Processing XML with Java™: A Guide to SAX, DOM, JDOM, JAXP, and TrAX

The XMLFilterImpl Class

SAX includes an adapter class that you can subclass to build these sorts of two-way filters: org.xml.sax.helpers.XMLFilterImpl. Its general design is similar to what I just detailed, but it implements all of the relevant interfaces in one class:

public class XMLFilterImpl implements XMLFilter, 
 EntityResolver, DTDHandler, ContentHandler, ErrorHandler

When the various setter methods such as setContentHandler() and setErrorHandler() in this class are invoked, the handler is stored in a private field. For example, here is the setContentHandler() method:

public void setContentHandler (ContentHandler handler) 
{
    contentHandler = handler;
}

When the parse() method is called, it swaps out all of the installed handlers for the ...