This book is sharply focused. It concentrates on only those Web services standards that are sanctioned by the Web Services Interoperability Organization's Basic Profile 1.0, because these are the only standards that have been proven in production and are explicitly required by the J2EE Web Services platform. This book also covers only those J2EE APIs and components that are specific to Web services. The truth is, the primary Web service standards (XML, SOAP, WSDL, and UDDI), as well as the J2EE Web Services APIs (JAX-RPC, SAAJ, JAXR, and JAXP), are pretty complicated, and you are going to need to spend time studying this book in order to master them. That said, I think you will find this book to be a pretty easy read and an excellent desk-side reference.

Are Web Services Important?

Revolutionary technologies tend to take the media by storm and then eventually become ubiquitous. The World Wide Web, Java technology, and XML seem to be everywhere, don't they? Each of these technologies saw rapid adoption and today are considered essential ingredients of enterprise-level computing.

First introduced in 2000, Web services is also a revolutionary technology. It was introduced with a great deal of media hyperbole, but has since settled down to business and is just beginning to enjoy rapid adoption by the developer community. If you did not get involved in Web services before 2003, don't worry; you didn't miss much. The first two years should be considered experimental, the beta period of Web services. It was a time when the Web services community defined a cornucopia of specifications and discovered numerous real-world problems when attempting to make those specifications work in production. The year 2003, however, marks the beginning of hyperactive growth in Web services. If you are just jumping on board the Web services bandwagon, your timing couldn't be better. Consider yourself a pioneer of a revolutionary technology, and prepare to immerse yourself in one of the most important innovations in the history of distributed computing.

What Do I Need to Know to Read This Book?

This book is written for Java developers who want to learn about Web services and related APIs defined by J2EE 1.4. It is more of a reference than a tutorial, but many of the chapters have a tutorial-like style. This book is designed to teach J2EE Web Services and is more than a reference.

You must have experience in the Java programming language to read this book. If you don't, you'll find all the material after Chapter 9 difficult to understand. In addition, you should have some basic understanding of the J2EE platform. This book covers only the Web services functionality of J2EE, not other J2EE APIs or technologies.

To read this book, you do not need to know anything about XML, SOAP, WSDL, UDDI, or any of the J2EE Web Services APIs (JAX-RPC, SAAJ, JAXR, or JAXP). I've covered these topics in enough detail that I'm confident even a complete novice will be able to understand them.

What Does This Book Cover?

This book focuses only on the Web services standards and the J2EE 1.4 Web Services APIs and components—all other topics are deferred to other specialized books or to more general books. Specifically this book covers the following Web service standards:

• XML 1.0
• SOAP 1.1
• SOAP Messages with Attachments
• WSDL 1.1
• UDDI 2.0
• WS-I Basic Profile 1.0

The Web services standards take up the first third of the book, Chapters 1-8, while the rest of the book focuses on the J2EE Web Services APIs:

• JAX-RPC 1.1
• SAAJ 1.2
• JAXR 1.0
• JAXP 1.2

This book covers the use of the Web Services APIs as specified in J2EE 1.4 because version 1.4 is the first Java platform that fully embraces the Web service paradigm.

How Is This Book Organized?

The book is designed as a reference and a tutorial about J2EE Web Services. The chapters tend to build on one another. Once you read Part I on XML, you are prepared to read Part II on SOAP and WSDL. Similarly, before you read Part IV on JAX-RPC (Java API for XML-based RPC) you should understand XML, SOAP, and WSDL. Once you have read this book and understand J2EE Web services, it should continue to be very helpful as a reference. You can use it in your everyday work to look up information about Web service standards and the J2EE 1.4 Web Services APIs.

The book is divided into seven parts, each of which is made up of two or more chapters about a specific Web service standard or J2EE API, plus one introductory chapter. Each part begins with an introduction page that tells you how to read the chapters, and specifically which parts you really must read and which parts are optional reference material.

Every chapter is organized into four to five levels of headings labeled with a hierarchical dot notation. This labeling scheme is used in many specifications today, and is particularly useful for a reference book because it makes it much easier to discuss certain portions of the book with your colleagues. The book also includes appendices that cover important topics like XML regular expressions, Base64 encoding, DTDs, SOAP Messages with Attachments, and RPC/Encoded messaging.

The following outline of the book includes a short description of each chapter.

• Chapter 1 summarizes the topics covered by this book, presents a brief architectural overview of J2EE 1.4, and provides abstracts about XML, SOAP, WSDL, UDDI, WS-I, JAX-RPC, SAAJ, JAXR, and JAXP.

Chapters 2 and 3 cover in detail XML 1.0 and the XML Schema standard defined by the World Wide Web Consortium (W3C). This part assumes you have no prior knowledge of XML and explains the topic from the ground up.

• Chapter 2 covers XML and XML namespaces.
• Chapter 3 provides both basic and advanced coverage of the W3C's XML Schema standard.

Chapters 4 and 5 gently introduce SOAP 1.1 and WSDL 1.1. This part assumes you are already familiar with XML, XML namespaces, and XML schema as described in Part I.

• Chapter 4 explains the structure of SOAP messages, terminology, and processing rules.
• Chapter 5 covers WSDL 1.1.

Chapters 6 through 8 provide a reference to the UDDI 2.0 data types, and to query and publishing methods. This part of the book assumes you are already familiar with XML, XML schema, SOAP, and WSDL as covered in Parts I and II.

• Chapter 6 provides a gentle introduction to the UDDI data types.
• Chapters 7 and 8 are pure reference material; they provide schema information about the UDDI Inquiry and Publishing APIs.

Chapters 9 through 15 provide very detailed coverage of the entire Java API for XML-based RPC (JAX-RPC), version 1.1. This part assumes you already know XML, XML schema, SOAP, and WSDL.

• Chapter 9 introduces various features of JAX-RPC.
• Chapter 10 covers JAX-RPC service endpoints (JSEs) and their relationship to the servlet container system.
• Chapter 11 covers EJB endpoints, EJB stateless session beans that act as Web services.

• Chapter 13 covers the use of SAAJ 1.2.
• Chapter 14 describes the use and configuration of message handlers, which are used to pre- and post-process SOAP messages.
• Chapter 15 covers Java-to-WSDL and Java-to-XML mapping, which describes how XML and WSDL types are translated into Java code.

Chapters 16 through 19 cover in detail the Java API for XML Registries (JAXR), version 1.0. Specifically they explain how to use the JAXR API to publish and query information in a UDDI registry.

• Chapter 16 gives you an overview of JAXR and helps you prepare for subsequent chapters.
• Chapter 17 and 18 present a detailed study of the JAXR domain objects that are mapped to UDDI data types.
• Chapter 19 covers the JAXR Inquiry and Publishing APIs, which can be used to query, add, and update information in a UDDI registry.

Chapters 20 and 21 serve as a primer on the Java API for XML Processing, version 1.2. Specifically they cover the use of SAX2 and DOM 2.

• Chapter 20 covers SAX2, the event-driven XML parser API.
• Chapter 21 covers the DOM 2 XML parser API.

Chapters 22 through 24 provide a detailed study of the XML deployment descriptors used in J2EE Web Services, as well as an overview of JAR packaging and deployment.

• Chapter 22 covers general J2EE deployment descriptors used for deploying JSEs and EJB endpoints.
• Chapter 23 covers the Web service-specific deployment descriptors as defined by the Web Services for J2EE (WS-J2EE) specification.
• Chapter 24 covers the JAX-RPC mapping file, which determines how WSDL and XML types are mapped to Java interfaces and Java beans.

• What Doesn't This Book Cover?

As I said at the start of this preface, this book focuses only on standard Web service technologies and the core J2EE 1.4 Web Services APIs. There is simply too much material in this book to allow for coverage of other topics.

Non-Web Service Aspects of the J2EE Platform

Although this book provides detailed coverage of the J2EE 1.4 Web Services APIs, as well as an overview of servlets and EJBs, J2EE is too large a topic to cover comprehensively. It's expected that you have some general knowledge about J2EE or that you will seek to learn more about the J2EE platform and APIs unrelated to Web services from other resources.

The author of this book has written two other J2EE books: Enterprise JavaBeans (Fourth Edition, O'Reilly 2004) and Java Message Service (with David A. Chappell, O'Reilly, 2000).

Vendor-Specific Configuration and Administration

There is a wide variety of J2EE platforms for you to choose from: BEA's WebLogic, IBM's WebSphere, Sun Microsystems' Sun ONE, Oracle9i Application Server, IONA's Application Server Platform, Apple WebObjects, Borland Enterprise Server, Pramati's Pramati Server, the Apache J2EE, jBoss and ObjectWeb open source projects, and many others. While each of these platforms adheres to the J2EE specification, they all specify very different procedures and interfaces for installing, configuring, and deploying applications. Because the administration of each J2EE platform is different, this book doesn't attempt to cover installation, configuration, or deployment except in terms of standard J2EE requirements. To learn about vendor-specific administration and configuration requirements, please consult the vendor's documentation.

Other Web Service "Standards"

There are a number of new Web service standards that have been proposed by various organizations (W3C, OASIS, ebXML, and IBM/Microsoft ) including things like DISCO, WSCI, BTP, WS-Security, DIME, etc. Many of these proposed standards actually conflict or compete with each other. It's unclear which of them will become Web service standards and which of them will die on the vine, so this book covers only the core, WS-I Approved Web service protocols.