This helper class implements the four commonly-used SAX handler interfaces from the org.xml.sax package and defines stub implementations for all of their methods. It is usually easier to subclass DefaultHandler and override the desired methods than it is to implement all of the interfaces (and all of their methods) from scratch. DefaultHandler implements ContentHandler, ErrorHandler, EntityResolver and DTDHandler, so you can pass an instance of this class, (or of a subclass you define) to the setContentHandler( ), setErrorHandler( ), setEntityResolver( ), and setDTDHandler( ) methods of an XMLReader. You can also pass an instance of a DefaultHandler subclass directly to one of the parse( ) methods of a javax.xml.parsers.SAXParser. The SAXParser will take care of calling the four relevant methods of its internal XMLReader.

All but two of the methods of DefaultHandler have empty bodies and do nothing. The exceptions are resolveEntity( ) which simply returns null to tell the parser to resolve the entity itself, and fatalError( ) which throws the SAXParseException object that is passed to it.

Figure 22-15. org.xml.sax.helpers.DefaultHandler

public class DefaultHandler implements org.xml.sax.ContentHandler, 
        org.xml.sax.DTDHandler, org.xml.sax.EntityResolver, 
        org.xml.sax.ErrorHandler {
// Public Constructors
     public DefaultHandler( );  
// Methods Implementing ContentHandler
     public void characters(char[ ] ch, int start, int length) 
        throws org.xml.sax.SAXException;     empty
     public void endDocument( ) throws org.xml.sax.SAXException;          empty
     public void endElement(String uri, String localName, String qName) 
        throws org.xml.sax.SAXException;     empty
     public void endPrefixMapping(String prefix) throws org.xml.sax.SAXException;     empty
     public void ignorableWhitespace(char[ ] ch, int start, int length) 
        throws org.xml.sax.SAXException;     empty
     public void processingInstruction(String target, String data) 
        throws org.xml.sax.SAXException;     empty
     public void setDocumentLocator(org.xml.sax.Locator locator);       empty
     public void skippedEntity(String name) throws org.xml.sax.SAXException;     empty
     public void startDocument( ) throws org.xml.sax.SAXException;        empty
     public void startElement(String uri, String localName, String qName, 
        org.xml.sax.Attributes attributes) 
        throws org.xml.sax.SAXException;     empty
     public void startPrefixMapping(String prefix, String uri) 
        throws org.xml.sax.SAXException;     empty
// Methods Implementing DTDHandler
     public void notationDecl(String name, String publicId, String systemId) 
        throws org.xml.sax.SAXException;     empty
     public void unparsedEntityDecl(String name, String publicId, String systemId, 
        String notationName) 
        throws org.xml.sax.SAXException;     empty
// Methods Implementing EntityResolver
     public org.xml.sax.InputSource resolveEntity(String publicId, String systemId) 
throws java.io.IOException, org.xml.sax.SAXException;     constant
// Methods Implementing ErrorHandler
     public void error(org.xml.sax.SAXParseException e) 
        throws org.xml.sax.SAXException;     empty
     public void fatalError(org.xml.sax.SAXParseException e) 
        throws org.xml.sax.SAXException;  
     public void warning(org.xml.sax.SAXParseException e) 
        throws org.xml.sax.SAXException;     empty
}

Subclasses

org.xml.sax.ext.DefaultHandler2

Passed To

javax.xml.parsers.SAXParser.parse( )