in a development environment. It consists of only a single
operation, that is, for a given flight number, the application retrieves a list of
passengers for that flight. All details of the passengers and schedules are stored
in the database. As in any such system, we hold flight details such flight
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numbers, aircraft types and arrival and departure times and also passenger
details names, membership number and the flight to be taken.
The database has been kept simple. We could have used other more complex
Application Studio.
8.3.1 Solution Outline
As in all applications, we are a clear distinction between the Graphical User
Interface, the Web Tier and the Data Source(Figure 8-1). The advantages of
these delineation are obvious. If the tier were loosely coupled, they could be
reused to interface with other components of different applications. The Client
interface could easily have been implemented using JSP, ASP or even
Javascript. Although we have generated HTML, we could easily have generated
a display for a PDA or a mobile phone, just but changing the XSL stylesheet.
Similarly, the data server could be any database that was available where
proprietary or open source. The invocations for data access, SQL queries, stored
procedures could be in the Web Tier with the queries and procedures in the data
server. In our Web Tier, also we have used XSLT to transform the XML data.
The Web Tier is the major component, and with time, this too could be further
delineated within itself. As transformers, validators and parsers incorporated
newer versions of XML and Schemas there would be further modularization in
this area.
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Client
Web Tier
Data Server
Servlet
XSLT
Presentation Logic
XSLT Processor
HTML
Web
Services
XML
Presentation
Data
Data
Figure 8-1 Solution overview of the Passenger List application
8.3.2 XML in this application
XML plays a key advantage in this application. It provides the full infrastructure
for the data exchange and description between the database and the user
interface, and also within Application Studio as well. WSDL bindings are in XML
format.
Application Developer includes an integrated suite of tools for XML:
ꢀ
Importing of Relational Database information through the wizards and
specifying it in XML Metadata Interchange (XMI) format. This is done when
the database connection is establish.
ꢀ
ꢀ
ꢀ
ꢀ
XML editing and validation
XML Schema and DTD editing, validation and generation between the two
XSLT generation and transformation
Creation of Input and Output forms from JavaBeans, as well as DTD and XML
Schema
ꢀ
Generation of XML from DTD and XML Schema and vice versa.
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ꢀ
ꢀ
ꢀ
Tools to generate XML data from Relational Data and vice versa.
Generation of the DAD and DADX for use in the DB2 UDB XML Extender.
Generation of WSDL bindings.
These tools are used in the development of this application and will be obvious
as the construction progresses.
8.3.3 Technical implementation overview
The technical implementation of the Passenger List application consists of two
projects. The first is the AIRLINE project is where the data access XML files are
generated. The second TRAVEL project builds upon the first to create the
graphical user display and the Web services (Figure 8-2). The approach is
bottom-up approach where the data access is created first. The graphical user
interface is created after, where the input fields are mapped to the tables and
attributes in the database.
AIRLINE project
TRAVEL project
Output Display
HTML
PassengerList
XML Schema
6
1
(XSD)
6(iii)
6(i)
6(ii)
Output Display
XML
Output Diaplay
XML to
PassengerList
PassengerList
Output Display
Data Type
Definition
(DTD)
DTD
2
DTD mapping
PassengerList
Run-time excution
PassengerList
Data Access
Defiinition
Extension
Output Display XSLT
StyleSheet
Data Access
Definition
(DAD)
3
4
(DADX)
5
Servlet
Web Browser
HTML
3
Web Services
2
1
4
Database :Airline
Tables:Passenger,Schedule
XSLT
Processor
PassengerList
Results XML
7
Figure 8-2 Development and running of the Passenger List application
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169
The development of the two projects follows these steps:
1. The AIRLINE project starts with the creation of a XML Schema file. For our
application, the schema is simple: It holds only flight and customer
information. Correspondingly, we also create a database to hold this data.
The schema consists of two tables: ’PASSENGER’ and ‘SCHEDULE’. Each
table consists of four fields. The creation of these tables and the connection is
carried out through the data perspective of Application Developer.
Application Developer is so rich in functionality that to put all its icons on a
single menu would be impossible. The perspectives help to organize all the
functions in an organized way. To access different parts of the project, the
user will have to switch between the perpectives.
2. From the XML Schema, the DTD is generated. This then serves as a mapping
to the relational database tables. The join between the tables are
implemented in the RDB to XML Mapping wizard. Note that the join between
the two tables is carried out in Application Developer, and not in the database.
This serves as a discussion point.
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Discussion:
The advantages and disadvantages of establishing relational database
relationships in Application Developer:
Advantages of using the database:
ꢀ
ꢀ
ꢀ
For application development, relationships between tables are best
established in the database. The tables are shared by many applications,
and therefore is their common point. When a new application is being
developed, the relationship have already being established for the application.
The database is a tried and tested product where joins, triggers, indexes,
etc. are commonplace. These are the forte of any database. Using a
database offers advantages in terms of scalability and performance. This is
important especially for large databases.
XML documents need to be parsed every time they are accessed and the
parsed file must be memory resident during query processing.
Advantages of using the DTD approach in Application Developer
ꢀ
This could be the best approach if the relationships between the tables
were specific to this application.
ꢀ
In e-Business information exchange, DTDs are a common point between
different companies intending to share data. Database schemas and
database relationships are proprietary to an organization and are used for
commercial advantage.This DTD can now be shared between
organizations.
ꢀ
The shared DTD can be agreed to by the organizations, and then using the
XML tools, map parts or all of DTD to the tables in the databases of each
organization.
3. The Data Access Definition (DAD) file is then generated. While generating
this file, a test harness can also be generated. We will use this to unit test the
application until this stage.
4. A new project, the TRAVEL project is created to hold the Web service’s
functionality. The project is a J2EE project. As a first step, a Web services
configuration group is created. After we have copied the DTD and the DAD
into the group, we generate a Data Access Definition eXtention (DADX) file.
The resulting file will have to be customized with the parameters for the flight.
5. The DADX file then serves as a base for the construction of our Web services
through the Web services wizard. This Web service is based on a Java proxy.
The wizard also has the option to generate a Web Services Object Runtime
Framework (WORF) run-time component to dynamically generate a test and
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documentation page. This is made use of at this point to test if the retrieval of
data works properly.
6. A graphical user interface is developed using XSL stylesheets. To start with,
the target HTML file needs to be located. This file would represent the output
page to be displayed. The Application Developer wizards are used to create a
mapping between the output from the database to the output required for
display through a few steps:
a. Generating of the DTD
b. Generation of the XML file for the output data
c. The mapping between the input data and the output display data. The
stylesheet, however, has to be customized.
7. A servlet is developed to transform the data from a hierarchical structure to
HTML using XSLT processors. The servlet is in turn called from a HTML page.
During the execution of the system, only the components in the run-time
components are executed. The following sequence of events follows:
1. The user activates the servlet through the HTML form.
2. The servlet calls the generated Web service classes. It calls the proxy
classes, supplying it the primary key and stores them in a DOM structure.
3. The servlet then passes the DOM structure to the XSL Transformer. The
XSLT stylesheet of the display output is also an input to the transfer. The
transformer produces an HTML file.
4. The newly created HTML file is sent to the Web browser.
Application Developer XML Web Services provide a powerful new tool for
integrating heterogeneous applications over the Internet. Application Developer
provides a fully supported production-ready deployment environment for Web
services based on the Apache SOAP run-time environment. XML plays a central
part by providing a data interchange format that is independent of programming
languages, operating systems, and hardware.
8.4 Enterprise JavaBeans
The Enterprise JavaBeans (EJB) specification provides a framework for creating
reusable business logic components without regard to system infrastructure or
location.
Many business problems today require large, complex systems to solve them.
The trend is to use a multi-tier architecture in which the client communicates with
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an application server (Figure 8-3). The server uses specific business logic and
communicates with some form of persistent data storage, typically, a database.
Web Service
Customise
Membership
Catalog
Interprise Application Server
Figure 8-3 Enterprise Application Server
Depending on what type of client is used, an additional, middle tier may exist
between the client and the application server (for example, a Web server to
provide dynamic HTML).
Developing the middle tier has always been the costly part of system
development. In a perfect world, the developer would only be concerned with the
business logic required to implement the system. But without technologies like
Enterprise JavaBeans, developers also need to be expert in several different
areas:
ꢀ Business logic: Developers must understand the business problem and the
logic required to solve it.
ꢀ Transactions: Developers must correctly group different areas of business
logic into specific transaction contexts.
ꢀ Database access: Developers must understand how to gain access to a
database for retrieving and updating information.
ꢀ State management: Developers must understand how to use
multiprocessing capabilities so different sections of the business logic can be
run concurrently to optimize performance.
And while developing the code for the server application, the developer must
also take into account:
ꢀ
ꢀ
The client and communication protocol to be used to access the server.
The application server that will be used and the APIs it supports.
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ꢀ
The database that will be used and how to interact with it.
EJBs have been designed to provide a framework in which reusable business
logic components can be created without an understanding of the infrastructure
or a concern for where the components will be deployed. And with EJBs, it's
simple to reuse code in other applications once it's been developed to implement
part of a process. (Most business processes can be broken down into a number
of distinct parts, and some of these parts will be common to multiple
applications.)
The simple answer is that EJBs are a server-side component architecture. They
enable a developer to create a component that represents a discrete,
well-defined piece of functionality. Since the interfaces to the component can be
published to other developers, the component can easily be combined with other
components to create a complete application.
In both applications wizards have been extensively used and custom code has
been kept to a minimum. The wizards, by generating the required files, pages
and code, help to jump start the development of the applications while reducing
the learning curve for the developer. They complexity of creating some of the
files is hidden behind from the developer, allowing him more time on customizing
the application.
8.5 The Customer Registration application
The Customer Registration application was developed to demonstrate
Application Developer’s capabilities in the JavaBeans and Enterprise JavaBeans
area. As in any such similar system, there are always two components: The first
called Customer Registration, and the second Customer Retrieval for retrieving
information about the customer that has been registered. The data is prompted
through a Web page and stored in the database. For this application, the
database has a single table and four fields: First Name, Last Name, E-mail, and
Membership number.
8.5.1 XML in this application
XML plays a key advantage in this application. In this application, XML is used as
follows:
ꢀ
ꢀ
Generating of XML from JavaBeans through a wizard. This creates the XML
and XSL accessing JavaBeans. This produces the input and output XSL
forms.
Uses Sun’s Java API for XML Processing (JAXP) to produce the XML data
from the JavaBean.
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ꢀ
Through Java classes maps the XML data to the org.w3c.dom.Element and
also invoking the XSLT processor on the XML document and the XSL
document.
The provision of these capabilities, reduces the development time and the
learning curve of the developer involved in the development of the application.
8.5.2 Technical overview
The Customer Registration system consists of a two main parts. Its has a
registration form where customer data is entered, two Java classes which the
customer information is stored and retrieved from the database. Wizards are
used extensively.
The starting point of the customer registration systems is a JavaBean, which
specifies the getter and setter methods for every attribute of the customer. From
the JavaBean, the JavaBean to XML wizard is used to generate the Web tier. The
wizard leads through a few steps:
ꢀ
It creates the XML and XSL files for all the chosen attributes. Two XSL files
are produced one for the output and another for the input.
ꢀ
ꢀ
It creates the Input and Output forms, which can be customized.
It creates a XML Schema file which describes the customer entity. In this
application there are only four attributes: FirstName, LastName, EMail and
the membership number.
ꢀ
ꢀ
An Java class that converts the customer attributes to a DOM representation.
A Servlet that stores and retrieves the attributes to and from the DOM
representation using the Java class.
As a final part of the system, we carry out a unit test to check if the system as
been properly built until this stage.
For the second part of the project, we build an Enterprise JavaBean framework.
This part of the application also creates the database, and the components
required to access the data. The starting point here is the Enterprise bean
wizard. The wizard guides the developer through the following steps:
ꢀ
ꢀ
ꢀ
Creating a Entity bean with Container Managed Persistence (CMP) fields.
Creating the attributes, and the various classes required for the EJB.
Creating a mapping between the EJB and the relational database fields. In
our application, the database schema is created from the Enterprise bean.
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ꢀ
The wizard only creates a schema file that can be run against the database to
create the table and its attributes. However, this may need to be fine-tuned for
the application.
An Access bean can also be used. This is created through the Access Bean
wizard. An access bean adapts an Enterprise bean to the Java programming
model, by hiding the home and remote interfaces from the developer. They
provide fast access to Enterprise beans by letting the developer maintain a local
cache of Enterprise bean attributes. This wizard also incorporates in JNDI
bindings.
The two components are then integrated by customizing the generated Java
class and the servlet.
The Java class is modified to reference the EJB. A ‘create’ method is developed
to use the EJB’s factory’s ‘create’ method. The servlet is modified to use Java
Server Pages (JSP), the HTML forms developed previously being abandoned.
The JSPs are generated through the JSP wizard. The servlet’s doGet and
doPost methods are modified to interact with the EJB. The doPost is changed to
store information while the doGet method is altered to retrieve data from the
database given the membership number.
The EJB deployed code is generated through an option, and finally the two
projects are tested.
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9
Developing XML Web
services
In chapter nine we discuss how to develop a simple XML Web service using the
Application Developer. To illustrate this we are going to create the Passenger List
application divided in two parts.
ꢀ
ꢀ
Design and develop the Passenger List application using static XML.
Modify the Passenger List application to use an XML Web service.
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9.1 Passenger List application
We separate the development into two phases (Figure 9-1). In the phase one, we
develop the Web tier that returns a static XML using a servlet and XSLT
Processor. In the phase two, we implement a Web service, which returns the
passenger list as a query result.
Client
Web Tier
Data Server
Phase 2
Web
Services
Java
Proxy
Servlet
Phase 2
HTML
XML
Presentation
Data
XSLT Processor
XSLT
Presentation Logic
Data
Figure 9-1 Solution overview of the Passenger List application
In the first phase, we start to design the output message (data) format as an XML
Schema and output presentation as an XSLT. Then create a servlet which works
with them. In the second phase, we generate the Web Service using the XML
9.1.1 Creating the Web tier
The first part consists in getting the passenger list data from a static XML file and
show it as an HTML output page. To do this we need to follow some steps: (See
Figure 9-2.)
1. Design the XML Schema
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2. Generate a DTD from the XML Schema.
3. Generate a sample XML output.
4. Generate the XML file from the schema and add some data to it.
5. Design an HTML output page.
6. Map the XML and the output presentation
7. Generate an XSL file from the map to transform the XML to HTML, in order to
show it as an output page.
8. Develop a simple servlet that reads the XML file and transform it to the HTML
output page using the XSL file and XSLT processor.
ꢀ
Test Passenger List application.
XSD
DTD
doGet
Browser
Servlet
XML
HTML
Mapping
XSL
XSLT Processor
HTML
Figure 9-2 Passenger List application
We are going to create two projects to organize XML and Web application and
lately Web services files separately. The first project is a simple project called
Airline, which will contain the XML files.
Name
Airline
Travel
Type
Simple project
Web project
9.1.2 Create the Airline simple project
To create the simple project from the workbench take this steps:
1. Select File—>New—>Project and create a Simple Project from the Simple
category. Click Next.
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179
2. Set the project name as Airline.
3. Click Finish to complete creating the project.
9.1.3 Create the Travel Web project
To create a Web project from the workbench take this steps:
category.
2. Enter the project name and choose J2EE Web Application Project, click Next.
3. In J2EE Settings Page create a new Enterprise Application Project and enter
Traveler as the project name.
4. Click Next and then click Finish to accept defaults. (See Figure 9-3.)
Figure 9-3 Travel Project
9.1.4 Design the XML Schema
We designed the output message format using XML Schema editor. Basically we
need some description of the contents of the passenger list of a flight. To keep it
simple we are going to design this content as shown in Figure 9-4. Customer
element contains name and frequent flyer membership to describe it. Flight
element contains flight number and departure time attributes and customer
element as a child. A flight can contain multiple customers.
To do this take this steps:
1. Select Airline project.
2. Select File—>New—>XML Schema.
3. Set schema name as passengerList.xsd.
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global element
Flight
attribute
attribute
@flightNo
@departure
global element
Customer
name
element
element
membership
Figure 9-4 PassengerList DOM Tree
The XML Schema editor has a Design view and a Source view. The Outline view
and eliminate the need for a knowledge of XSD syntax, but developers who
prefer to directly edit the file can work with the source view. The Design view
presents a form-based user interface that is synchronized with the outline and
Source view. When a part of the schema is selected in the Outline view, it can be
changed in the Design view.
this:
1. Add two global elements, Flightand Customer, and set type information to
user-defined complex type.
2. Select root node.
3. Right-click Add Global Element (Figure 9-5).
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Figure 9-5 Creating XML Schema
Add Content Model to the complex type.
ꢀ
Select the ct. Right-click Add Content Model.
Add an Element Ref. under the model by:
ꢀ
ꢀ
Select the model right-click Add Element Ref.
Set the reference as customer. Since the flight has one or more customers set
the minimum to one and the maximum to unbounded.
ꢀ
ꢀ
Select ct under Flight.
Right-click Add Attribute. Attribute flightNo must be set as required since it is
a primary key.
ꢀ
Next add two child elements to the customer node. Your XML Schema should
look like Figure 9-6.
Example 9-1 is showing the actual XML Schema.
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Figure 9-6 XML Schema
Example 9-1 PassengerList.xsd
<?xml version="1.0" encoding="US-ASCII"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
xmlns:passenger="http://www.airline.com"
targetNamespace="http://www.airline.com">
<element name="Flight">
<complexType>
<sequence>
<element ref="passenger:Customer" minOccurs="1"
maxOccurs="unbounded"/>
</sequence>
<attribute name="flightNo" type="string" use="required"/>
<attribute name="departure" type="string"></attribute>
</complexType>
</element>
<element name="Customer">
<complexType>
<sequence minOccurs="1" maxOccurs="1">
<element name="name" type="string"/>
<element name="membership" type="string"/>
</sequence>
</complexType>
</element>
</schema>
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9.1.5 Generate XML file
Now we are going to generate the XML File and add some sample data to it. This
data it’s going to be transformed and presented in a HTML output page.
1. Select passengerList.xsd.
2. Right-click Generate—>XML File.
3. Select Airline as the folder name.
4. Enter passengerList.xmlas the filename, click Next.
5. Select Flight as root element, select Create required and optional content,
click Finish.
We need to add some sample data to the XML file. (See Example 9-2.)
Example 9-2 Static XML file
<?xml version="1.0" encoding="US-ASCII"?>
<passenger:Flight departure="8:00pm" flightNo="Air Canada 700"
xmlns:passenger="http://www.airline.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.airline.com passengerList.xsd ">
<passenger:Customer>
<name>John Doe</name>
<membership>123456</membership>
</passenger:Customer>
</passenger:Flight>
9.1.6 Design an output page
Since XML is not a markup language specialized in presentation, we are going to
design an HTML output page to show the data. XSL Transformations (XSLT) will
be used to transform the XML to HTML data. To create the XSL, there are
several approaches as follows:
1. Design an HTML file, then map to the XML using mapping tool. We can use
XSL generator to generate the XSL using the map file.
2. Develop the XSL from scratch. We can use the different wizards in the XSL
editor.
3. Design an XHTML file then generate the XSL file.
HTML and mapping approach
Using this approach, we created a DTD file first. Then generate the XML which
contains HTML tags. Given the XML definition, we can think of HTML as a sub
set of XML. We need to map the static XML file data to HTML tags, in order to be
able to use the XML to XML mapping tool, we are going to create the file
html.dtd, and generate html.xml. (See Example 9-3.)
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Example 9-3 html.dtd
<!ELEMENT html (body)>
<!ELEMENT body (h2, hr, table)>
<!ATTLIST body
bgcolor CDATA #IMPLIED>
<!ELEMENT h2 (CENTER,CENTER)>
<!ELEMENT CENTER (#PCDATA)>
<!ELEMENT table (tr+)>
<!ATTLIST td
width CDATA #REQUIRED
valign CDATA #REQUIRED>
<!ELEMENT tr (td,td)>
<!ELEMENT td EMPTY>
<!ELEMENT hr EMPTY>
After designing our html.dtd we generate html.xml file. To generate html.xml file
take the following steps:
1. Select html.dtd file.
3. Enter Airline as the folder.
4. Enter html.xml as file name, click Next.
5. Set html as root element.
6. Select required and optional content, click Finish.
Example 9-4 shows the generated XML file.
Example 9-4 html.xml source
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html SYSTEM "html.dtd" >
<html>
<body>
<h2>
<CENTER>CENTER</CENTER>
<CENTER>CENTER</CENTER>
</h2>
<hr/>
<table>
<tr>
<td valign="" width=""/>
<td valign="" width=""/>
</tr>
</table>
</body>
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</html>
Generate an XSL file
As we mentioned, we need to have an XSL file to transform. To do this we need
design the way that the XML data is going to be mapped to the HTML tags. For
this example, we are going to do it,as shown in figure Figure 9-7.
<html>
<body>
<h2>
Flight
@flightNo
<CENTER></CENTER>
<CENTER></CENTER>
</h2>
@departure
<hr></hr>
<table>
<tr>
Customer
XSLT
name
<td valign="" width=""></td>
<td valign="" width=""></td>
membership
</tr>
</table>
</body>
</html>
XSL
XML to XML
mapping
Figure 9-7 XML to HTML mapping
Steps to create the XSL file:
1. Switch to XML Perspective if necessary.
2. Start XML to XML Mapping wizard.
4. Enter a name for the mapping file passengerList.xmx, click Next.
5. Add source XML Schema file passengerList.xsd, click Next.
6. Select target html.xml, click Next.
7. Select root element, must be HTML. Click Finish.
Figure 9-8 shows the XML to XML mapping editor.
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Figure 9-8 XML to XML mapping
Mapping XML to HTML
Now we need to map each item from source to the target. To map, click on the
source element then drag on to the target.
Map the elements as follows.
Source
passengerList
flightNo
departure
Customer
name
Target
HTML
CENTER
CENTER
tr
td
membership
td
To match the root, passengerList must be mapped to HTML. The flight number
and departure time will be mapped in the center tag. Since the customers can be
appeared as several lines, Customer element should be mapped to tr.
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Create an XSL from scratch
Creating an XSL from scratch is also useful. The XSL Editor provides a number
of wizards to help you create the content in your stylesheet. This section is
describing how you can create an XSL stylesheet from scratch to format the xml
data into an HTML table.
To create an HTML document, we will add a template to generate HTML header
information as well as to define the output method for the document:
1. Position the cursor to an empty line after the <xsl:stylesheet> element in
the html.xsl file.
2. In the menu bar, select XSL->HTML Template. This will create an
<xsl:output> element that will output the result in HTML, and a template that
will emit an HTML header with an <xsl:apply-templates>rule to will process
all the immediate children in the passengerList.xml file.
Next, we will create a template that will produce an HTML table:
1. Position the cursor to an empty line after the </xsl:template>.
2. In the menu bar, select XSL->HTML Table. This will bring up the XSL Table
Wizard.
3. Select the Flight element as the context node for building the HTML table.
This implies that all the children of the Flight element will be added as
columns in the table.
4. Check the Wrap table in a template check box to indicate that we want to
wrap this table in a new template.
5. Check the Include Header check box to indicate that we want to include a
header in this table.
6. Optionally, click Next to go to the next page to add a table border and
background color for the table.
7. Click Finish. This will create a new Flight template in your html.xsl file that will
produce an HTML table.
Generating XSL from XHTML
This will enable you to separate out the presentation logic from the dynamic data
in an existing HTML document. It extracts the data into an XML file and the
presentation data into two XSL files. Once the separation is completed, you can
use XSLT technology to combine new data that is defined in XML format with the
generated XSL files to create new HTML Web pages. To use this technology
requires the following steps:
1. Prepare the HTML file for generation by converting it into a well-formed XML
file with a .xhtml extension.
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2. Create a template file that contains the annotation tags.
3. Invoke the Generation wizard.
One of Application Developer example is showing how to generate XSL from
HTML using XHTML technology step by step. To see in detail, install
HTMLToXSL Project using New->Example wizard.
9.1.7 Testing the XSL
To test the XSL, select passengerList.xml then, use Apply XSL as HTML from
the context menu:
1. Select PassengerList.xml.
2. Right-click Apply XSL -> as HTML.
3. Select workbench projects.
4. Select passengerList.xsl.
5. Click Finish.
Then the XSL Debugger is opened. Use Open the browser on the transformation
result toolbar button to view the result (Figure 9-9).
Figure 9-9 Testing the XSL
9.1.8 Developing the servlet
The servlet that we are going to develop is simple. It implements the doGet
method, reads the XML file generated in 9.1.5 “Generate XML file” on page 184,
and transforms it to an HTML file using the XSL file generated in “Generate an
XSL file” on page 186. See Example 9-5. Create the GetPassengerListServlet in
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Travel project. We used com.ibm.itso package. WAS_V4_XALAN variable is
required in the Java Build Path to create this servlet.
Example 9-5 GetPassengerList Server doGet method
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, java.io.IOException {
String xslFile = "/WEB-INF/xsl/passengerList.xsl";
String xmlFile = "/WEB-INF/passengerList.xml";
try
{
resp.setContentType("text/html");
PrintWriter out = resp.getWriter();
TransformerFactory tFactory = TransformerFactory.newInstance();
Transformer transformer = tFactory.newTransformer(
new StreamSource(
getServletContext().getResource(xslFile).toExternalForm()));
StreamSource source = new StreamSource(
getServletContext().getResource(xmlFile).toExternalForm());
transformer.transform(source,new StreamResult(out));
}
catch(Exception ex)
{
System.out.println("Error in doGet "+ex.toString());
}
}
The ServletContext provides own getResource method. It returns the resource
located on the location of the current Web application. To load files from the
current WAR file, you need to specify the file name, start with /WEB-INF/. In this
case you need to copy the following files into the /WEB-INF/ directory:
ꢀ
ꢀ
ꢀ
passengerList.xml (sample data)
PassengerList.xsd (required by passengerList.xml)
passengerList.xsl (create /WEB-INF/xsl directory and put it inside)
Using JAXP
As we mentioned about JAXP, it provides a standard Java interface to many
XSLT processors. We used three JAXP classes in our servlet.
ꢀ javax.xml.transform.Source
This interface is used to read XML and XSLT file. This can read from a stream
type object such as an InputStream, or a Reader.
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ꢀ javax.xml.transform.TranfrormerFactory
This is responsible for crating transformer object. TrasformerFactory is
abstract, and its new instance method is used to instantiate an instance of
Transformer class.
ꢀ javax.xml.transform.Transformer
This instance is used to perform the actual transformation. It is not tread-safe,
so in a threaded servlet environment; this should be an instance variable. By
this restriction, you need to load XSLT on every request.
9.1.9 Test the passenger list application
In this section we test the passenger list application. You need to copy the
passengerList.xsl to the /WEB-INF/xsl folder, and copy the passengerList.xml to
the /WEB-INF folder in the Travel project. To test the application we have to start
a WebSphere test environment, and call the servlet from the browser. Since the
servlet does not need an input parameter, and implements doGet method, it can
be called using the URL directly.
Figure 9-10 passengerList result page
9.1.10 Compiling XSL
Since the Transformer is not a thread-safe, we need to instantiate the
Transformer on every request. Actually, in the doGet method, it is loading XSL
file from the stream every request. The XSLT Complier enables that it load in to
the Java vm as an object and reuse in the servlet instances. JAXP supplies the
template’s interface to provide consistency. This interface has newTransformer
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method. The instance of the Templates can be instantiate using newTemplates
method of TransformerFactory class:
TransformerFactory transFact = TransformerFactory.newInstance();
String xslName = "/WEB-INF/xsl/Passenger.xsl";
URL stylesheetURL = getServletContext().getResource(xslName);
String xsltSystemID = stylesheetURL.toExternalForm();
template = transFact.newTemplates(new StreamSource(xsltSystemID));
Using the templates, we can load and compile the XSL into the memory while we
are initializing the servlet. Doing this in the init method, the servlet can hold the
Templates as a global variable. To get the instance of Transformer, use
newTransformer method of the template:
Transformer transformer = template.newTransformer();
9.2 Creating a Web service
In the previous application we were extracting the information from an static XML
file. Now, we are going to extract the information from the database using an
XML Web service. We are going to generate a Web service using the previous
generated XML files, so the flow would be as shown in Figure 9-11.
Web Service
XSD
Airline
DB
Mapping
DTD
DAD
DADX
Figure 9-11 XML Web service
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We are going to discuss:
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Creating the database tier
Generating DTD from XML Schema
Creating DAD file using RDB to XML mapping
Creating Web service from DADX file
Testing a Web service
Modifying the Passenger List application to use Web service
9.2.1 Create the database tier
See database specification in figures below.
Column name
Flight
Data type
VarChar
VarChar
VarChar
Maximum length
30
20
10
Name
Membership
Column name
FlightNo
Data type
VarChar
VarChar
VarChar
VarChar
Maximum length
30
10
10
10
AirCraft
Departure
Arrival
In order to create the necessary files to access the database, we need to create
1. Open the database perspective.
2. Click Window—>Open Perspective—>Data.
3. Select DBServers tab.
4. Right-click New Connection.
The connection must be configured as shown in Figure 9-12 on page 194. After
creating the connection import it to your project:
1. Select the connection.
2. Right-click Import to folder.
3. Select your project’s folder and click OK.
4. Click Finish.
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Figure 9-12 Database Connection panel
9.2.2 Generate DTD file
In addition to the XSD Editor, WebSphere Studio Application Developer also has
the DTD Editor. We refer to both XSD and DTD as schemas. Application
Developer has extensive support for schemas, including tools for validating
schemas, converting between XSD and DTD, generating schemas from sample
XML instance documents, generating sample XML documents from schemas,
and generating Java classes and relational database schemas from XML
Schema.
XML Extender only supports DTD. We need the DTD file because it is going to
be useful when mapping our output message format elements to the database
fields in “Generate an XSL file” on page 186.
Select the Navigator view and right-click
passengerList.xsd—>Generate—>DTD (Figure 9-13).
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Figure 9-13 Generated DTD File
9.2.3 Loading DTD into XML Extender
Before you start, you need to load the DTD into DB2 XML Extender to use. If you
did not initialize the Extender, you can with the following commands:
db2 "bind '%DB2EXTENDER%\bnd\@dxxbind.lst'"
db2 "bind '%SQLLIB%\bnd\@db2cli.lst'"
Note: Default directory of DB2 XML Extender is c:\dxx and SQLLIB is
c:\Program Files\SQLLIB.
You need to enable the database to use with DB2 XML Extender. Run following
command to enable the airline database:
dxxadm enable_db AirLine
Now you need to install the passengerList.DTD into DB2 to run the
PassengerList as a stored procedure under DB2 XML Extender:
db2 "insert into db2xml.dtd_ref values('passengerList.dtd',
db2xml.XMLClobFromFile('passengerList.dtd'), 0, 'user1', 'user1', 'user1')"
Note: PassengerList.dtd must be located in local folder. DB2 does not load it
from the networked drive.
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9.2.4 Creating DAD file using RDB to XML mapping
After defining the schema for the output message and setting our database, we
can define the listPassenger operation that retrieves the information from the
database. Here we plan to use the DB2 XML Extender run-time component to
execute the operation and generate the XML result. We must define a DAD file
for the retrieval operation.
used to associate the XML document structure to a DB2 database. Basically, it
provides the mapping between the elements or attributes of an XML document
and the table columns, and the details of how a request for an XML document is
to be handled.
To see how to map the database to the DTD file see Figure 9-14.
Schedule
DTD
flightNo
aircraft
departure
arrival
<flight>
<flightNo>
<departure>
<Customer>
<name>
<membership>
Passenger
flight
name
membership
Figure 9-14 RDB to XML mapping
The RDB to XML Mapper tool, shown in Figure 9-16, helps us define the
mapping from the database to the XML result:
1. Turn to XML perspective if necessary.
2. Select the project and right-click New—>RDB to XML Mapping.
3. Enter passengerList.rmxas the name of the file, click Next.
4. Select RDB Table to XML Mapping, click Next.
5. Select the source tables Passenger and Schedule, click Next.
6. Then select the target DTD file passengerList.dtd, select Flight as the root
element, and click Finish.
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To define the mappings we select the column of the database in the tables view
mapping to our definition. Since we are using two tables we have to specify the
join conditions.
ꢀ
Click Mapping—>Edit Join Conditions.
Remember that we are using flightNo as a primary key, so they must match in
both tables. See Figure 9-15.
Figure 9-15 Edit Join Conditions
The complete definition is stored in passengerList.rmx, which is an abstract
representation of the mapping.
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Figure 9-16 RDB to XML mapping
The mapper generates a concrete mapping in a DAD file called
passengerList.dad, for the DB2 XML Extender.
In the Navigator view:
1. Select passengerList.rmx.
2. Right-click Generate DAD.
3. Set passengerList.dad as the name of the file.
4. Choose your project folder, then click Next.
5. In Dad Generation Advanced Options and Generate Test Harness, click Next
to accept defaults.
6. Click Finish.
The wizard will show you the generated DAD file. See Figure 9-17.
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Figure 9-17 Generated DAD file
9.2.5 Create the Web Service from DADX file
We are going to create a Web Service to encapsulate the extraction of the
passenger list from the database. Web Service example which lists all the
passengers that have tickets for a flight. Here we take a more top-down
approach by first designing the format of the output message as an XML
Schema. We then map the schema elements with the database fields and
express the mapping as a DAD file that can be executed by the DB2 XML
Extender. The DB2 XML Extender allows us to handle XML documents that have
complex hierarchical structures. We then work on a user interface to display the
output into HTML and test its behavior.
The DB2 XML Extender provides stored procedures that can execute DAD files.
The Web Service files are going to be in a different project called Travel.
DAD Extension
DAD Extension (DADX) is an XML technology for rapidly creating Web services
that access relational databases such as DB2 UDB. When combined with the
DB2 XML Extender, DADX supports mapping relational data into complex XML
documents and storing XML documents in the database. DADX consists of an
XML document format and a Java runtime component that work with Apache
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SOAP 2.2 and that run on J2EE compliant application servers like WebSphere
and Tomcat. To create a new Web Service, the developer authors SQL
statements in a DADX document and deploys it to the application server. The
DADX runtime executes SOAP requests sent to the new service and provides
additional support including HTTP GET and POST bindings, test page and
WSDL generation, and translation of DTD into XML Schema. This document
describes the DADX document format and runtime. In this section, we will
generate the DADX from the DAD.
Web services and DB2 XML Extender
The DB2 XML Extender makes it easy to create XML applications using DB2.
DB2 XML Extender consists of a set of stored procedures, user defined types
(UDT) and user defined functions (UDF) that enable an application programmer
to store and retrieve XML data using DB2. DB2 XML Extender allows XML
documents to be stored intact, and optionally indexed in side tables, using the
XML Column access method, or as a collection of relational tables using the XML
Collection access method. DXX uses a DAD to define the mapping between XML
and relational data.
Web services are XML based application functions that can be invoked over the
Internet. It is, therefore, natural to use DB2 XML Extender to implement Web
services. This document specifies a DADX that makes it easy to create Web
services using DB2 XML Extender. A DADX document specifies how to create a
Web Service using a set of operations that are defined by DAD documents and
SQL statements. A Java component, the DxxInvoker, provides the runtime
support for invoking DADX documents as Web services in Apache Simple Object
Access Protocol (SOAP) 2.2 which is supported by WebSphere Application
Server and other J2EE servlet engines.
The DADX Group
The resources for all DADX Web Service groups are stored in the directory
WEB-INF/classes/groups where WEB-INF is the directory used by J2EE Web
applications to store resources that are not directly available to HTTP requests.
This means that users cannot see the contents of your DADX files. DADX files
contain the implementation of the Web services, and are therefore, similar to
Java classes.
The classes directory is part of the Java class path for the Web application. This
means that your DADX files can be loaded by the Java class loader and that your
Web application can execute directly from its WAR file if your application server
supports that mode of operation.
Within the groups directory each group of DADX Web services is stored in a
directory with the same name as its servlet instance. The DxxInvoker servlet
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determines where to find DADX files by looking for a directory that matches its
servlet name.
Now we are creating a Web Service DADX Group configuration in the Travel
Project to contain all the Web Service files. A DADX Group contains connection
(JDBC and JNDI) and other information that is shared between DADX files within
the group:
1. Select the Travel project, click File—>New—>Other.
2. In the New Window, create Web Services DADX Group Configuration from
the Web Services category. Click Next.
3. Select Travel project, click Add Group, enter TravelGroupas the name, and
click Finish.
The group.properties File
The database connection information, and other parameters, are defined in the
group.properties file for the group which, in our example, is stored in the
WEB-INF/classes/groups/travelGroup directory.
The group.properties file is a standard Java properties files. The properties have
the following meanings:
Properties in group.properties:
initialContextFactory The Java class name of the JDNI initial context factory
that is used to locate the DataSource for the database.
datasourceJNDI
dbDriver
The JNDI name of the DataSource for the database.
The Java class name of the JDBC driver for the
database.
dbURL
The JDBC URL of the database.
The user ID for the database.
userID
password
namespaceTable
autoReload
The password for the database.
The resource name of the namespace table.
The boolean automatic reloading mode.
reloadIntervalSeconds The integer automatic reloading time interval in
seconds.
groupNamespaceUri
enableXmlClob
The URI prefix for automatically generated namespaces
for the WSDL and XSD documents.
The boolean mode for enabling the XML CLOB stored
procedures.
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Tip: Since the group.properties file may contain a user ID and password, it
should be stored in a secure file system to prevent unauthorized access. In
addition, the password can be stored in an encoded format to add further
security. The encoding makes the password look like a long, random string of
characters that are hard to memorize. This precaution prevents the password
from being exposed to coworkers who might be looking over your shoulder
while you edit the file. However, encoding is no substitute for proper file
access control since the encoded password can be easily decoded.
Generating the DADX
Copy passengerList.DTD and passengerList.DAD files from Airline project into
the TravelGroup folder in Travel project.
Now we are going to create the DADX file:
1. Switch to resource perspective if necessary.
2. Select TravelGroup folder, click File—>New—>Other.
3. In the New window, create a DADX file from the Web Services category click
Next.
4. Since we are not using a query we can skip the Select SQL statements by
clicking Next.
5. Add passengerList.dad file from the TravelGroup folders and click Next.
6. It is not mandatory but, we can change the name of the retrieve and store
operations. Enter passengerList.dadxas the name of the file, and modify the
name of the store and retrieve operations to store_passengerList_rdb, and
retrieve_passengerList_rdb, respectively as shown in Figure 9-18.
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Figure 9-18 DADX Generation
DADX operations
The proceeding discussion used a DADX document that employed a three types
of operation: query, update, and retrieveXML. The XML Collection operations use
the DXX stored procedures. The SQL operations use normal SQL SELECT,
UPDATE, INSERT, DELETE and CALL statements, and can be used for XML
Column operations by employing the DXX UDTs and UDFs. When using the
SQL operations, parameters may be defined using XSD elements as well as
simple types. For the query operation, XSD elements may be associated with the
column values in the result set. For call operations, parameters may be declared
as in, out, or in/out.
XML Collection operations:
ꢀ
ꢀ
retrieveXML
storeXML
SQL operations:
ꢀ
ꢀ
ꢀ
Query
Update
Call
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<retrieveXML>
The retrieveXML operation generates zero or one XML documents from a set of
relational tables using the XML Collection access method.
This operation is currently implemented by the dxxGenXML or dxxRetrieveXML
stored procedures, or the new dxxGenXMLClob and dxxRetrieveXMLClob
depending on the value of the useXmlClob property defined in the
group.properties file.
The new stored procedures are faster and more portable but differ in that they
return at most one document. To make the semantics of the operation
independent of the stored procedures used to implement them, only a single
document is requested when using the old stored procedures. This change
affects the XML Schema generated for the output in preliminary versions of this
specification (maxOccurs="unbounded" previously, but maxOccurs="1" now).
This operation is implemented by dxxGenXMLClob since a <DAD_ref> element
is used but would be implemented by dxxRetrieveXMLClob if a
<collection_name> element had been used.
The dxxGenXMLClob stored procedure takes as arguments a DAD document
and an optional override. The override can be either SQL or XML. If the override
is SQL then the DAD must use SQL mapping. If the override is XML then the
DAD must use RDB_node mapping. Our DAD is using RDB_node as well. If an
override is defined, then the operation can also define one or more <parameter>
elements. The parameters form the input message. DxxInvoker extracts the
parameters from the input message, validates them, and then substitutes them
into the override by replacing the parameter markers, e.g. :flightNo.
The dxxGenXMLClob returns zero or one XML documents that satisfy that DTD
referenced by the DAD file. DxxInvoker invokes the dxxGenXMLClob stored
Since we want to query the database using a search criteria, we need to use an
XML_override tag and a XPath expression in the DADX file to do it. The
XML_override tag allows you to specify your XPath expression for doing a query.
We need to specify that we are querying using flight number, so we customize
our DADX file as shown in Example 9-6:
1. Add an <dadx:XML_override> element in the DADX editor
2. Add an XPath expression to specify the parameter.
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Example 9-6 Updated DADX file
<dadx:retrieveXML>
<dadx:DAD_ref>passengerList.dad</dadx:DAD_ref>
<dadx:XML_override>
/Flight/@flightNo=:flightNo
</dadx:XML_override>
<dadx:parameter name="flightNo" type="xsd:string"/>
</dadx:retrieveXML>
<storeXML>
The storeXML operation stores an XML document in a set of relational tables
using the XML Collection access method. The DAD document that defines the
collection must use the RDB_node mapping method. This operation is
implemented by dxxShredXML if a <DAD_ref> element is used and by
dxxInsertXML if a <collection_name> element is used. The dxxShredXML stored
procedure takes a DAD document and an XML document as input.
Deploying the Web service
having the dadx file ready, we can create and deploy the web service. We use the
Web services wizard, to generate the Java client proxy that we are using in a
client application:
1. Select TravelGroup folder.
2. Copy passengerList.dad into the TravelGroup directory.
3. Right-click New—>Other, and in the New window create a Web Service from
Web Services category, click Next.
4. Select DADX Web Service as Web service type.
5. Set Java proxy as client proxy type, set check boxes, as shown in Figure 9-19,
and click Next.
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Figure 9-19 Web Service settings
6. In the Web Service setup window, click Next to accept defaults.
7. Then choose the DADX file in which the Web service is based, click Next.
8. After doing so, we need to set the database name, the user ID and the
password to access the database. Also, change the jdbc driver if necessary,
click Next.
We also need to modify the namespacetable.nst file in order to add a mapping
entry.
10.Double-click namespacetable.nst in your TravelGroup folder.
11.Add a mapping entry for passegerList.dtd, as shown in Example 9-7.
Example 9-7 namspacetable mapping entry
<mapping dtdid="passengerList.dtd"
namespace="http://www.airline.com/passengerList.dtd"
location="/passengerList.dtd/XSD"/>
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9.2.6 Test the Web Service
A Web Service defined by a DADX file is self-describing. It dynamically
generates a documentation and test page, WSDL documents, and XML Schema.
The following HTTP GET URL requests the documentation and test page:
The following HTTP GET URL requests the WSDL description of the service:
For HTTP SOAP, the services are invoked by sending SOAP envelopes using
POST to the URL:
We are ready to test the Web Service:
1. Switch to server perspective and start the WebSphere test environment.
3. Enter:
http://localhost:8080/Travel/TravelGroup/passengerList.dadx/TEST as
the URL.
4. Click retrieve_passengerList_rdb link, enter the flight number and click
Invoke. See Figure 9-20.
Figure 9-20 Testing Web Service
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We are going to modify our passenger List application, to use the Web Service.
The new approach includes an input form where the user can enter the flight
Number to get the passenger List. The servlet receives this information and uses
the Java proxy generated in 9.2.5 “Create the Web Service from DADX file” on
page 199. The Web services returns XML data, which is transformed using XSLT
Processor by the servlet, and returns and HTML response. See Figure 9-21 on
page 208.
Servlet
Web
Airline
DB
Service
SOAP
Java
Proxy
XSLT
Processor
HTTP
XSLT
XML
Data
HTML
Figure 9-21 Passenger List application
Mapping DTDIDs to XSD namespaces and locations
The DTDID used by DXX is typically the local file path of the DTD. DXX retrieves
the DTD either from the file system or the DTD_REF table. However, the use of a
local file path is not appropriate for Web services since the result is sent to
remote clients that do not have access to the server file system. The correct way
to specify the document structure is by giving the namespace and location of an
XML Schema (XSD) document for the result. The namespace and location are
specified using an <import> element in the WSDL document that describes the
Web Service.
DxxInvoker must, therefore, associate an XSD namespace and location with
each DTDID that is used in the DAD documents that are referenced by the
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service. The mapping between DTDIDs and XML namespaces is defined by the
following group.properties parameter:
ꢀ
namespaceTable is a reference to an XML resource that defines the mapping
between DTDIDs and XSD namespaces and locations.
The algorithm for mapping a DTDID to an XSD namespace and location is as
follows:
ꢀ
Lookup the DTDID in the namespaceTable. If an entry exists then use the
defined namespace and location.
ꢀ
Otherwise, the DTDID cannot be mapped so throw an exception.
Modifying the XSL file
We need to modify the namespace in passengerList.xsl since the Web Service
has added some lines that were not specified on the DTD file.
ꢀ
Add namespaces specified in the Web Service returned format shown
Example 9-8.
Example 9-8 Namespaces
xmlns:xsd1="http://tempuri.org/Travel/TravelGroup/passengerList.dadx/XSD"
xmlns:pl="http://www.airline.com/passengerList.dtd"
The returned root element from the Web Service is different, since it uses the
name of the operation. Change XSL file as shown in Example 9-9.
Example 9-9 Changing root element
<!--======================================================================-->
<!--
The Root Element
-->
-->
<!-- The "Root Element" section specifies which template will be
<!-- invoked first thus determining the root element of the result tree. -->
<!--======================================================================-->
<xsl:call-template name="html"/>
</xsl:template>
Since we introduce a variable named pl in the namespace, we have to use it in
every occurrence of an element like Flight, Customer, and so on. See completed
xsl file in Example 9-10.
Example 9-10 passengerList.xsl
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
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xmlns:xsd1="http://tempuri.org/Travel/TravelGroup/passengerList.dadx/XSD"
xmlns:pl="http://www.airline.com/passengerList.dtd"
version="1.0"
xmlns:xalan="http://xml.apache.org/xslt">
<xsl:output method="xml" encoding="UTF-8" indent="yes"
xalan:indent-amount="2"/>
<xsl:strip-space elements="*"/>
<!--======================================================================-->
<!-- This file contains an XSLT transformation stylesheet which
-->
<!-- constructs a result tree from a number of XML sources by filtering -->
<!-- reordering and adding arbitrary structure. This file is
<!-- automatically generated by the XML Mapper tool from IBM WebSphere
<!-- Studio Workbench.
-->
-->
-->
<!--======================================================================-->
<!--======================================================================-->
<!--
The Root Element
-->
-->
<!-- The "Root Element" section specifies which template will be
<!-- invoked first thus determining the root element of the result tree. -->
<!--======================================================================-->
<xsl:template match="xsd1:retrieve_passengerList_rdbResult">
<xsl:call-template name="html"/>
</xsl:template>
<!--======================================================================-->
<!--
Remaining Templates
-->
<!-- The remaining section defines the template rules. The last template -->
<!-- rule is a generic identity transformation used for moving complete -->
<!-- tree fragments from an input source to the result tree.
-->
<!--======================================================================-->
<!-- Newly-defined element template -->
<xsl:template name="html">
<html>
<xsl:call-template name="body"/>
</html>
</xsl:template>
<!-- Newly-defined element template -->
<xsl:template name="body">
<body>
<xsl:attribute name="bgcolor">
<xsl:value-of select="'#FFFFCC'"/>
</xsl:attribute>
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<xsl:call-template name="h2"/>
<hr></hr>
<xsl:call-template name="table"/>
</body>
</xsl:template>
<!-- Newly-defined element template -->
<xsl:template name="h2">
<h2>
<CENTER>
<xsl:value-of select="pl:Flight/@flightNo"/>
</CENTER>
</h2>
</xsl:template>
<!-- Composed element template -->
<xsl:template match="pl:Customer">
<tr>
<td>
<xsl:value-of select="pl:name/text()"/>
</td>
<td>
<xsl:value-of select="pl:membership/text()"/>
</td>
</tr>
</xsl:template>
<!-- Newly-defined element template -->
<xsl:template name="table">
<table>
<xsl:apply-templates select="pl:Flight/pl:Customer"/>
</table>
</xsl:template>
<!-- Identity transformation template -->
<xsl:template match="*|@*|comment()|processing-instruction()|text()">
<xsl:copy>
<xsl:apply-templates
select="*|@*|comment()|processing-instruction()|text()"/>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
Creating HTML input form
In order to let the user enter a search key, we are going to design a HTML form
and a servlet. This servlet is going to call a xsl processor using jaxp. For an
example of an input form, see Figure 9-22.
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Figure 9-22 Input form GetPassengerList.html
This input form sends a flight number entered by the end user to the servlet. The
servlet calls the Web Service using its Java proxy, and transfer the returned XML
format into an HTML page and call it, See Figure 9-23 on page 213. The Java
proxy was generated by the Web Service wizard, and the source code of this
proxy is provided. We only need to know which method to call.
Using Java proxy
The Java proxy that is generated by Web services wizard enables to access to
the Web services by method call instead of standard Web Service invocations.
To use PassengerListProxy, instantiate the proxy and call the
retrieve_passengerList_rdb method which is we defined in the Web services
wizard. The result can be a source for the Transformer class:
passengerListProxy proxy = new passengerListProxy();
proxy.retrieve_passengerList_rdb_(key);
JAXP DOM I/O
To make the result as an input for the transformer, creating
org.w3c.dom.Document format is the best way to do. To create the document
from the result of the Web Service, use following statement:
DOMSource domSource = new DOMSource(proxy.retrieve_passengerList_rdb_(key));
transformer.transform(domSource, new StreamResult(pw));
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Even the DOM transformation is fast, the DOM is memory intensive, the DOM
data which is generated dynamically as the result of Web Service (or database
query) will be better than generating from the DOM from a stream inside of the
transformer.
Figure 9-23 passengerList result page
Conclusion
XML Web services provide a powerful new technology for integrating
heterogeneous applications over the Internet. WebSphere Application Server
provides a fully supported production-ready deployment environment for Web
services base on the Apache SOAP run-time environment. XML plays a central
role by providing a data interchange format that is independent of programming
languages, operating systems, and hardware.
WebSphere Studio Application Development is a new development environment
that supports the fully life cycle for Web services development with support for
SOAP, WSDL, and UDDI, and includes a powerful suite of XML tools. Using this
environment, developers can easily transform existing components, such as
JavaBeans, EJB beans, and SQL statements, into Web services, and can
incorporate Web services into new applications.
Chapter 9. Developing XML Web services
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10
Development of XML-based
Enterprise applications
This chapter provides the reader with an opportunity to learn about the
development of XML based Enterprise applications. The chapter describes in
detail the process of developing such type of applications using Websphere
Studio Application Developer. This information is provided through building a
sample customer registration scenario.
In this chapter, the following topics are described:
ꢀ
ꢀ
ꢀ
Architecture of XML-based Enterprise applications
Development of such applications using Application Developer
Deployment and testing of the solution on the Application Developer
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215
10.1 XML based Enterprise application architecture
Most of the contemporary Enterprise Edition (J2EE) applications rely on HTML
for the presentation layer. This minimizes the benefits provided by the flexibility of
the distributed multi tier J2EE, since the target audience is limited to users of
Web browsers. As the pervasive world is widely evolving, future audience will be
the users of new devices. Accordingly, we need to decouple content from
presentation logic and become independent of the audiences’ devices. XML’s
Web publishing capabilities are the key solution for providing that level of
transform XML documents into other textual documents, compliant with the
desirable target devices. The focus of this chapter will only be on using XSLT to
transform XML to HTML, but you can use XSLT to transform XML to any
desirable markup language, for example WML, VoxML,.etc.
The J2EE layered architecture, illustrated in Figure 10-1, can minimize the cost
of evolving an application’s functionality and updating its implementation
technology. These layers can be broadly categorized as the client layer, the Web
tier layer (which includes the controller servlet, validation logic, presentation
data, and presentation logic), the app server layer, and the data server layer.
Client
Web Tier
AppServer
Validation Logic
Business Logic
(EJB)
Servlet
Request Handler
HTML
Presentation
Data
Data
Object
XSLT Processor
XML
XSLT
Data
Presentation Logic
Data Server
Figure 10-1 Multi-tier solution architecture
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In order to understand how these components interact with each other, have a
deep look at 10.2, “Solution outline for customer registration sample” on
page 217.
10.2 Solution outline for customer registration sample
An overview of the sample application can be found in Chapter 8. This section
discusses the interaction between solution components, before we progress to
building the application. There are two possible ways of interaction between the
components of the system. This difference in interaction is based on the target
functionality. We focus on the set of interactions for storing data, then we discuss
the set of interactions for retrieving customer information.
Customer registration
When registering, the user enters the necessary registration data in the form
provided by the HTML in the client layer. When the user clicks the Submit button,
a series of interactions between system components take place, as indicated in
Figure 10-2 on page 218, and in the following steps:
1. The HTML sends the customer registration data through the HTTP request to
the servlet, invoking the servlet doPost method.
2. The servlet extracts the data from the request, and creates a new
CustomerXML object. Now the servlet invokes the create method in the
CustomerXML object.
3. The CustomerXML object’s create method, instantiates a new
CustomerFactory, and invokes its create method having the customer
registration data.
4. The factory creates a customer entity bean with the customer’s registration
information.
5. The entity bean’s data is saved into the customer table in the database.
6. The customer entity bean is returned to the CustomerXML.
7. The CustomerXML executes its produceDOMDocument method, which
converts the Customer entity bean into XML data.
8. The XSLServlet applies the Customer Result XSL on the generated XML
data, by invoking the XSLT Processor.
9. The XSLT Processor applies the stylesheet on the XML data, generating an
HTML representation for the customer registration data.
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217
1
2
Customer XHL
(DOM)
HTML
XSL Servlet
7
3
6
9
Customer
Factory
XML Data
4
XSLT
Processor
9
Customer XSL
10
Customer
(Entity Bean)
Web
Browser
HTML
Customer
5
Result XSL
DB
Figure 10-2 Customer registration scenario outline
Retrieving customer information
When retrieving customer data, the user enters the membership number of the
customer whose information is to be retrieved in the form provided by the HTML
in the client layer. When the user clicks the Submit button, a series of interactions
between system components take place, as indicated in Figure 10-3 on
page 219, and in the following steps:
1. The HTML sends that value to the servlet through the HTTP request to the
servlet, invoking the servlet doGet method.
2. The servlet validates that the user has entered a membership value. Then the
servlet invokes the findByPrimaryKey method that belongs to the
CustomerFactory class, using the input membership value.
3. The CustomerFactory retrieves the data from the database, and constructs a
customer entity bean setting its attributes with the values returned from the
database.
4. The servlet provides the returned entity bean to the CustomerXML, which
converts that bean into a DOM representation.
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5. The servlet invokes the XML to HTML transformation using the XSLT
processor given the XSL for the target HTML. When the transformation is
performed, the user can view the retrieved customer information on the Web
browser.
Customer
Factory
HTML
XSL Servlet
1
2
4
Customer
5
3
XSLT
Processor
7
XML Data
6
8
HTML
Customer XML
(DOM)
Customer XSL
DB
Web
Browser
Customer
Result XSL
Figure 10-3 Retrieving customer data scenario outline
10.3 Developing the customer registration sample
In order to develop this J2EE application, we divide the process into four phases:
ꢀ
ꢀ
Creating the Web tier
Development of the back-end layer, which includes the business logic (EJB)
and the database schema
ꢀ
ꢀ
Integrating the Web tier with the back-end layer
Development of the client layer
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10.3.1 Creating the Web tier
In order to create the Web tier, the Websphere Application Developer provides a
wizard for doing that. Given a JavaBean, the wizard generates the Web tier
components as shown in Figure 10-4.
JavaBean XML
Client Wizard
JavaBean
Generates
XSL
Servlet
XML
Schema
DOM
XSLTs
Web.XML
Figure 10-4 JavaBean to XML client wizard
Preparing to create the Web tier
Websphere Application Developer provides a wizard that facilitates the creation
of the Web Tier. But, before we start using that wizard, we must perform some
configuration steps.
Project configuration
Create a J2EE Enterprise Application project called CustomerInfo as J2EE 1.2
Compliant. The following projects are generated automatically unless you
change the names:
CustomerInfo
EAR Project
CustomerInfoClient Test Client
CustomerInfoEJB
CustomerInfoWeb
EJB Project
Web Project
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JavaBean creation
Create a new JavaBean called Customer into the CustomerInfoWeb project, by
choosing the Java perspective, and select File—>New—>Class, edit the class
name to be Customer, and select Finish. Edit the Customer class, creating the
attributes, and generate setter and getter methods according to the class
specification in Figure 10-5.
Figure 10-5 Customer JavaBean class specification
Note: Application Developer V5.0 supports both J2EE 1.2 and 1.3. In this
chapter, we are using J2EE 1.2 and EJB 1.1 to run on WebSphere Application
Server V4. If you choose J2EE 1.3, you need to use EJB 2.0 and WebSphere
Application Server Test Environment V5.
Creating the Web tier
1. Close the Java perspective as we no longer require it, and switch to the XML
perspective.
2. At the top menu of your workspace, click File—>New—>Java Bean
XML/XSL Client to invoke the JavaBean to XML wizard.
The wizard opens Figure 10-6, indicating the creation of XML and XSL
accessing JavaBeans.
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Figure 10-6 JavaBean XML/XSL client wizard
3. Leave all defaults as they are, click Next.
Now we need to choose the JavaBean, the methods, and the properties that
we intend to include in our application:
4. Select Browse to get a list of the available classes in your workspace.
Choose your customer JavaBean, as shown in Figure 10-7.
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Figure 10-7 JavaBean XML/XSL client: JavaBean selection
5. After you choose your bean, click OK to go to the dialog in Figure 10-8, and
click Introspect to introspect the bean if you did not get any methods, where
you will select the bean properties that you want to include. In this scenario,
we choose membership, firstName, lastName, and e-mail.
6. Click Next.
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Next we design the input form that the wizard will generate, specifying the
properties of the page, and the bean fields that the generated Web page will
provide to the user for input:
1. Select the input fields that you want, checking the box next to each field as
seen in Figure 10-9. Modify also the title of the page, and the field labels if you
desire.
2. Click Next to continue.
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Next we design the result form, which shows the customer registration
information, that the user has entered during the registration process:
1. Design the form by specifying the page properties, like the page heading for
example. Also specify the bean fields that you want to include in the
generated Web page, as shown in Figure 10-10.
2. Click Next.
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Figure 10-10 JavaBean XML/XSL client: results form design
After finishing the design of the results form, we need to specify a prefix for all
generated files:
1. Enter the prefix for the generated files as Customer, as indicated in
Figure 10-11.
2. Click Finish.
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Figure 10-11 JavaBean XML/XSL client: prefix specification
Investigating the Web-tier generated files
It is worthwhile having a look at the files generated by the wizard to get a better
understanding of the Web tier structure. By moving to the Navigator window,
expand your Registration project, as shown in Figure 10-12 on page 228. You
may get a broken link warning on the web.xml. Rebuilding the project will resolve
this warning.
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Figure 10-12 Registration project structure after the Web tier creation
Java source files: By expanding the Java Source folder, under the
CustomerInfoWeb project, you will find two new Java files, in addition to our
original customer bean Java file. The first new file is CutomerXML.java, which is
responsible for converting a JavaBean into a DOM representation. The second
new file is CustomerXSLServlet.java, which is the controller of the whole process
as it is responsible for invoking the required business logic, and applying the XSL
to the generated DOM.
Following is a brief explanation of the contents of these two Java classes:
ꢀ CustomerXML is responsible for converting a JavaBean into a DOM
representation. Studying the code for this class, we notice the following:
– It has an attribute referencing our customer JavaBean. This attribute
represents the bean to be transformed to the DOM representation.
– It has a set of get and set methods to handle the values of the Customer
CustomerXML, sets the value for the membership attribute of the
Customer bean. This applies to all customer bean attributes. These are
– The method responsible for the transformation is produceDOMDocument.
As shown in Figure 10-13, given the JavaBean as an input to the
produceDomdocument method, the method uses Sun's jaxp (Java API for
XML processing) to produce the XML data from the JavaBean. The source
code for that method is available in Example 10-1. It creates a
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DocumentBuilder to use for the document generation. It creates a
customer element representing the document root. It adds that element to
the created document, and starts creating elements for the customer's
attributes, adding them to the document. It retrieves that values for these
attributes from the customer JavaBean, using the bean's Get methods.
After the document construction with the data, the method returns the
document.
Java Bean
produceDOM Document
JAXP
XML Data
org.w3c.dom.Document
Figure 10-13 Produce DOM Document from JavaBean
Example 10-1 Source code for CustomerXML produceDOMDocument
public Document produceDOMDocument()
throws ParserConfigurationException
{// use Sun's JAXP to create the DOM Document
DocumentBuilderFactory dbf =
DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = dbf.newDocumentBuilder();
Document doc = docBuilder.newDocument();
Element parent = null;
// create the root of the document
Element rootElement = doc.createElement("Customer");
doc.appendChild(rootElement);
addElement(doc, rootElement, "membership",
convertToString(getBean().getMembership()));
addElement(doc, rootElement, "firstName",
convertToString(getBean().getFirstName()));
addElement(doc, rootElement, "lastName",
convertToString(getBean().getLastName()));
addElement(doc, rootElement, "email",
convertToString(getBean().getEmail()));
return doc;
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}
ꢀ CustomerXSLServlet: This is responsible for applying the XSL to the DOM
generated from the CustomerXML. This process transforms and formats the
DOM information into a rendered result. This is called styling. For the styling
to be possible, two components come together: XSL Transormations (XSLT),
which allows for a reorganization of information; and XSL, which specifies the
formatting of the information for rendering. A XSL processor takes a
stylesheet consisting of a set of XSL commands, and transforms an input
XML document. Studying the code for this servlet, we noticed the following:
– The init method does the necessary configuration and initialization for the
sevlet's operation. For the servlet to handle the process of transforming
the XML data to the desirable format, based on an XSL stylesheet, the
servlet needs to do some configuration steps before invoking the XSLT
processor. The init method first creates a new instance of the
TransformerFactory class.
– Having the stylesheet XSL files present in the file system, the Transformer
factory instance needs to reference them. So the servlet creates the
template’s objects using the XSL files. A template’s object is a compiled
representation of a XSL file. Compilation of XSL is provided by JAXP.
Invoking the newTemplates method of the TransformerFactory, and
representation of that XSL file in the form of the template’s object.
– This template’s object may then be used concurrently across multiple
threads. Creating a templates object allows the TransformerFactory to do
detailed performance optimization of transformation instructions, without
penalizing runtime transformation. As shown in Example 10-2, the init
method retrieves the files using the path specifies in the begining of the
method, and creates the template’s objects using the transformer factory.
The XSLT processor should used these compiled instances of the style
sheets to transform a XML document. Exceptions are thrown if the servlet
cannot locate the XSL files in the specified location, or if the files contain
errors.
Example 10-2 Source code for CustomerXSLServlet init method
public void init(ServletConfig config)
throws ServletException
{ super.init(config);
TransformerFactory transFact =
TransformerFactory.newInstance();
String xslName = "/WEB-INF/xsl/Customer.xsl";
String xslResult = "/WEB-INF/xsl/CustomerResult.xsl";
try
{ URL stylesheetURL =
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getServletContext().getResource(xslName);
String xsltSystemID = stylesheetURL.toExternalForm();
mainStylesheet = transFact.newTemplates(
new StreamSource(xsltSystemID));
stylesheetURL = getServletContext().
getResource(xslResult);
xsltSystemID = stylesheetURL.toExternalForm();
resultStylesheet = transFact.newTemplates(
new StreamSource(xsltSystemID));
} catch (TransformerConfigurationException tce)
{ log("Unable to compile stylesheet", tce);
throw new UnavailableException(
"Unable to compile stylesheet");
} catch (MalformedURLException mue)
{ log("Unable to locate XSLT file: " + xslName);
"Unable to locate XSLT file: " + xslName);
}
– The showPage method applies a style sheet to a DOM tree. As shown in
Figure 10-14 on page 232, and in the source code in Figure 10-3 on
page 232, the method first invokes the DOM generation using the
produceDOMDocument in the CustomerXML class, mentioned in
Example 10-2 on page 230. Following the DOM generation, a new
transformer is created. This transformer applies the style sheet on the
generated DOM, and writes the transformed HTML result to the Web
browser.
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produceDOMDocument
XML Document
(resultDOM)
IN
XSL
(stylesheet)
XSLT Processor
(transformer)
HTML
OUT
Figure 10-14 ShowPage method responsible for XSL transformation
Example 10-3 Source code for CustomerXSLServlet showPage method
private void showPage(Templates stylesheet, HttpServletResponse response)throws
IOException{
try {
org.w3c.dom.Document resultDOM = getCustomerXML().produceDOMDocument();
Transformer transformer = stylesheet.newTransformer();
response.setContentType("text/html");
PrintWriter writer = response.getWriter();
transformer.transform(new DOMSource(resultDOM),
new StreamResult(writer));
} catch (Exception ex){
PrintWriter pw = response.getWriter();
pw.println("<html><body>
<h2>Transformation Error</h2><pre>");
ex.printStackTrace(pw);
pw.println("</pre></body></html>");
}
}
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– The HTTP Post method of the servlet references the CustomerXML class,
as shown in Example 10-4. It sets all the attribute values, after extracting
them from the request. After all values are set in the customer bean
present in CustomerXML, showPage is invoked.
Example 10-4 Source code for the servlet doPost method
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
CustomerXML xml = getCustomerXML();
xml.setMembership(new java.lang.Long(
request.getParameter("membership")));
xml.setFirstname(new java.lang.String(
request.getParameter("firstName")));
xml.setLastname(new java.lang.String(
request.getParameter("lastName")));
xml.setEmail(new java.lang.String(
request.getParameter("email")));
showPage(resultStylesheet, response);
}
XSL Files: By expanding the folder /Web Content/WEB-INF/xsl, under the
the xsl for the input customer data, while the CustomerResult.xsl file represents
the xsl for the data resulting from the registration process:
ꢀ Customer.xsl is the style sheet for the customer registration form. Note the
following:
– The stylesheet code in Example 10-5 represents the style and the
structure of the registration form. It is clear that it is stylesheet for an HTML
form.
Example 10-5 Part of customer stylesheet specifying the overall form structure
<xsl:template match="/">
<html>
<head>
<title>Customer Registration Form</title>
<style type="text/css">
<
text-align: center;
}
]]>
</style>
</head>
<body>
<xsl:apply-templates select="Customer"/>
</body>
</html>
</xsl:template>
– The style for the body of this form is clear in stylesheet part present in
Example 10-6. It shows that there is a heading for the body, followed by an
html form. The data is structured in table inside the form. And finally the
form has a submit button. According to the form's specification, pressing
the submit button, redirects the user to the doPost method of the
CustomerXSLSevlet.
Example 10-6 Part of registration form stylesheet focusing on form structure
<xsl:template match="Customer">
<h1>Customer Registration Form</h1>
<form action="/Registration/CustomerXSLServlet"
method="post">
<table border="0" cellpadding="2" cellspacing="0">
<xsl:apply-templates select="membership"/>
<xsl:apply-templates select="firstName"/>
<xsl:apply-templates select="lastName"/>
<xsl:apply-templates select="email"/>
</table>
<div align="center">
<hr/>
<input type="submit" name="submitBtn"
value="Submit"/>
</div>
</form>
</xsl:template>
– Each of the attribute values has got its own template for representation.
Example 10-7 shows the template for the membership attribute. Each of
the attributes has an identical template. So each attribute is included in a
table row, consisting of two columns; one for the label, and the other for
the input field.
Example 10-7 Stylesheet template for presenting the membership field
<xsl:template match="membership">
<tr>
<td>Membership: </td>
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<td><input name="membership" type="text" size="20"
maxlength="40" value="membership"/></td>
</tr>
</xsl:template>
– CustomerResult.xsl represents the stylesheet for the target HTML
representation of the retrieved customer registration information.
– The structure of the XML input data, which we can apply to this style sheet
is shown in Example 10-8.
Example 10-8 Sample structure for the input XML data to the stylesheet
<Customer>
<membership>........</membership>
<lastName>........</lastName>
<email>........</email>
</Customer>
– The structure of the target HTML format for the customer XML data is
shown in Example 10-9.
Example 10-9 Format of the target HTML representation for the customer data
<html>
<head>
<title>Customer Registration Information</title>
</head>
<body>
<h3>Customer info</h3>
<table cellspacing="0" cellpadding="2" border="0">
<tr>
<td>Membership: </td>
<td><b>........</b></td>
</tr>
<tr>
<td>First Name: </td>
<td><b>........</b></td>
</tr>
<tr>
<td>Last Name: </td>
<td><b>........</b></td>
</tr>
<tr>
<td>Email: </td>
<td><b>........</b></td>
</tr>
</table>
</body>
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</html>
– The CustomerResult.xsl needs to construct an HTML file, and it should
match that data from the XML data representation to insert it into the
HTML file. So, in the code in Example 10-10, the XSL template puts the
skeleton of the HTML document, specifying the necessary HTML tags, like
head, body, etc. In the HTML body section, the XSL file specifies another
template the matches the customer root element of the XML data. So, the
HTML body represents a customer.
Example 10-10 Sample of CustomerResult stylesheet form
<xsl:template match="/">
<html>
<head>
<title>Customer Registration Information</title>
<style type="text/css">
<![CDATA[
body
{
background-color: #f8f7cd;
}
h3
{
color: #0000ff;
text-align: center;
}
]]>
</style>
</head>
<xsl:apply-templates select="Customer"/>
</body>
</html>
</xsl:template>
– Example 10-11 shows the code for the customer template representing to
be inserted in the HTML body. First it includes a heading representing the
title of the page, then an HTML table is created for displaying the data.
The table includes four templates to be matched from the XML data, which
are the membership, firstName, lastName, and e-mail. So, the XSL
selected from the XML files the element values representing the data.
Example 10-11 Stylesheet template for customer information representation
<xsl:template match="Customer">
<h3>Customer Registration Information</h3>
<table border="0" cellpadding="2" cellspacing="0">
<xsl:apply-templates select="membership"/>
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<xsl:apply-templates select="firstName"/>
<xsl:apply-templates select="lastName"/>
<xsl:apply-templates select="email"/>
</table>
</xsl:template>
Customer.html. This file only has a link to the CustomerXSLServlet. Clicking that
link will invoke the servlet.
Schema Files: Under the same folder as the HTML file, you will find the schema
file Customer.xsd. This is the schema for the XML data representing the
customer registration information. Example 10-12 shows the contents of the
schema file. It indicates that the root element customer is a complex type. It
contains four elements; it shows their names and data types.
Example 10-12 Schema file for the XML data
<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.ibm.com" xmlns:Cu="http://www.ibm.com">
<complexType name="Customer">
<sequence>
<element name="membership" type="Cu:Long"/>
<element name="firstName" type="string"/>
<element name="lastName" type="string"/>
<element name="email" type="string"/>
</sequence>
</complexType>
<complexType name="Long">
<sequence>
</sequence>
</complexType>
</schema>
Validating the Web tier
Before we continue to the following step, we recommend that you validate the
Web tier first. The validation process is very simple. Please do is the following:
1. Righ- click on the Customer.html file, and select Run on Server option.
Choose to run the HTML file on the Websphere test environment server. This
will automatically close the XML perspective, and open the server
perspective. The Web browser will open running the HTML file. It might take
some time to start the Websphere test environment.
2. Clink on Click here to invoke the CustomerXSLServlet. The registration
form will load on the browser.
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3. Enter the customer registration information, and click Submit, as shown in
Figure 10-15.
Figure 10-15 Customer registration form
The Submit button will call the servlet, which will in turn invoke the generation of
a DOM representation of the entered data, then the result XSL will be applied on
the generated DOM, in order to get the result form showing the customer’s data,
as shown in Figure 10-16.
Figure 10-16 Result customer registration information
10.3.2 Building the entity EJB and the database schema
We are now ready to develop our back end layer, which includes the database,
and the business logic represented by the EJB, by performing the following
steps:
1. Creating an entity EJB.
2. Creating an EJB to RDB mapping.
3. Generating the database schema and table.
4. Creating an access bean.
5. Creating a JDBC data source.
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6. Binding the EJB to the JDBC data source.
EJB mapping approaches review
All of the EJB to relational mapping capabilities previously available in VisualAge
for Java are now also available in Websphere Application Developer, although
some techniques require a slightly different approach. As before, there are three
different mechanisms:
ꢀ Top down: The developer creates the CMP entity beans in the application,
and the database schema and mapping are generated from this definition.
ꢀ Bottom up: An existing database schema exists for the application, which is
imported into the development environment, and used to generate the CMP
entity beans and the mappings.
ꢀ Meet in the middle: This scenario is useful when there is a requirement to
map a series of new or existing entity beans into an existing database
schema.
For simplicity, we are using the top down approach, where we create the entity
bean, and use it to create the database schema and table definition.
Preparing to create the entity EJB
Websphere Studio Application Developer provides a wizard that facilitates the
creation of the entity EJB. Before we start using that wizard, we must perform an
important step.
Project configuration
Make sure that you create CustomerInfoEJB project and it is EJB 1.1 complient.
Switching to the J2EE perspective, and in particular J2EE view. The
CustomerInfoEJB project should appear attached to the node EJB modules.
Creating the entity EJB
To create the entity EJB using the top down approach, we do the following:
Under the EJB Modules category in the J2EE perspective, select the
CustomerInfo project, right-click, and select New—>Enterprise Bean.
The wizard for creating the Enterprise bean opens Figure 10-17. To create the
bean do the following:
1. Select Entity Bean with container-manages persistence (CMP) fields. Enter
the bean name as Customer, and the package name as registration.
2. Click Next.
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Figure 10-17 Create an Enterprise Bean wizard
Now we need to define all the CMP attributes that we need to include in the entity
bean. To do that:
1. Click the Add button, to open the window for CMP attribute creation, as
shown in Figure 10-18 on page 241.
2. Enter membership as the attribute name, and choose its type to be long.
Select the Key Field option to indicate that membership is key for that entity,
then click Apply.
3. After adding the membership, add the rest of the attributes, which are the
firstName, lastName, and e-mail. Note that these attributes are of type string,
and that you do not need to select the key field option, because these
attributes are not keys. The membership attribute is the only key for the
customer.
4. Click Finish.
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Figure 10-18 Enterprise bean details
Creating the database mapping and tables
Now that the entity bean is ready, we need to create the database mapping:
1. Under the EJB modules category, select the CustomerInfoEJB project, and
select Generate —> EJB to RDB Mapping from the menu.
The mapping wizard opens Figure 10-19 on page 242. Because we have no
existing schema currently defined in our project, Bottom Up is disabled at this
time.
2. Select Top Down.
3. Click Next.
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Figure 10-19 EJB to RBD Mapping wizard for CustomerInfo module
To define the database information on the target database information window:
1. Complete the database information as shown in Figure 10-20. Enter the
database name. In our case, we will use the same Airlinedatabase, instead
of creating a new one. You may want to create a new database for this
scenario. This is totally up to you. Select a schema name (for example,
Registration) and make sure that the Generate DDL check box is selected.
2. Click Finish.
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Figure 10-20 Target database specification
After the EJB to RDB mapping is generated, the mapping editor opens. The
editor shows the mapping between our EJB project CustomerInfoEJB, and the
Airline database, as shown in Figure 10-21. The customer entity bean is mapped
to the customer table, and so are the EJB attributes and table columns.
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Figure 10-21 EJB to RDB mapping editor
To create the customer table in the database:
1. Close the mapping editor.
2. Close the J2EE perspective, and open the data perspective. Choose the data
definition view.
3. Expand the CustomerInfoEJB project. Under the /ejbModule/META-INF, you
will find Table.ddl file.
5. Make sure that all of the script commands are selected. Click Next.
6. Select Commit changes only upon the success option.
7. Click Next.
8. Complete the database connection information as shown in Figure 10-22.
9. Click Finish to create the schema and the table.
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Figure 10-22 Database connection definition
Access beans
Access beans are Java components that adhere to the JavaBeans specification,
and are meant to simplify the development of EJB clients. An access bean
adapts an Enterprise bean to the Javanese programming model, by hiding the
home and remote interfaces from the developer. They provide fast access to
Enterprise beans by letting the developer maintain a local cache of Enterprise
bean attributes. Access beans make it possible to use an Enterprise bean in
much the same way that a JavaBean is used.
There are three types of access beans, which are listed in ascending order of
complexity:
ꢀ Data class: The simplest to use. It is designed to allow the Enterprise bean to
be used like a standard JavaBean, and it hides the Enterprise bean home and
remote interfaces from the developer.
ꢀ Copy helper: This has all the characteristics of the data class access bean,
but it also incorporates a single copy helper object that maintains a local copy
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of attributes from a remote entity bean. A program can retrieve the entity bean
attributes from the local copy helper object that resides in the access bean,
which eliminates the need to access the attributes from the remote entity
bean.
ꢀ JavaBean Wrapper: This has all the characteristics of both the data class
and the copy helper access beans. However, instead of a single copy helper
object, it contains multiple copy helper objects. Each copy helper object
corresponds to a single Enterprise bean instance.
Now that we have described access beans, we should realize that they improve
performance, because they provide the client a caching mechanism for
accessing homes. Moreover, we can use access beans in servlets and JSPs,
because they simplify coding.
Creating an access bean for the entity bean
To create the access bean for the entity EJB:
1. Close the data perspective, and open the J2EE perspective, and choose the
J2EE Hierarchy.
2. Under the EJB Modules category, select the CustomerInfo project,
right-click, and select New—>Access Bean.
The wizard for creating the Enterprise bean opens Figure 10-23. To create the
bean do the following:
1. Choose the type of the access bean to be a Data class, which will allow the
EJB to be consumed like a normal JavaBean.
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Figure 10-23 Access Bean creation wizard
2. Click Next.
3. Check to see that the EJB project selected is the CustomerInfoEJB project.
From the list of Enterprise JavaBeans, select the check box next to the
customer entity bean, and click Next.
4. Select the Enterprise bean from the list to change the default access bean
info to create data class access bean.
5. Click Finish.
In the J2EE perspective, expand the CustomerInfoEJBproject in the Navigator
view. You will find two new java classes CustomerData.java and
CustomerFactory.java under /ejbModule/registration. These two represent the
generated data class access bean.
Creating a JDBC data source
For our application to access the database, we need to create a datasource. The
data source must be defined in the application server configuration, and in our
case the application server is the Websphere Test Environment v4.0. In order to
create the data source, we need to do the following:
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1. In the server perspective and in particular in the server configuration window,
select the WebSphere administrative domain attached to the server
configurations category. Right-click and select Open from the menu to open
the editor.
2. Switch to the Data Source tab Figure 10-24.
To add a new DB2 JDBC data source:
1. Select the DB2JdbcDriver item from the list.
2. Click the Add button next to the data source list.
3. Complete the data in the dialog box (Figure 10-25.) Enter the datasource
name as RegistrationDS, and the JNDI name as jdbc/Airline, and set the
user ID and password as db2admin.
4. Set database name as AIRLINE.
5. Click OK.
6. Close the configuration editor, and save the changes.
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Figure 10-25 JDBC data source definition
Binding the EJB to a JDBC data source
Each EJB module must be assigned to a JDBC data source reference in order
for its CMP entities to persist correctly. To perform this assignment:
Customer bean. Right-click and select Open With —>Deployment
Descriptor Editor. The editor will open with the bean’s tab selected.
2. Complete the data in the section labeled DataSource Binding Figure 10-26.
Enter the JNDI name as jdbc/Airline, which matches the JNDI name for the
data source created in Figure 10-25. Enter the user ID and password as
db2admin.
3. Save the changes and close the editor.
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Figure 10-26 Defining the JDBC data source for the EJB
10.3.3 Integrating the entity EJB with the Web tier
In order to integrate the Customer EJB that we have created, with our Web tier,
we need to do the following:
1. Modify the CustomerXML(DOM) included in the Web tier, to reference the
generated CustomerEJB instead of the original Customer JavaBean.
2. Add a create method to the CustomerXML (DOM) to construct the entity bean
using the CustomerFactory. The original code uses the JavaBean constructor
to create a new Customer object. We cannot do that with the entity bean, so
we use the EJB factory’s create method.
3. Modify the CustomerXSLServlet to allow storage and retrieval of customer
data.
4. Modify the CustomerXSLServlet to invoke the create method we created.
Modifying CustomerXML
To make the CustomerXML (DOM) reference our CustomerEJB, we first need to
1. Switch to the Web perspective.
2. Right-click on the CustomerInfoWeb project. Choose the project properties
from the menu. Choose the Java Build Path, and in the Projects tab, select the
check box next to the CustomerInfoEJB project, as in Figure 10-27 on
page 251.
3. Click OK to save your changes to the project properties.
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Figure 10-27 CustomerInfoWeb project properties
You can start now on modifying the CustomerXML file, by doing the following:
ꢀ
Open the CustomerXML.javafile to start editing it. Modify the import
statements to include exactly the following:
import javax.ejb.*;
import java.rmi.*;
import registration.Customer;
import registration.CustomerFactory;
import org.w3c.dom.*;
import javax.xml.parsers.*;
ꢀ
Implement a create method that constructs a new CustomerFactory, and
invoke its create method using Customer bean’s properties, as shown in
Example 10-13.
Example 10-13 create source code
protected void create() throws
RemoteException,CreateException {
CustomerFactory factory = new CustomerFactory();
registration.Customer ejbean =
factory.create(getBean().getMembership().longValue());
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ejbean.setFirstName(getBean().getFirstName());
ejbean.setLastName(getBean().getLastName());
ejbean.setEmail(getBean().getEmail());
}
Modifying CustomerXSLServlet
The changes to the CustomerXSLServlet are in two directions. Changes to the
doPost method of the servlet that enables storing new customer records in the
database. While the changes to the doGet method of the servlet enables
retrieving customer information from the database, based on a membership input
value. To achieve our target, we need to perform the following to the
CustomerXSLServlet:
import registration.*;
import javax.ejb.*;
2. Now in the doPost method, invoke the CustomerXML create method, after
setting up all property values. You have to catch the exceptions that might be
thrown, and return to the input form. See Example 10-14.
Example 10-14 CustomerXSLServlet doPost source code
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
CustomerXML xml = getCustomerXML();
xml.setMembership(new Long(request.getParameter("membership")));
xml.setFirstName(new java.lang.String(request.getParameter("firstName")));
xml.setLastName(new java.lang.String(request.getParameter("lastName")));
xml.setEmail(new java.lang.String(request.getParameter("email")));
try{
//Write to EJB.
xml.create();
}catch(CreateException crateEx){
showPage(mainStylesheet, response);
}
showPage(resultStylesheet, response);
}
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10.3.4 Retrieval function
This registration application does not offer the retrieval function. To add the
retrieval function to CustomerXML class, we add retrieve method as
Example 10-15. This function retrieves Enterprise bean by the membership key,
then copy the properties from customer EJB to customer bean.
Example 10-15 Retrieval function
protected void retrieve(Long membership) throws RemoteException,
FinderException
{
CustomerFactory factory = new CustomerFactory();
registration.Customer ejbean = factory.findByPrimaryKey(new
CustomerKey(membership));
setFirstName(ejbean.getFirstName());
setLastName(ejbean.getLastName());
setEmail(ejbean.getEmail());
}
In the next chapter, we show how to include the retrieve function into the
registration form. At this time, we add a statement to confirm the registration. In
the doPost method, we retrieve the customer using the membership key just after
create (see Example 10-16).
Example 10-16 Confirming the creation
try{
xml.retrieve(new Long(request.getParameter("membership")));
showPage(resultStylesheet, response);
}catch(FinderException remoteEx){
}
10.4 Application deployment and testing
We are now ready to generate the deployed code to support the execution on
WebSphere test environment:
1. Switch to the J2EE Hierarchy view, select the CustomerInfoEJB under the
EJB Modules, and select Generate—>Deploy and RMIC Code.
2. Make sure that the customer entity EJB is selected, and click Finish, as in
Figure 10-28.
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Figure 10-28 Generating the deployed code for the EJB
After switching to the Navigator view, expand the CustomerInfo project, which is
the registration node under the ejbModule folder to see the deployed code.
Now that we have completed the development of the whole application, and
deployed the EJB, it is time to move to testing that application using WebSphere
Test Environment Version 4.0.
10.4.1 Testing the registration application
We need to test the registration process:
1. Switch to the server perspective, select the registration project. Select
CustomerXMLServlet, and select the option Run on Server from the menu.
The WebSphere test Environment will start, launching the browser, and
invoking the JSP in Figure 10-29.
2. Enter the necessary data, which are the membership, first name, last name,
and e-mail.
3. Click the Submit button.
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Figure 10-29 Customer Registration form
Once the Submit button is clicked, the doPost is invoked. It extracts the data
from the HTTP request, and constructs a new customer entity bean, and the data
is inserted into the database. Then the CustomerXML converts the bean into a
DOM representation. The servlet finally applies the output style sheet on the
create DOM representation creating the HTML output in Figure 10-30.
Figure 10-30 HTML resulting from the XSLT transformation
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11
Light weight XML-based
Enterprise Application
Chapter eleven provides an another approach to develop an XML based
Enterprise application without Enterprise JavaBean. Application Developer has
two libraries to query and insert/update the database. The SQLToXML library is
used to perform a query and the XMLToSQL library is used to perform an insert
or update. Both libraries work with all JDBC databases such as DB2, Oracle,
Sybase, MS-SQL Server, etc. These are useful to the simple application that
does not need to use Enterprise JavaBeans.
In this chapter, the following topics are described:
ꢀ
ꢀ
ꢀ
Architecture of light weight XML based Enterprise applications
Development of such applications using Application Developer
Deployment and testing of the solution on the Application Developer
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257
In this chapter, we replace the EJB part which is described in previous chapter
from SQL query and XML, to SQL wizard. You can use the XML from SQL wizard
to unit test your query to make sure it produces the expected result (see 6.1,
“The SQL to XML wizards” on page 102). And you should use the XML to SQL
wizard to unit test the XML document to make sure it updates the right data.
This simple architecture (illustrated in Figure 11-1) can keep the application
simple. The application server layer has been removed from J2EE architecture
and SQL <-> XML libraries will handle the database directory from Web tier
inside.
Client
Web Tier
Validation Logic
Request Handler
Servlet
SQL <-> XML
HTML/JSP
XSLT Processor
XML
Presentation
Data
Presentation Logic
Data Server
Figure 11-1 SQL<->XML solution architecture
In order to understand how these components interact with each other, have a
deep look at 11.2, “Solution outline for customer registration sample” on
page 259.
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11.2 Solution outline for customer registration sample
An overview of the sample application can be found in Chapter 8., “WebSphere
and XML approaches” on page 163. This chapter discusses the interaction
between solution components, before we progress to building the application.
There are two possible ways of interaction between the components of the
system. This difference in interaction is based on the target functionality. We
focus on the set of interactions for storing data, then we discuss the set of
interactions for retrieving customer information.
11.2.1 Customer registration
When registering, the user enters the necessary registration data in the form
provided by the HTML in the client layer. When the user presses the Submit
button, a series of interactions between system components take place, as
indicated in Figure 11-2 on page 260, and in the following steps:
1. The HTML sends the customer registration data through the HTTP request to
the servlet, invoking the servlet doPost method.
2. The servlet extracts the data from the request, and creates a new
CustomerXML object and set required properties with the extracted
registration data.
3. The servlet invokes Customer XML object’s produceDOMSource method and
get an XML document.
Tip: The XML document can be created manually using JAXP.
4. The servlet invokes XMLToSQL library.
5. XMLToSQL executes INSERT using the XML document.
6. The servlet instantiate XSLT Processor.
7. The XML document is input for the XSLT Processor.
8. The pre-designed XSL applied and result HTML has been generated and
transferred to the browser.
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259
1
2
Customer XML
(DOM)
XSL Servlet
3
6
Web
Browser
XMLToSQL
4
XML Data
XSLT
Processor
7
Customer XSL
5
8
HTML
Customer
Result XSL
DB
Figure 11-2 Customer registration scenario outline
11.2.2 Retrieving customer information
When retrieving customer data, the user enters the membership number of the
customer whose information is to be retrieved in the form provided by the HTML
in the client layer. When the user presses the Query button, a series of
interactions between system components take place, as indicated in Figure 11-3,
and in the following steps:
1. The HTML sends that value to the servlet through the HTTP request to the
servlet, invoking the servlet doPost method.
2. The servlet validates that the user has entered a membership value. Then the
servlet invokes the SQLToXML library with one parameter, membership
number.
3. The SQLToXML retrieves the data from the database and constructs an XML
document.
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Tip: Application Developer 4.0.3 contains SQLToXML library, but it returns
results as a stream data, which means you need to parse it for a document.
Later versions may have a function to get a document directly.
4. The servlet gets an XML document from SQLToXML library.
5. The servlet instantiate XSLT Processor.
6. The XML document that is the output of SQLToXML is an input for the XSLT
Processor.
7. The pre-designed XSL applied and result HTML has been generated and
transferred to the browser, so when the transformation is performed, the user
can view the retrieved customer information on the Web browser.
1
XSL Servlet
2
5
Web
Browser
SQLToXML
4
XML Data
XSLT
Processor
6
3
Customer XSL
7
HTML
Customer
Result XSL
DB
Figure 11-3 Retrieving customer data scenario outline
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11.3 Developing the customer registration sample
We are going to reuse customer registration sample code that we developed in
previous chapter. In order to develop this application, modify CustomerXSL
servlet and XSLs:
ꢀ
ꢀ
Re-generate all related files from customer bean.
Modify the CustomerXSL servlet to allow storage and retrieval of customer
data.
11.3.1 Adding the libraries to the project
You need to add two libraries to your project. Use the property window of the
project. Two variables are defined in Application Developer. To add the jars to the
classpath, use add variable button, and add XMLTOSQL and SQLTOXML. For
your information, the jars are located under the following directories:
XMLToSQL
SQLToXML
plugins\com.ibm.etools.sqltoxml_5.0.0\jars\xmltosql.jar
plugins\com.ibm.etools.sqltoxml_5.0.0\jars\sqltoxml.jar
11.3.2 XML Document format
One thing to be aware of is that the XML format is not compatible with our
customerXSL. The following XML is a sample that the libraries accept:
<SQLResult>
<Customer>
<firstname>firstname</firstname>
<lastname>lastname</lastname>
<email>email</email>
<membership>membership</membership>
</Customer>
</SQLResult>
The document root is typically SQLResult. And the first child, in this case,
Customer, is used as a table name, afterwards each column should follow
(Figure 11-6).
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XML
Document
CustomerXSL
ProduceDOMDoc..
XMLToSQL
SQLToXML
<Customer>
<firstname>
<SQLResult>
<{$TABLE-NAME}>
<{$COLUMN}>
value
IT
</firstname>
.
.
</{$COLUMN}>
.
.
</{$TABLE-NAME}>
</SQLResult>
</Customer>
Figure 11-4 Converting an XML Document
11.3.3 XMLToSQL architecture
The XMLToSQL takes one parameter to initialize. That parameter is SQLProperty
class and it contains following data:
JdbcDriver
LoginId
JDBC Driver name
Database login id
Password
JdbcServer
Schema
Database login password
Server name (ex. jdbc:db2:Airline)
Set Schema if it is different
INSERT or UPDATE
Action
db2admin.employee, db2admin is the schema.
Once the XMLToSQL is instantiate, invoke the execute method to insert or
update. XMLToSQL to connect to the database, and insert or update the data,
then disconnect from the database (Figure 11-5).
Connection pooling or datasource is not supported in this release. But
XMLToSQL has a property to set a connection. By using this property, an
application can set the connection. We will discuss how to do it later.
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SQL
Properties
-JdbcDriver
-LoginID
-Password
-JdbcServer
-Schema
-Action
Recurse
instantiate
execute
Servlet
XMLToSQL
XML Document
Figure 11-5 XMLToSQL
11.3.4 Modifying CustomerXSLServlet
The change to the CustomerXSLServlet is the doPost method of the servlet,
which enables storing new customer records in the database. Since doGet
returns the blank input form, we left as is. To achieve our target, we need to
perform the following to the CustomerXSLServlet:
ꢀ
ꢀ
Initialize XMLToSQL to work with the database.
Modify the doPost method to execute the insert.
Initializing the XMLToSQL class
We created separate initSQLProperties method to setup the property. Since we
use same property during this application running, we initialize this property in
the init method.
ꢀ
ꢀ
ꢀ
Add SqlProperties as a global variable:
private SQLProperties sqlProperties;
Add XMLToSQL as a global variable:
private XMLToSQL xml2sql;
Add initSQLProperties method (Example 11-1);
We recommend that you create a .properties file to keep the information to set
the SQLProperties.
ꢀ
In the init method, add a statement to invoke the initSQLProperties method:
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initSQLProperties();
ꢀ Also, we instantiate XMLToSQL in the init method:
xml2sql = new XMLToSQL(sqlProperties);
Example 11-1 initSQLProperties method
private void initSQLProperties()
{
sqlProperties = new SQLProperties();
sqlProperties.setJdbcDriver("COM.ibm.db2.jdbc.app.DB2Driver");
sqlProperties.setLoginId("db2admin");
sqlProperties.setPassword("db2admin");
sqlProperties.setSchema("registration");
sqlProperties.setJdbcServer("jdbc:db2:AIRLINE");
}
Creating an XML Document
We reused CustomerXSL to generate an XML Document which contains new
customer data (Figure 11-6). To do this:
1. Instantiate CustomerXSL.
2. Extract customer data from HTTPRequest.
3. Set data to CustomerXSL.
4. Get the XML Document invoking CustomerXSL’s produceDOMDocument.
instantiate
Servlet
CustomerXSL
set data
produceDOMDocument
HTTP
Request
-FirstName
-LastName
-email
XML Document
-Membership
Figure 11-6 Getting an XML Document using CustomerXSL
Modifying the produceDOMDocument method
As we mentioned, the XMLToSQL does not accept the document. XMLToSQL is
expecting the following document. Currently, CustomerXSL produces following
XML Document:
<Customer>
<firstname>firstname</firstname>
<lastname>lastname</lastname>
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<email>email</email>
<membership>membership</membership>
</Customer>
We need to add SQLResult as a root element for this document and change all
tags related to the table name or column names to CAPITAL. The easiest way is
to modify the produceDOMDocument method in the CustomerXSL class. The
following code fragment is the original code.
Element rootElement = doc.createElement("Customer");
doc.appendChild(rootElement);
We need to change to:
Element superRootElement = doc.createElement("SQLResult");
doc.appendChild(superRootElement);
Element rootElement = doc.createElement("Customer");
superRootElement.appendChild(rootElement);
We created a new produceDOMDocumentforTools method as follows.
Example 11-2 ProduceDOMDocumentforTools
public Document produceDOMDocumentforTools()
throws ParserConfigurationException
{
// use Sun's JAXP to create the DOM Document
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = dbf.newDocumentBuilder();
Document doc = docBuilder.newDocument();
Element parent = null;
//Now we need SQLResult as a root.
Element superRootElement = doc.createElement("SQLResult");
doc.appendChild(superRootElement);
Element rootElement = doc.createElement("CUSTOMER");
superRootElement.appendChild(rootElement);
addElement(doc, rootElement, "FIRSTNAME",
convertToString(getFirstName()));
addElement(doc, rootElement, "LASTNAME",
convertToString(getLastName()));
addElement(doc, rootElement, "MEMBERSHIP",
convertToString(getMembership()));
addElement(doc, rootElement, "EMAIL",
convertToString(getEmail()));
return doc;
}
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Or, you can use JAXP to change the document structure dynamically. Using
JAXP following the code fragment does this. If this document’s root element is
not SQLResult, add SQLResult and add the first child (in our case, it is
customer), to the SQLResult element. At this time, the customer element was
removed from the root and be a child of the SQLResult. Then add the SQLResult
to the document, SQLResult will be a root and customer will be a first child:
if( !(doc.getFirstChild().getNodeName().equalsIgnoreCase("SQLResult")) ){
Element rootElement = doc.createElement("SQLResult");
rootElement.appendChild(doc.getFirstChild());
doc.appendChild(rootElement);
}
datasource.
Executing the XMLToSQL class
We created doRegister method to instantiate CustomerXSL, get an XML
Document, and execute XMLToSQL in one method (Example 11-3). Since
XMLToSQL can throw an exception, we need to catch them. This sample shows if
SQLException has been thrown, the member ship already exists.
This method returns a true if it succeeds, false if it fails.
Example 11-3 CustomerXSLServlet doRegister method
private boolean doRegister(HttpServletRequest request){
CustomerXML xml = getCustomerXML();
xml.setFirstname(new java.lang.String(request.getParameter("firstname")));
xml.setLastname(new java.lang.String(request.getParameter("lastname")));
xml.setEmail(new java.lang.String(request.getParameter("email")));
xml.setMembership(new
java.lang.String(request.getParameter("membership")));
try{
xml2sql.execute(xml.produceDOMDocumentforTools(),false);
}catch(SQLException sqlexception){
System.out.println(sqlexception);
xml.setMembership("Membership is already exist");
return false;
}catch(Exception exception){
System.out.println(exception);
return false;
}
return true;
}
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Modifying the doPost method
Now we need to modify the doPost method. All we need is to invoke is the
doRegister method with HttpServletRequest. Once the doRegister succeeds, go
showpage to show results. If it fails, go back to the input form, which will be
reproduced by the doGet method. The doGet method reuses the XML Document
that is currently instantiated in the servlet instance, and the membership field has
been replaced with -1 message.
Example 11-4 CustomerXSLServlet doPost method
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
if( doRegister(request) == true){
showPage(resultStylesheet, response );
}else{
doGet(request, response);
}
}
If the membership already exists, Customer.xsl will be told as the membership is
-1. To handle this to the meaning message, we used xsl:if tag.
Example 11-5 The xsl:if tag
<td>membership
<xsl:if test = "$membr = -1" >
*
</xsl:if>
:</td>
In this case, add *next to the membership. Or, use this tag to show “Membership
is already exist” in the input field, or message area.
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HTML
XSL Servlet
Customer
Result XSL
XMLToSQL
doPost
normal case
error case
XML Data
XSLT
Processor
HTML
-Firstname
-Lastname
-email
doGet
-membership
Customer XSL
Figure 11-7 The doPost method
Adding the error case
In the error case, we need to set back the data that was originally posted from the
browser. Unless this functions, all user typed information has been cleared when
the error occurred. To bring back the data to the browser, we need to modify the
template. The original value attribute of the input tag is blank. To set back with the
value that was previously typed (the XML data contains that data), use variable
{$fname} in the value attribute. To set this variable, use xsl:variable tag and use
the value of the current position. You need this modification to all fields.
Example 11-6 Customer.XSL firstname template
<xsl:template match="firstname">
<xsl:variable name="fname">
<xsl:value-of select="."/>
</xsl:variable>
<tr>
<td>Firstname: </td>
<td><input name="firstname" type="text" size="20" maxlength="40"
value="{$fname}"/></td>
</tr>
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</xsl:template>
11.3.5 Retrieving a customer
We used SQLToXML library to retrieve a customer.
The SQLToXML takes one parameter to initialize. That parameter is the
QueryProperty class and it contains following data:
JdbcDriver
LoginId
JDBC driver name
Database login ID
Password
JdbcServer
Statement
Format
Database login password
Server name (ex. jdbc:db2:Airline)
Query statement
False
Recurse
Once the SQLToXML is instantiate, invoke the execute method to query. The
execute method takes a parameter to set a host variable. SQLToXML connects to
the database and executes a query then generates the result as an XML form
and disconnects from the database (Figure 11-8).
The host variable can be set as comma delimited. For example, to set two
variables for the following select statement, the parameter will be new
String(“Air Canada 700, Jet 787”);
SELECT * FROM PASSENGER, SCHEDULE
WHERE PASSENGER.FLIGHT = SCHEDULE.FLIGHTNO
AND PASSENGER.FLIGHT = :flight
AND SCHEDULE.AIRCRAFT = :aircraft
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Query
Properties
-JdbcDriver
-LoginID
-Password
-JdbcServer
-Statement
-Format
-Recurse
instantiate
execute
Servlet
SQLToXML
XML Document
Figure 11-8 SQLToXML
Initializing the SQLToXML class
we use same property during this application running, we initialize this property
in the init method.
ꢀ Add QueryProperties as a global variable:
private QueryProperties queryProperties;
ꢀ Add initQueryProperties method (Example 11-7).
ꢀ In the init method, add a statement to invoke the initQueryProperties method.
initQueryProperties();
ꢀ Also, we instantiated SQLToXML in the init method:
sql2xml = new SQLToXML(queryProperties);
Example 11-7 initQueryProperties method
private void initQueryProperties()
{
queryProperties = new QueryProperties();
queryProperties.setJdbcDriver(
"COM.ibm.db2.jdbc.app.DB2Driver");
queryProperties.setLoginId("db2admin");
queryProperties.setPassword("db2admin");
queryProperties.setJdbcServer("jdbc:db2:AIRLINE");
queryProperties.setStatement(
"SELECT * FROM CUSTOMER WHERE SERIAL = :membership");
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queryProperties.setFormat("GENERATE_AS_ELEMENTS");
queryProperties.setRecurse(false);
}
Executing the SQLToXML class
We created the doQuery method to execute the query and get an XML
Document as a result (Example 11-8). SQLToXML returns XML data as a stream,
and it only accepts an instance of PrintWriter. To get it as a string data, you need
to create an instance of StringWriter, then create an instance of PrintWriter from
the StringWriter.
Tip: A future release of Application Developer contains a method to get a
document. We tested this method and it works. When it is available, you can
get a document directory from SQLToXML.
Example 11-8 CustomerXSLServlet doQuery method
//For Application Developer 4.0.3
private StringWriter doQuery(HttpServletRequest request){
StringWriter xmldata = new StringWriter();
PrintWriter xmlwr = new PrintWriter(xmldata);
try{
sql2xml.execute(new java.lang.String(
request.getParameter("memberhsip")),xmlwr,null,null,null);
}catch(Exception exception){
System.out.println(exception);
}
return xmlData;
}
//For Application Developer 5.0
private org.w3c.dom.Document doQuery(HttpServletRequest request){
StringWriter xmldata = new StringWriter();
PrintWriter xmlwr = new PrintWriter(xmldata);
try{
sql2xml.setParameters(new java.lang.String(
request.getParameter("memberhsip")));
sql2xml.execute();
}catch(Exception exception){
System.out.println(exception);
}
return sql2xml.getDocument();
}
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Modifying the doPost method
Now we need to modify the doPost method. All we need to do is invoke the
doQuery method with HttpServletRequest. We are reusing same form with
registration, we need to add another button to query. We define the button as
queryBtn, and check in the doPost method. If queryBtn is pressed, doPost
proceeds to doQuery and shows. Once the doQuery succeeds, go showpage to
show results. If it fail, go back to the input form which will be reproduced by doGet
method. The doGet method reuses the XML Document that is currently
instantiated in the servlet instance, and the membership field has been replaced
with -1, which is the Membership already existedmessage.
Example 11-9 CustomerXSLServlet doPost method for query
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
if( request.getParameter("queryBtn") != null ){
showPage(resultStylesheet, response, doQuery(request));
}else{
if( doRegister(request) == true){
showPage(resultStylesheet, response, doQuery(request));
}else{
doGet(request, response);
}
} }
Modifying the showPage method
The showPage method takes an output document as the third parameter. The
parameter is org.w3c.dom.Document type, so to run under Application Developer
4.0.3, you need to use following statement:
transformer.transform(new StreamSource(
new StringReader(resultdata)), new StreamResult(writer));
Example 11-10 showPage method
private void showPage(Templates stylesheet, HttpServletResponse response,
org.w3c.dom.Document doc)
throws IOException
{
try
{
Transformer transformer = stylesheet.newTransformer();
response.setContentType("text/html");
PrintWriter writer = response.getWriter();
transformer.transform(new DOMSource(doc), new StreamResult(writer));
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}
catch (Exception ex)
{
PrintWriter pw = response.getWriter();
pw.println("<html><body><h2>Transformation Error</h2><pre>");
ex.printStackTrace(pw);
pw.println("</pre></body></html>");
}
}
Modifying the doGet method
Regarding the above modification, doGet must be changed to set document.
Example 11-11 showPage method
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
try{
showPage(mainStylesheet, response,
getCustomerXML().produceDOMDocument());
}catch(Exception e){
System.out.println(e);
}
}
Modifying the XSL file
Since our main HTML is a dynamic thing, we can modify the transformation file to
add Query Button to the main form (Figure 11-9). Open Customer.xsl file and
look for membership template (Example 11-12).
Example 11-12 Customer.XSL membership template
<xsl:template match="membership">
<xsl:variable name="num">
<xsl:value-of select="."/>
</xsl:variable>
<tr>
<td>Membership: </td>
<td><input name="memberhsip" type="text" size="20" maxlength="40"
value="{$num}"/>
<input type="submit" name="queryBtn" value="Query"/>
</td>
</tr>
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</xsl:template>
Also, result XSL needs a modification. As we mentioned about the SQLResult
element, the result document’s root is also SQLResult. You need to modify the
result XSL to match the document, and all returned tags are capitalized as we
mentioned. Complete Result XSL is as follows (Figure 11-13).
Example 11-13 Result XSL
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns="http://www.w3.org/1999/xhtml">
<xsl:output method="xml" indent="yes" encoding="UTF-8"
doctype-public="-//W3C//DTD XHTML 1.0 Transitional//EN"
doctype-system="http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"/>
<xsl:template match="/SQLResult|/">
<html>
<head>
<title>Registration Result</title>
<style type="text/css">
<![CDATA[
body
{
background-color: #ffffff;
}
h3
{
color: #0000ff;
text-align: center;
}
]]>
</style>
</head>
<body>
<xsl:apply-templates select="CUSTOMER"/>
</body>
</html>
</xsl:template>
<xsl:template match="Customer|CUSTOMER">
<h3>Registration Result</h3>
<table border="0" cellpadding="2" cellspacing="0">
<xsl:apply-templates select="firstName|FIRSTNAME"/>
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<xsl:apply-templates select="lastName|LASTNAME"/>
<xsl:apply-templates select="membership|MEMBERHSIP"/>
<xsl:apply-templates select="email|EMAIL"/>
</table>
</xsl:template>
<xsl:template match="firstName|FIRSTNAME">
<tr>
<td>firstName: </td>
<td><b><xsl:value-of select="."/></b></td>
</tr>
</xsl:template>
<xsl:template match="lastName|LASTNAME">
<tr>
<td>lastName: </td>
<td><b><xsl:value-of select="."/></b></td>
</tr>
</xsl:template>
<xsl:template match="membership|MEMBERSHIP">
<tr>
<td>membership: </td>
<td><b><xsl:value-of select="."/></b></td>
</tr>
</xsl:template>
<xsl:template match="email|EMAIL">
<tr>
<td>email: </td>
<td><b><xsl:value-of select="."/></b></td>
</tr>
</xsl:template>
</xsl:stylesheet>
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Bring back
the data
Query
Button
Figure 11-9 Customer Registration form
11.3.6 Using datasource with SQLToXML and XMLToSQL class
not designed to accept the datasource. To use with datasource and the
connection pooling, we can use set/getConnection methods, and once the
connection has been set to the class, it will not try to connect to the database
itself. So, we extended both classes to support the datasource. The new classes
inherit the original class, so new classes can use all functions of the originals
(Figure 11-10).
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277
J2EE
SQLToXMLds
Query
Properties
-JdbcDriver
-LoginID
-Passw ord
-JdbcServer
-Schem a
JNDI
Data so urc e
Connection
Pooling
-Action
-Recurse
SQLToXM L
Application
DB
XMLToSQLds
XM LToSQL
SQL
Properties
-JdbcDriver
-LoginID
-Passw ord
-JdbcServer
-Statem ent
-Form at
Document
reformat
Datasource
-Recurse
Figure 11-10 SQLToXMLds and XMLToSQLds
Tip: You need to add naming.jar from runtime library under
runtime/base_v5/lib.
Class definition
Both SQLToXMLds and XMLToSQLds extend SQLToXML and XMLToXML. Each
class has a global variable to keep the datasource. The following code fragment
shows the class definition:
public class XMLToSQLds extends XMLToSQL{
private DataSource datasource;
}
public class SQLToXMLplus extends SQLToXML{
private DataSource datasource;
}
Getting the datasource
We add to methods to set datasource. We used two approaches to get the
datasource.
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Example 11-14 setDatasourceMethods
/**
* Setting up datasource
* @param dsname String.
* @param dsclassname String DataSource class name
ex.COM.ibm.db2.jdbc.DB2ConnectionPoolDataSource.
* @exception CMFactoryException
* @exception ClassNotFoundException
*/
public void setDataSource(String dsname, String dsclassname)
throws CMFactoryException,
ClassNotFoundException
{
java.util.Properties prop = new java.util.Properties();
prop.put(DataSourceFactory.NAME, dsname);
prop.put(DataSourceFactory.DATASOURCE_CLASS_NAME,dsclassname);
datasource = DataSourceFactory.getDataSource(prop);
}
/**
* Setting up datasource
* @param dsname String.
* @exception javax.naming.NamingException
*/
public void setDataSource(String dsname)
throws NamingException
{
java.util.Properties prop = new java.util.Properties();
prop.put(Context.INITIAL_CONTEXT_FACTORY,
"com.ibm.websphere.naming.WsnInitialContextFactory");
Context ctx = new javax.naming.InitialContext(prop);
datasource = (DataSource)ctx.lookup(dsname);
}
Constructors
New constructors have a second parameter to set the datasouce. It accepts the
datasource itself or the datasource name.
Example 11-15 setDatasourceMethods
/**
* Constructor for SQLToXMLds.
*/
public SQLToXMLds(QueryProperties qprop, DataSource ds) {
super(qprop);
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279
datasource = ds;
}
/**
* Constructor for SQLToXMLds.
*/
public SQLToXMLds(QueryProperties qprop, String dsname) {
super(qprop);
try{
setDataSource(dsname);
}catch(NamingException e){
System.out.println(e);
}
}
Execute methods
All execute methods are overridden and try to get a connection through the
datasource:
public void execute(String s0, String s1, String s2, String s3) throws
Exception{
setConnection();
super.execute(s0,s1,s2,s3);
}
private void setConnection() throws SQLException{
if(datasource != null ){
super.setConnection(datasource.getConnection());
}
}
Once you created the code, modify your servlet to use the SQLToXMLds,
XMLToSQLds instead of SQLToXML and XMLToSQL. You need to define the
datasource in the WebSphere Test Environment setting, and need to add the
datasource name where you are invoking the constructor of them. Now you can
use datasource. You still need to set the QueryProperties or SQLProperties, jdbc
driver name, loginid, password, and jdbcservernames are no longer needed.
SQLResult is also resolved in the execute method of XMLToSQLds class. The
overrided execute class is doing this function as follows:
public void execute(Document doc, boolean continueOnSQLError)
throws SQLException,
// connection creation failed
ClassNotFoundException, // jdbc driver is missing
IOException,
SAXException,
// invalid input stream
// parse error
ParserConfigurationException
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{
if(datasource != null ){
super.setConnection(datasource.getConnection());
}
if( !(doc.getFirstChild().getNodeName().equalsIgnoreCase("SQLResult"))
){
Element rootElement = doc.createElement("SQLResult");
rootElement.appendChild(doc.getFirstChild());
doc.appendChild(rootElement);
}
super.execute(doc,continueOnSQLError);
}
If this Document’s root element is not SQLResult, add SQLResult, and add the
first child (in our case, it is customer), to the SQLResult element. At this time, the
customer element was removed from the root and is a child of the SQLResult.
Then add the SQLResult to the document, SQLResult will be a root, and
customer will be a first child.
11.3.7 Conclusion
SQLToXML and XMLToSQL can be the XML front end of the database. Using
these libraries, we can use the XML data as the core data of the application
(Figure 11-11).
Servlet
Browser
XML
Data
SQLToXML
XMLToSQL
XSLT Processor
DB
Figure 11-11 Core data is an XML
You have seen how to use Application Developer to:
ꢀ Update the database with dynamically generated XML within a servlet using
XMLToSQL class library.
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ꢀ Dynamically generate XML from SQL queries at run time using the
SQLToXML class library within a servlet.
ꢀ How to use the datasource and the connection pooling within XMLToSQL and
SQLToXML libraries within a servlet.
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12
Deploying your Web
application
Deployment of a Web application can be done manually or automatically using
Application Developer.
This chapter describes the following:
ꢀ Manual deployment:
– Exporting your EAR from Application Developer
– Installing the EAR file on WebSphere AEs
– Starting the WebSphere AEs admin GUI
– Installing the EAR on WebSphere AEs
– Configuring your server
– Testing the application
ꢀ Automatic deployment to a remote server:
– Creating a remote server instance
– Publishing to remote server
– Testing the application
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12.1 Manual deployment
This section explains how to deploy the application manually to WebSphere AEs.
Complete the following steps to export an EAR file:
1. From the File menu, select Export.
2. Select the EAR file export wizard and click Next.
The window as shown in Figure 12-1 will appear.
Figure 12-1 Exporting a project EAR file
In this window you can select the EAR project that you want to export, as well as
select the location where you want to export.
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You can further specify additional options as appropriate using the options check
boxes. To export the source files, select the Export source files check box. If
you are exporting to an existing file, and you do not want to be warned about
overwriting it, select the Overwrite existing files without warning check box.
Click Finish.
12.1.2 Installing the EAR file on WebSphere AEs
This topic discusses how to install the EAR file on WebSphere.
After exporting the EAR file, FTP or copy the EAR file to the
../WebSphere/AppServer/installableApps directory in the WebSphere AEs
product directory structure.
The EAR file can be installed by either using the WebSphere Admin Console or
manually with the command line option SEAppInstall. An example of manual
installation for the registration would be:
SEAppInstall -install ../installableApps/Registration.ear
12.1.3 Starting the WebSphere AEs Admin Console
Start the application admin server by selecting Start—>Programs—>IBM
WebSphere Application Server V4.0 AES—>Start Admin Server, on a
Windows machine, or use the startServer.sh script on a UNIX machine.
The server is started when the following message is shown in the console:
SPL0057I: The server Default Server is open for e-business.
Please review the server log files for additional information.
Standard output: C:\WebSphere\AppServer/logs/default_server_stdout.log
Standard error: C:\WebSphere\AppServer/logs/default_server_stderr.log
Once you have started the Application Server, start the administrator’s console
by one of the two methods. Select Start—>Programs—>IBM WebSphere
Application Server V4.0 AES—>Administrator’s Console, on a Windows NT
machine, or by accessing it from a browser by typing:
http://localhost:9090/admin/
Enter a user ID in the window, and click the Submit button.
Note: This user ID does not need to be a valid user ID on the system. It is only
used only for tracking user-specific changes to the configuration data.
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12.1.4 Installing the EAR
This topic discusses how to install an EAR file in WebSphere AEs using the
admin console. During this task, you will install the application files (.ear, .jar, and
.war).
To install an application:
1. Expand the tree on the left side of the console to locate
Nodes—>hostname—>Enterprise Applications.
2. Select Enterprise Applications.
The right side of the console should display the list of zero or more installed
applications (as .ear files).
3. Click the Install button displayed on the right side of the console, above the
list of installed applications.
Here you need to specify the location of the application or module, referring to
the application property reference as needed to fill in the field values, and the
application name.
Note: Use the first set of fields if the console and application files are on
the same machine (whether or not the server is on that machine, too). Use
the second set of fields (including remote path) if the application files
already reside on the same machine as the server, and the console is
being run from a remote machine. See the field help for further discussion
of the remote file path.
4. Click Next.
5. On the next page select Virtual Host Name.
Follow the instructions on the resulting Task wizard. Depending on the
components in your application, various panels will be displayed:
– Modify Role to User Mapping (valid for all applications).
– Modify EJB Run as Role to User Mapping (valid for applications
containing EJB modules with one or more entity beans that use the IBM
deployment descriptor extension for Run As Settings, Run As Mode, Run
As Specified Identity).
– Modify EJB to JNDI Name Mapping(valid for applications containing EJB
modules).
– Modify EJB Reference to JNDI Name Mapping (valid for applications
containing EJB modules with EJB references in their deployment
descriptors).
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– Modify Resource Reference to JNDI Name Mapping (valid for applications
containing Web modules with resource references in their deployment
descriptors).
– Specify Virtual Host Mapping (valid for applications containing Web
modules) and includes JSP precompilation option.
– Specify CMP Data Source Binding(valid for applications containing EJB
modules with container managed entity beans).
6. Click Finish when you have completed the wizard.
Note: Be patient if the application you are installing contains EJB modules
for which code must be generated for deployment. This step can take a
while.
7. Verify that the new application is displayed in the tree on the left side of the
console. It should be located at Nodes—>hostname—>Enterprise
Applications.
8. To save your configuration click the Save button.
9. Select the application and click the Start button.
10.(Optional) To have the configuration take effect:
– Stop the application server.
– Start the application server again.
– Stop the HTTP Web server.
– Start the HTTP Web server again.
Note: If you installed an application while the server was running, the
newly installed application and its modules can be viewed in the list of
installed Enterprise applications, from which applications and their
modules can be started, stopped, and restarted. However, the
application and modules will remain in a cannot be runstate until the
server is stopped and started again.
12.1.5 Testing the application
You can now test your application on the remote WebSphere Application Server.
To do so, start the Sample application start page (index) by typing
http://localhost:9080/Registration/ in your browser.
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12.2 Publishing to a remote server (AEs)
Prerequisites: With Application Developer, you can deploy the application to a
remote server using a remote server instance and configuration. If you want to
publish your projects remotely on WebSphere Application Server AEs, you must
install the following applications on the remote server:
ꢀ IBM WebSphere Application Server Advanced Single Server Edition for
multiplatforms
ꢀ IBM Agent Controller
ꢀ (Optional) FTP server
Important: Ensure the IBM Agent Controller is running on the remote
server and is inside a firewall.
Tip: In a team environment, care must be taken when publishing code to a
remote server. Make sure the members of the team do not step on each
other when deploying. It is a good idea to assign the deployment process to
a lead developer to ensure correct code versions are deployed. This
document does not define the details of the application build process.
12.2.1 Creating a remote server instance
1. From the Server view of the server perspective, create the server
configuration for the remote WebSphere AEs Server. Select New—>Server
Instance or New—>Server Instance and configuration.
On the first page of the Create a New Server Instance wizard or the Create a
New Server Instance and Server Configuration wizard (Figure 12-2):
– In the Server Name field, type a name for the new server.
– In the Folder field, enter a folder name for the server.
2. Select WebSphere Remote Server as the instance type. The Next button is
enabled allowing you to specify additional remote server information needed
to transfer files remotely.
3. Click Next.
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Figure 12-2 Creating a remote server instance
4. The second page of the server creation wizard opens allowing you to provide
additional remote server instance information required for using the
WebSphere Application Server remotely (Figure 12-3).
Note: All paths on this page are seen from the remote machine.
– In the Host address field, type the fully qualified DNS name or the IP
address of the remote machine that WebSphere Application Server is
running on. The field is pre-filled with the default address for the local host
(127.0.0.1).
Tip: For more information about any of the fields on this and other
wizards, select the field and then press F1.
– In the WebSphere installation directory field, type the path where you
installed WebSphere Application Server on the remote machine. This path
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is the same as the WAS_ROOT path mappings as defined by the
WebSphere server configuration.
If you have installed WebSphere Application Server in the default directory,
use c:/WebSphere/AppServerdirectory as the WebSphere installation path.
If you select the Use default WebSphere deployment directorycheck box, then
you want to use the default WebSphere deployment directory. The WebSphere
deployment directory field is then pre-filled with the default value. Otherwise, in
the WebSphere deployment directory field, type the path of the directory where
the Web application and server configurations will be published. This directory is
any existing directory that can be seen from the remote server machine.
If the directory E:/testdir resides on the remote machine, then type E:/testdirin
this field.
If you are following WebSphere naming conventions and install WebSphere
Application Server in the C:/WebSphere/AppServer directory, then the
WebSphere deployment directory is C:/WebSphere/AppServer.
Note: When publishing to the remote server, the server configuration and the
Web application will be published to a directory under the remote deployment
directory called config and installedApps respectively.
If you select the Use default WebSphere deployment directory check box when
creating a remote server instance, and then publish using this instance, the
default WebSphere Application Server server-cfg.xml file and plugin-cfg.xml files
are replaced with the published version
Optional: In the DB2 driver location field, type the DB2 location where the DB2
classes reside in the remote machine. If the default value is set in the Preference
WebSphere page, this field is pre-filled with the DB2 location.
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Figure 12-3 Remote server instance settings
5. Click Next again to display the third page of the server creation wizard.
This page allows you define a remote file transfer instance. A remote file transfer
instance contains information for transferring Web applications and server
configurations to the remote server during publishing (Figure 12-4).
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Figure 12-4 Remote file transfer option
6. Select one of the following radio buttons:
– Create a new remote file transfer instance, defines a new set of
parameters and environment settings needed to transfer files remotely.
– Use an existing remote file transfer instance, lists the already defined
remote file transfer instances that you can use for transferring files
remotely.
7. If Create a new remote file transfer instance radio button is selected:
– From the list, select one of the following:
•
Copy file transfer mechanism, to copy resources directly from one
machine to another in the file system.
•
FTP file transfer mechanism, to copy resources from one machine to
another using File Transfer Protocol (FTP).
8. Click Next to display the fourth page of the server creation wizard.
If Use an existing remote file transfer instance radio button is selected, the
Next button is not enabled (Figure 12-5).
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– Select the remote file transfer instance that you want to use to transfer files
remotely. Omit the next step.
If Copy file transfer mechanism is selected, the next page of the wizard
appears (Figure 12-5).
– In the Project folder field, type the name of the project folder where the
remote file transfer instance will reside.
– In the Remote file transfer name field, type the name of the remote file
transfer instance.
Note: For more information about any of the fields on this and other
wizards, select the field, and then press F1.
Figure 12-5 Remote copy options
ꢀ In the Remote target directory field, type the remote target directory where
you want your applications and server configuration published. This remote
target directory is the one seen by the local machine. If WebSphere
Application Server is installed on a different machine, then the remote target
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directory is the network drive that maps to the WebSphere deployment
directory. If WebSphere Application Server is installed on the same machine
as the workbench, then the remote target directory should be the same as the
contents in the WebSphere deployment directory field.
If the remote Server is on the local machine, then C:/WebSphere/AppServer
is the directory. If the remote Server is on a remote machine, then we use the
mapped drive name for the shared directory (mapped as L:/ in our example).
The Next button is enabled only if you are creating a new server instance and
server configuration together.
9. Click Next if you want to change the HTTP port number.
10.Click Finish to create a remote file transfer instance and a remote server
instance. These instances will reside locally on your machine. The server
instances appear in the Server Configuration view. The remote file transfer
instances appears in the Navigator view.
If FTP file transfer mechanism is selected, the next page of the wizard
appears.
– In the Project folder field, type the name of the project folder where the
remote file transfer instance will reside.
– In the Remote file transfer name field, type the name of the remote file
transfer instance.
– In the Remote target directory field, type the remote target directory where
you want your application and server configuration published. This remote
target directory points to the WebSphere deployment directory that is seen
from the workbench using the FTP client program.
If the WebSphere deployment directory is C:/WebSphere/AppServer and
your FTP server route directory is C:/, then your remote target directory is
/WebSphere/AppServer.
Note: To determine whether a beginning slash is required, log on to the
FTP server using a FTP client program, and then type the pwd
command. If the results containing the default log on directory begins
with a slash, then a slash is required prior to typing the remote target
directory in the Remote target directory field.
– In the FTP URL field, type the URL that is used to access the FTP server.
– In the User login field and the User password field, type the FTP user ID
and password, which will be used to access the FTP server.
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– In the Connection timeout field, type the time (in milliseconds) that the
workbench will wait this long while attempting to contact the FTP server
before timing out.
– Select the Use PASV Mode (Passive Mode) to go through the firewall
check box, if you want to pass through a firewall provided that one is
installed between your FTP server and the workbench.
– Select the Use Firewall check box, if you want to use the firewall options.
– To change the firewall options, select the Use Firewall check box, and
then click Firewall Settings.
– The Next button is enabled only if you are creating a new server instance
and server configuration together. Click Next if you want to change the
HTTP port number.
11.Click Finish to create a remote file transfer instance and a remote server
instance. These instances will reside locally on your machine. The server
instances appear in the Server Configuration view. The remote file transfer
instances appears in the Navigator view.
12.Add the project to the new server configuration.
13.Make sure the project is removed from the other server configurations.
12.2.2 Publishing to remote server
1. Select Run On Server from the context menu of Application Entry view of the
server perspective.
On the remote machine you will see the new directory added to the installedApps
directory.
12.2.3 Testing the application
You can now test your application on the remote WebSphere Application Server.
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A
Installing WebSphere Studio
Application Developer
In this appendix we describe how to install WebSphere Studio Application
Developer. The installation instructions specifically apply to Version 5, but should
be very similar for more recent versions of the product.
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Things to do before installation
Before you proceed with installation, please verify that your hardware and
software configuration meets the following prerequisites:
ꢀ Windows 2000, Windows ME, Windows 98, or Windows NT 4.0 with Service
Pack 6a or higher
ꢀ Microsoft Internet Explorer 5.5 or higher
ꢀ TCP/IP installed and configured
ꢀ A mouse or alternative pointing device
ꢀ Pentium II processor or higher recommended
ꢀ SVGA (800x600) display or higher (1024x768 recommended)
ꢀ 256 MB RAM minimum (512 MB recommended)
ꢀ A minimum of 400 MB free disk space based on NTFS. Actual disk space on
FAT depends on hard disk size and partitioning
Also please check the following before beginning the install:
ꢀ In addition to the disk space requirements for the product, you need to have
at least 50 MB of space available on your Windows system drive and the TMP
or TEMP environment variable must be pointing to a directory with at least 10
MB free.
ꢀ If you have the IBM HTTP Server or WebSphere Application Server running,
they need to be shut down.
ꢀ The Services window should not be open. If it is, the Remote Agent Controller
cannot be installed.
Note: If you have VisualAge for Java or any version of WebSphere Studio
already installed, there is no need to un-install before installing Application
Developer.
Installing Application Developer
Start the installation by inserting IBM WebSphere Studio Application Developer
Early Availability Version 5 CD-ROM, then select Install IBM WebSphere Studio
Application Developer (Figure 12-6) or running SETUP.EXE from the directory
IBM_WS_Application_Developer.
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Figure 12-6 WebSphere Studio Application Developer installation
After the first couple of panels where you have to accept license information and
choose a directory where to install Application Developer, you will be promoted
to select installation components (Figure 12-7).
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Figure 12-7 Select options
On this page you select what components you will use. Options are, plug-in
development samples and ClearCase plug-in. Select options, depends on your
needs.
Selecting your workspace
You need to create your workspace when you launch Application Developer
(Figure 12-8). By clicking the check box, the workspace will be the default.
Figure 12-8 Creating the Workspace
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Verifying the installation
Once the installation program has run, click the Windows Start button and select
Programs—>IBM WebSphere Studio Application Developer—>IBM
WebSphere Studio Application Developer.
If the installation has worked correctly, you should see your default (J2EE)
perspective with the Application Developer welcome page (Figure 12-9).
Figure 12-9 Application Developer J2EE perspective (welcome)
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Things to do before installation
Prior to installing AEs, the following checks and tasks need to be completed on
the WebSphere Server machine:
1. Check hardware and software prerequisites.
2. Create groups and users.
3. Check that IP ports are unused.
4. Stop the Web server processes.
Hardware and software prerequisites
AEs has the following hardware and software requirements:
ꢀ Hardware:
– 180 MB diskspace (minimum) for AEs
– 50 MB diskspace (minimum) for IBM HTTP Server
– 135 MB diskspace (minimum) for TEMP directory
– 500Mhz Pentium III or above
– 384 MB RAM minimum, 512 MB recommended
– Ethernet or token ring card
– CD-ROM drive
– Network connectivity to the Internet
ꢀ Software:
– Microsoft Windows 2000 Server, SP 1 or 2 or Microsoft Windows NT
Server 4.0 SP 6a
– IBM HTTP Server 1.3.19
(IBM HTTP Server is included with AEs and will be installed if not already
present.)
Create groups and users
To create the required groups and users, perform the following steps:
1. If you have not already done so, create a Windows 2000 user under which the
WebSphere service will be run, as follows:
– Locally defined (not a member of a Windows domain)
– Member of administrators group.
You can create local users and assign group memberships by clicking
Control Panel—>Administrative Tools—>Computer Management
—>System Tools —>Local Users and Groups.
2. Assign the following rights to this user:
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– Act as part of the Operating System
– log on as a service
You can assign user rights by clicking Control Panel—> Administrative
Tools —>Local Security Policy—>Local Policies—>User Rights
Assignment.
Tip: We suggest creating the user wsadmin.
Check that IP ports are unused
To check that the required ports are not in use, perform the following steps:
1. Check that there are no existing active services that use the following IP ports
on the server:
– 900 (bootstrap port)
– 9000 (location service daemon)
– 9080 (default application server).
Use the following command for this task: C:\> netstat -an
Stop the Web server processes
The IBM HTTP Server process must be stopped while AEs is being installed.
The installation changes the httpd.conf configuration file as part of the Web
server plug-in component installation.
ꢀ Issue the command: C:\> net stop "IBM HTTP Server" or stop the service
under Control Panel—>Administrative Tools—>Services.
Install WebSphere Application Server
To install AEs using the GUI installer interface, complete the following steps on
the WebSphere server machine:
Tip: The WebSphere installer (setup.exe) also provides a non-GUI, scripted or
silent mode of operation. See product documentation for details.
1. Log on with a user ID that has administrator rights to the local server domain.
2. Insert the AEs CD.
3. Start the AEs installation by double-clicking Setup from the root of the CD.
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4. In the Choose Setup Language window, select your national language from
the drop-down menu (English is selected by default) and click OK.
5. In the WebSphere Application Server Attention window, read the warnings
and then click Next to continue.
6. In the Installation Options window shown in Figure 12-10, select Typical
Installation, and then click Next. If you have some special requirements, you
may want to select Custom Installation instead. This will give you the option
to deselect certain options, for example, the IBM HTTP Server and the JDK.
Figure 12-10 Installation options
7. In the Security Options window (shown in Figure 12-11) enter the user name
and password of the Windows account under which AEs is to run as a
service. This is the account created during the WebSphere pre-installation
tasks. Click Next to continue.
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Figure 12-11 Security options
8. In the Product Directory window, select the destination directory, then click
Next.
9. In the Select Program Folder window, accept the default and click Next.
10.. In the Install Options Selected window, note the selected options and click
Next to start the installation.
11.When the Setup Complete window is shown, click Finish.
12.. In the Restarting Windows window, select to restart the computer to
complete the installation.
Verifying the installation
Perform the following tasks to verify that the installation was successful:
1. Start the WebSphere administrative server processes.
2. Start WebSphere default server.
Start the WebSphere administrative server processes: The WebSphere
administrative server needs to be started in order to test the installation:
1. Start the server by selecting Start application server from the WebSphere
menu or by entering C:\WebSphere\AppServer\bin\startServer.bat on a
command line.
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2. The startup of WebSphere administrative server was successful if the last line
of the <WAS_HOME>\logs\default_server_stdout.log file is similar to the
following:
[02.04.05 15:48:56:309 PST] 5dc79b14 Server A WSVR0023I: Server Default
Server open for e-business
configured by accessing its servlets through the Web server embedded within
the WebSphere V4.0 Web container:
a. Using a Web browser, request the following URL:
http://localhost:9080/servlet/snoop
A window similar to the one shown in Figure 12-12 should be displayed in
your browser.
Figure 12-12 Snoop servlet accessed through embedded Web server
WebSphere Application Server AEs has now been successfully installed on your
workstation.
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C
Additional material
This redbook refers to additional material that can be downloaded from the
Internet as described below.
Locating the Web material
The Web material associated with this redbook is available in softcopy on the
Internet from the IBM Redbooks Web server. Point your Web browser to:
Alternatively, you can go to the IBM Redbooks Web site at:
Select the Additional materials and open the directory that corresponds with
the redbook form number, SG24-6586.
Using the Web material
The additional Web material that accompanies this redbook includes the
following file:
File name
Description
SG246586.zip
Zipped code samples
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System requirements for downloading the Web material
The following system configuration is recommended:
Hard disk space:
5 MB minimum
Operating System: Windows
Processor:
Memory:
Pentium II or higher
256 MB above
How to use the Web material
Create a subdirectory (folder) on your workstation, and unzip the contents of the
Web material zip file into this folder.
Each sub directory has a code to use the chapters:
workspace
Web services sample in Chapter 9
workspaceEJB
workspaceLW
EJB sample in Chapter 10
SQL to/from XML and DataSource sample in Chapter 11
Each directory is an image of workspace. You can look using explorer or import
each project using project import function.
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Abbreviations and acronyms
AAT
ACL
API
application assembly tool
access control list
HTTP
IBM
Hypertext Transfer Protocol
International Business
Machines Corporation
application programming
interface
IDE
integrated development
environment
BLOB
BMP
CCF
binary large object
IDL
Interface Definition Language
Internet Inter-ORB Protocol
bean-managed persistence
IIOP
IMS
Common Connector
Framework
Information Management
System
CICS
Customer Information Control
System
ITSO
International Technical
Support Organization
CMP
container-managed
persistence
J2EE
J2SE
JAF
Java 2 Enterprise Edition
Java 2 Standard Edition
Java Activation Framework
Java archive
CORBA
DBMS
DCOM
Component Object Request
Broker Architecture
database management
system
JAR
JDBC
JDK
JFC
Java Database Connectivity
Java Developer’s Kit
Distributed Component
Object Model
Java Foundation Classes
Java Messaging Service
DDL
DLL
DML
DOM
DTD
EAB
EAI
data definition language
dynamic link library
JMS
JNDI
Java Naming and Directory
Interface
data manipulation language
document object model
document type description
Enterprise Access Builder
JSDK
JSP
Java Servlet Development Kit
Java server page
JTA
Java Transaction API
Java Transaction Service
Java Virtual Machine
Enterprise Application
Registration
JTS
JVM
LDAP
EAR
EIS
Enterprise archive
Lightweight Directory Access
Protocol
Enterprise Information
System
MFS
MVC
OLT
OMG
OO
message format services
model-view-controller
object level trace
EJB
EJS
FTP
GUI
Enterprise JavaBeans
Enterprise Java Server
File Transfer Protocol
Object Management Group
object-oriented
graphical user interface
Hypertext Markup Language
HTML
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OTS
object transaction service
WS
Web service
RAD
rapid application development
WSBCC
WebSphere Business
Components Composer
RDBMS
relational database
management system
WSDL
Web Service Description
Language
RMI
Remote Method Invocation
Simple API for XML
WSTK
WTE
WWW
XMI
Web Service Development Kit
WebSphere Test Environment
World Wide Web
SAX
SCCI
source control control
interface
SCM
software configuration
management
XML metadata interchange
eXtensible Markup Language
XML Schema definition
XML
SCMS
source code management
systems
XSD
SDK
Software Development Kit
Service Mapping Registry
SMR
SOAP
Simple Object Access
Protocol (a.k.a. Service
Oriented Architecture
Protocol)
SPB
SQL
Stored Procedure Builder
structured query language
Service Registry Proxy
secure socket layer
SRP
SSL
TCP/IP
Transmission Control
Protocol/Internet Protocol
UCM
UDB
UDDI
Unified Change Management
Universal Database
Universal Description,
Discovery, and Integration
UML
UOW
URL
Unified Modeling Language
unit-of-work
uniform resource locator
visual composition editor
VCE
VXML
voice extensible markup
language
WAR
WAS
Web application archive
WebSphere Application
Server
WML
Wireless Markup Language
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Related publications
The publications listed in this section are considered particularly suitable for a
more detailed discussion of the topics covered in this redbook.
IBM Redbooks
For information on ordering these publications, see “How to get IBM Redbooks”
on page 316.
ꢀ
ꢀ
ꢀ
ꢀ
Web Services Wizardry with WebSphere Studio Application Developer,
SG24-6292-00
Self-Study Guide: WebSphere Studio Application Developer and Web
Services , SG24-6407-00
WebSphere Studio Application Developer Programming Guide,
SG24-6585-00
DB2 UDB e-business Guide, SG24-6539-00
Other resources
These publications are also relevant as further information sources:
Java and XSLT, O’Reilly, 0-596-00143-6
ꢀ
Referenced Web sites
These Web sites are also relevant as further information sources:
ꢀ Developing XML Web services with WebSphere Studio Application
Developer:
ꢀ IBM WebSphere Developer Technical Journal:
ꢀ XML Bible, Second Edition:
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315
How to get IBM Redbooks
You can order hardcopy Redbooks, as well as view, download, or search for
Redbooks at the following Web site:
You can also download additional materials (code samples or diskette/CD-ROM
images) from that site.
IBM Redbooks collections
Redbooks are also available on CD-ROMs. Click the CD-ROMs button on the
Redbooks Web site for information about all the CD-ROMs offered, as well as
updates and formats.
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Index
DTD Repository 130
DTD to XSD 146
DXX 200
A
Access Beans 245
AlphaWorks 13
Animated GIF Designer 73
Apache Tomcat 78
Application Server 71
Apply XSL 96
DxxInvoker 200
Attribute 182
E
ebXML 6
Edit Join Conditions 197
EJB 71, 238
Element 42, 110
EncryptedData 36
Enterprise 72
Enterprise Architecture Integration 6
Enterprise Developer 72
Enterprise Generation Language 72
Entity EJB 239
C
ClearCase LT 76
CMP 239
Cocoon 49
Concurrent Versions System 76
Conditional (XQuery) 43
Container Managed Persistence 175
Copy file transfer mechanism 292
CSS 21
D
F
DAD 131, 171, 196
DAD Extension 199
DAD extension 98
Filtering 44
FLWR 43
Foreign key as links 109
FTP file transfer mechanism 292
DADX 164, 171
DADX Group 200
datasource 278
Developer Resource Portal 72
Diskspace 306
DOM 19, 48, 57, 67, 165, 175, 218, 228, 250
DOM Level2 62
DRP 72
G
Generate DADX 202
Generate XML 184
Generate XML Schema 122
Generating XSL from XHTML 188
Genrrate XSL 186
Global Element 181
GML 9
DSA 38
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group.properties 201
Primary key as attributes 106
produceDOMDocument 228, 265
H
HTML and mapping approach 184
HTML from XSD 151
HTTPRequest 265
Q
Quantifiers 44
Query Template 117
Querying Relational Data 45
QueryProperty 270
I
IBM DB2 XML Extender 75
Availability Version 5 300
Install 302
R
RDB to XML Mapping 196
Recurse though foreign key 109
Recurse through foreign keys 104
Installing EAR 285
Integration Edtion 72
Introspect 223
J
Java Proxy 212
S
SAML 40
SAX2 58
JavaScript 73
Schema 263
Schema Files 237
JAXP 48, 174, 190, 212, 230, 267
JDBC 56
Security Options 308
Servlet 71, 175
JDBC data source 247
JNDI 176
setup.exe 307
SGML 9
JSP 71
SHA-1 38
Signature 40
Simple Project 179
M
N
SQL mapping 137
SQL to/from XML 258
SqlProperties 264
SQLResult 112, 262, 266
SQLToXML 270
Namespace 88
namespace prefix 24
Namespaces 23
Navigator 103
Net Search Extender 126
Standard Generalized Markup Language 9
Start application server 309
Stylesheet Compilation 68
P
Plug-in Development Environment 78
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SVG 50
Xalan 57
Xerces 19, 57
XHTML 188
XKMS 40
XLink 25
XML 1.0 specifications 10
XML Base 28
XML Collection Operations 203
XML Digital 34
T
Testing the XSL 189
Text Extender 126
Transformer 192
Transforms 38
TrAX 48
Tree-based parsing 18
U
XML Document 265
XML Editor 81–82
XML from DTD 147
UDF 200
UDT 200
Uniform Resource Identifier 24
Universal Description Discovery and Integration
13, 76
URI 24
XML Parser for Java 19
XML Perspective 80
XML Pointer 29
XML processor 18
XML Query Language 40
XML security 40
V
Validating DTD 85
Validating schema 88
VBScript 73
XML to SQL wizard 119
XMLCLOBFromFile 127
XMLToSQL library 259
Voice XML 7
W
WAS_V4_XALAN 190
Web Art Designer 73
Web Project 180
XPointer
path 30
Range 31
String 32
XSD Editor 85
WebSphere administrative server 309
WebSphere Application Server Attention 308
WebSphere Test Environment 253
Workspace 302
XSD to DTD 146
xsl variable 269
XSL/XML /from HTML 156
XSL-FO 21, 50
WSAA 72
XSLServlet 217
XSLT 20, 47, 56, 75, 167, 178, 216
XSLT Processor 259
X
XACML 40
Index
319
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XSLTC 48, 65
320
The XML Files: Development of XML/XSL Applications Using WebSphere Studio
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®
The XML Files:
Development of XML/XSL Applications
Using WebSphere Studio Version 5
Introduces
WebSphere Studio
Application
Developer Version 5
XML tooling
Extensible Markup Language (XML) has very quickly gathered
a large number of industry supporters. Therefore, a significant
number of XML-based conferences, books, Web sites, and
training classes have sprung up. The book was written for
those interested in designing and developing Web
applications using XML and related technologies (XSL, XSLT).
Project managers, architects, and developers will find this
book particularly useful.
INTERNATIONAL
TECHNICAL
SUPPORT
ORGANIZATION
A comprehensive
guide to XML support
of WebSphere Family
BUILDING TECHNICAL
INFORMATION BASED ON
PRACTICAL EXPERIENCE
We start with an overview of XML technology. Then we
explain how to apply XML technology with IBM WebSphere.
Finally, we show a sample application written using the
technologies described. Source code and installation steps
are also available.
Start-to-finish
application case
studies
IBM Redbooks are developed by
the IBM International Technical
Support Organization. Experts
from IBM, Customers and
Partners from around the world
create timely technical
This IBM Redbook applies to IBM WebSphere Studio
Application Developer V5.0.
information based on realistic
scenarios. Specific
recommendations are provided
to help you implement IT
solutions more effectively in
your environment.
For more information:
ibm.com/redbooks
SG24-6586-00
ISBN 0738426873
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