The org.xml.sax.HandlerBase Handler

All Known Implemented Interfaces: org.xml.sax.DocumentHandler, org.xml.sax.DTDHandler, org.xml.sax.EntityResolver, and org.xml.sax.ErrorHandler

Members

Overview

This helper class provides empty implementation of all SAX 1.0 core handler interfaces, and can be extended to allow addition of handlers by overriding methods with application-defined behavior. This class was defined in SAX 1.0, and is now deprecated. The org.xml.sax.helpers.DefaultHandler class should be used instead of HandlerBase for SAX 2.0 implementations.

            To use JAXP with SAX-compliant parser, your only task is to extend the HandlerBase class and implement the callbacks desired for your application. The alternative in SAX 2.0 is doing the same with DefaultHandler. An instance of your extension class then becomes the core argument for most of the JAXP methods that deals with SAX.

Here’s the typical SAX rundown:

• Create a SAXParser instance using  a specific vendor’s parser implementation.
• Register callback implementations (by using  a class that extends HandlerBase)
• Start parsing and relax as your callback implementations are fired off.
• You only need to implement those callback methods of HandlerBase, that needed for your application.

The SAX component of JAXP provides a simple means to do all of this. Without JAXP, a SAX parser instance either must be instantiated directly from a vendor class ( such as org.apache.xerces.parsers.SAXParser), or it must use a SAX helper class called ParserFactory ( the SAX 1.0 version of SAX 2.0’s XMLReaderFactory).

The JAXP provides a better alternative. It allows you use the vendor class as a parser through a java system property. Please refer your vendor’s documentation for more details regarding the parser factory.

Method Overviews

All most all methods in this class are important. It depends upon your applications needs regarding what are the methods you need to implement in your parser mechanism. Some of the methods are generally used across all SAX parsers. I have listed the methods, those are commonly used across all SAX parsers.

Example of startDocument()

/**

   * This method receives notification, at the start of the XML Document.

   */

  public void startDocument()

  {

    System.out.println("Start of the Document");

  }

Example of startElement()

/**

   * This method receives notification at the start of each element of XMl Document for SAX parser.

   * @param name name of the element

   * @param attributes attributes associated with the element.

   */

  public void startElement(String name, AttributeList attributes)

  {

    System.out.println("Start of the element and Element Name :"+name);

    for (int i = 0; i < attributes.getLength(); i++) {

     String attrname = attributes.getName(i);

     String attrtype = attributes.getType(i);

     String attrvalue = attributes.getValue(i);

     System.out.println("Attribute Name :"+attrname);

     System.out.println("Attribute Type :"+attrtype);

     System.out.println("Attribute Value :"+attrvalue);

   }

  }

Example of characters()

/**

   * Receive notification of character data inside an element.

   * @param ch The characters.

   * @param start The start position in the character array.

   * @param length The number of characters to use from the character array.

   */

  public void characters(char[] ch, int start, int length)

  {

    System.out.println(" Character :"+new String(ch, start,length));

  }

}

Example of How to use HandlerBase

SAXParser parser = SAXParserFactory.newInstance().newSAXParser();

 HandlerBase handlerBase = new HandlerBaseImpl(); //This class extends HandlerBase

parser.parse({InputSource},handlerBase);