The ability to save the JavaBean component state for long-term persistence within an XML document has been a topic of much discussion with Java developers in the past few years. This feature has finally been adopted in the 1.4 version of J2SE. In this installment of Magic with Merlin, John Zukowski shows you how to use the new XMLEncoder and XMLDecoder classes, bypassing serialization and allowing you to generate fully initialized bean instances. One new feature of Merlin has been thrown around in various incarnations at Sun's Swing Connection for some time now; in fact, it was first discussed at the 1999 JavaOne show. That feature is the ability to save the JavaBean component state for long-term persistence within an XML document. Serialization works fine for short-term marshaling needs, with CORBA and RMI, or for saving state information within an executing servlet. However, serialization can run into problems across versions of class libraries or Java run-time environments, among many other issues. The new XMLEncoder / XMLDecoder classes permit the dumping of the JavaBean component state to a text file for easy modification outside of a Java program or more likely for the generation of such files. Let's take a look at how to use the classes and examine the file generated.

This is the first in a series of tips that will serve as a comprehensive guide to using XML from the Java programming language. I begin with coverage of the SAX API. This tip reviews getting an instance of a SAX parser and setting various features and properties on that parser. Working with XML from Java is a pretty rich topic; multiple APIs are available, and many of these make working with XML as easy as reading lines from a text document. Tree-based APIs like DOM present an in-memory XML structure that is optimal for GUIs and editors, and stream-based APIs like SAX are great for high-performance applications that only need to get at a document's data. In this series of tips, I walk you through the use of XML from Java, starting with the basics. Along the way, you'll learn lots of tricks that many of the pros don't even know about, so stick around even if you already have some XML experience.

XML developers used to rely on XML parsers to read XML files. They also used to rely on XML processors to transform XML to *ML (HTML, XML ...). However, most of them forget these tools to generate XML from scratch.