Java and XML, Second Edition

Even More Handlers

Now I want to show you two more handler classes that SAX offers. Both of these interfaces are no longer part of the core SAX distribution, and are located in the org.xml.sax.ext package to indicate they are extensions to SAX. However, most parsers (such as Apache Xerces) include these two classes for use. Check your vendor documentation, and if you don’t have these classes, you can download them from the SAX web site. I warn you that not all SAX drivers support these extensions, so if your vendor doesn’t include them, you may want to find out why, and see if an upcoming version of the vendor’s software will support the SAX extensions.

LexicalHandler

The first of these two handlers is the most useful: org.xml.sax.ext.LexicalHandler . This handler provides methods that can receive notification of several lexical events such as comments, entity declarations, DTD declarations, and CDATA sections. In ContentHandler, these lexical events are essentially ignored, and you just get the data and declarations without notification of when or how they were provided.

This is not really a general-use handler, as most applications don’t need to know if text was in a CDATA section or not. However, if you are working with an XML editor, serializer, or other component that must know the exact format of the input document, not just its contents, the LexicalHandler can really help you out. To see this guy in action, you first need to add an import statement for org.xml.sax.ext.LexicalHandler ...