Java and XML

Chapter 5. Validating XML

Your knowledge base and accompanying bag of XML tricks should be starting to feel a little more solid by now. You can create XML, use the Java SAX classes to parse through that XML, and now constrain that XML. This leads us to the next logical step: validating XML with Java. Without the ability to validate XML, business-to-business and inter-application communication becomes significantly more difficult; while constraints enable portability of our data, validity ensures its consistency. In other words, being able to constrain a document doesn’t help much if we can’t ensure that those constraints are enforced within our XML applications.

In this chapter, we will look at using additional SAX classes and interfaces to enforce validity constraints in our XML documents. We will examine how to set features and properties of a SAX-compliant parser, allowing easy configuration of validation, namespace handling, and other parser functionality. In addition, the errors and warnings that can occur with validating parsers will be detailed, filling in the blanks from earlier discussions on the SAX error handlers.

Configuring the Parser

With the wealth of XML-related specifications and technologies emerging from the World Wide Web Consortium (W3C), adding support for any new feature or property of an XML parser has become difficult. Many parser implementations have added proprietary extensions or methods at the cost of the portability of the code. While these software packages ...