Welcome to the third version of Java & XML. Whether you've read either of the prior versions, both, or neither, I think you'll find something interesting in the chapters that follow. Quite a bit has changed since the second version appeared. Specifications that were drafts have been finalized, new APIs have been introduced, and new uses for XML have emerged. Perhaps most significantly, two APIs discussed in the second versionJDOM and JAXBsaw important changes between the prerelease versions available at the time of writing and their eventual final releases. Although I hope that the text of this version never becomes out of date, the rate of change in the Java and XML universe makes this unlikely. Nevertheless, I'm confident the bulk of what's ahead will be useful for years to come, even if some of the details change.

Organization

This tutorial is organized into three sections. The first section, composed of Chapters and , provides a basic introduction to XML and related standards. The secondChapters 3 through 11explains a wide variety of APIs for creating, manipulating, outputting, and pretty much doing anything else to XML documents. The last sectionChapters and describes two important apps for XML. There's also a final chapter and an appendix.



We'll begin with the basics of XML. If you've never used XML before, this chapter will give you all the information you need to proceed with the remainder of the chapters. We briefly touch on the changes between XML 1.0 and 1.1 before introducing XSLT and XPath.



This chapter covers three ways of defining the structure of XML documents: DTDs, W3C XML Schemas, and RELAX NG schemas. It covers how to use these standards to define a structure and how to ensure that a document matches that definition (in other words, to validate a document). You'll also learn how to convert between the various constraint document types.



The Simple API for XML (SAX), our first Java API for handling XML, is introduced in this chapter. The parsing lifecycle is detailed, and the events that can be caught by SAX and used by developers are demonstrated.



We'll push further with SAX in this chapter, covering less-used but still powerful items in the API. You'll learn how to use SAX features and properties to alter the behavior of the SAX parser, use XML filters to chain callback behavior, use XML writers to output XML with SAX, and look at some of the less commonly used SAX handlers like LexicalHandler and DeclHandler.



This chapter moves forward through the XML landscape to the next Java and XML API, the Document Object Model (DOM). You'll learn DOM basics, find out what is in the current specification (DOM Level 3), and how to read and write DOM trees.



Moving on through DOM, you'll learn about the various Level 2 and Level 3 DOM modules like Traversal, Range, Events, Style, HTML, Load and Save, and Validation.



This chapter examines the Java API for XML Processing (JAXP), including the XPath and Validation APIs introduced with JAXP 1.3.



The Streaming API for XML (StAX) is the newest standard Java XML API. You'll learn how to use StAX and how it compares to both SAX and DOM. We also briefly look at a precursor to StAX named XMLPull, which is still in use.



This chapter examines JDOM, a Java-specific object model API. It contains complete coverage of the JDOM 1.0 release.



This chapter examines another Java-specific object model API, dom4j. You'll see how it compares to both JDOM and DOM including the features unique to dom4j like its object-orientated transformation API.



With data binding, your app code does not concern itself with the details of XML documents, only a Java object model. Sun has developed a standard for XML data binding: the Java Architecture for XML Binding (JAXB). In this chapter, you'll learn about JAXB 1.0 and 2.0, as well as the general basics of data binding. We also discuss when it is (and is not) appropriate to use data binding.



This chapter covers using XML documents to syndicate content. Specifically, the RSS standards are examined along with a brief discussion of Atom. You'll see how to create and read RSS feeds using APIs discussed in the earlier chapters as well as an RSS-specific API named ROME. You'll even see how to create your own podcast feed for submission to Apple's iTunes Podcast directory.



In this chapter, we'll look at a variety of techniques for using XML in the presentation, or visual, portion of web apps. You'll see how XML is a key component of the dynamic web app techniques quickly moving from the bleeding edge to the mainstream.



This final chapter provides some brief overviews of technologies not covered in depth in this tutorial. Readers hungry for more may want to pursue these topics further.



This appendix details the features and properties available to SAX 2.0 parser implementations.

Conventions Used in this tutorial

The following typographical conventions are used in this tutorial:


Constant width

Indicates command-line elements, computer output, and code examples.


Constant width italic

Indicates placeholders (for which you substitute an actual name) in examples and in registry keys. 


Constant width bold

Indicates user input and is used to highlight key portions of code.


Italic

Introduces new terms and example URLs, commands, file extensions, filenames, and directory or folder names

Java Tip Indicates a tip, suggestion, or general note.
Java Warning Indicates a warning or caution.

Using Code Examples

This book is here to help you get your job done. In general, you may use the code in this tutorial in your programs and documentation. You do not need to contact us for permission unless you're reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this tutorial does not require permission. Selling or distributing a DVD of examples from Oracle tutorials does require permission. Answering a question by citing this tutorial and quoting example code does not require permission. Incorporating a significant amount of example code from this tutorial into your product's documentation does require permission. We appreciate, but do not require, attribution. An attribution usually includes the title, author, uploader, and . For example: "Java & XML, by Brett McLaughlin and Justin Edelson. Copyright 2007 Oracle, 978-0-596-10149-7." If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at permissions@bugmenot.com.

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Acknowledgments

This tutorial would not be possible without the efforts of the Oracle staff, especially our editor, Mike Loukides; his associate, Caitrin McCullough; and the production talents of Marlowe Shaeffer and Linley Dolby. Additional thanks goes out to everyone who reviewed this tutorial, in whole or part; valuable input from Colin Chow, Greg Graf, Noah Jones, Michael Rosencrantz, Victor Toni, and Deepak Vohra improved the tutorial you're reading now. Everyone stands on the shoulders of giants, but this is especially true for writers of a tutorial such as this. For obvious reasons, without the efforts and contributions of developers around the world, the technologies discussed in this tutorial wouldn't exist. There are far too many of you to thank, but you know who you are.

Brett D. McLaughlin

Seeing this tutorial as it prepares to publish as a third version is one of the coolest events of my year, mostly because it's become such a team effort. As I've been pulled into the "dark side" of technical tutorialsthe world of Head FirstI began to wonder if there ever would be a third version of Java & XML. Thanks to the wonderful talents of Justin Edelson, though, you've got an even better tutorial than the first and second versions. Justin came onto this project, added polish and technical detail to the work I'd already done, and cranked out an amazing amount of spectacular material in just a few short months. Justin, I'm proud to have my name next to yours on the cover; you've really added such tremendous value to the tutorial. I always want to thank the Oracle team, and in particular Mike Loukides, for driving this tutorial to completion. This was the tutorial that got me started at Oracle, and it's really gratifying to see so many people pitch in and get this third version out. Thanks, everyone, it's always a joy writing an Oracle tutorial.

Justin Edelson

First and foremost, thanks to Brett and Mike. You took a chance on me, and I can't express how grateful I am. To my wife, Elizabeth, there's no way I could have done this without your help and support. To Owen, it'll be a few years before you read this, but know that you are already an inspiration to me every day. To both my and Beth's parents as well as my sisters and brothers, thanks for everything. To our dogs, Burt and Lola, thanks for occasionally making room on the couch. Thanks to everyone at MTVespecially Lily Chang, Dmitry Grinberg, Steven Hsu, Glenn Goldstein, Greg Clayman, and Nick Rockwellfor all of your support. Thanks to Dan Brustein for being such a great officemate. To the pod, thanks for the last decade; it wouldn't have been the same without you. To Michael Joyce, thanks for the words of wisdom. Finally, I'd like to dedicate this work to my grandfather, Max Edelson, without whom most of the good things in my life (including co-authoring this tutorial) never would have happened.