Introduction

XML is growing in popularity for use in all kinds of applications. Some have called it the new ASCII, believing that XML will be used as widely as the ASCII character set is today. XML’s simple rules for markup, utilization of Unicode, and endorsement by the World Wide Web Consortium (W3C) have made it a good choice for representing various kinds of data in a human-readable manner. In addition, many new technologies have been built on top of XML—from technologies that convert XML from one vocabulary to another, to those that render formatted XML as PDF or Postscript, all the way to technologies that digitally sign and encrypt XML documents or pieces of XML documents.

To use XML or one of its related technologies, you need to have a toolset, and one such toolset is the topic of this book. The Apache Software Foundation hosts a number of projects related to XML. The aim of this book is to give you an overview of the XML technology the projects implement and then show you how to use the projects in your own applications.

How to Use This Book

This book is intended for Java developers who are already familiar with XML and who want to use one of the Apache XML projects in an application setting. The focus of the book is the unique features of the Apache tools we’ll cover. This isn’t intended to be a tutorial book for any of the XML technologies standardized by the W3C. In particular, you shouldn’t use this book as a tutorial on XML, XML Namespaces, SAX, DOM, XSLT, XSL, SVG, SOAP, WSDL, XML Signature, or XML Encryption. Although each chapter contains some material to make sure that you can understand the functionality provided by the Apache projects, each one of these technologies could be the subject of an entire book (and many of them are). Our goal is to help you see how to use the Apache libraries to perform the kinds of tasks needed to build real-world applications.

This book also doesn’t cover every Apache XML-related project—a book must have a finite scope, just like a software project. We’ll examine the most useful tools provided by Apache, as well as real-world techniques for using them.

Unless noted, all the examples have been written for and tested under the Java SDK version 1.4.2. Many of the examples will run fine on earlier versions of the JDK, but a few will not, and these are noted for you.

The tools presented are mostly independent of one another, with the exception of Xerces. XML parsing is a fundamental aspect of all the Apache XML tools, so knowledge of Xerces can be helpful in many circumstances. It would be a good idea for you to at least browse the contents Chapter 1, “Xerces,” to make sure you’re familiar with all the concepts. After that, you can jump to the chapter that discusses the particular tool you’re interested in.

Note

All the code and sample applications in this book can be downloaded from www.wrox.com.