org.atzberger.application.selm_builder
Class XMLContentHandler

java.lang.Object
  org.xml.sax.helpers.DefaultHandler
      org.xml.sax.ext.DefaultHandler2
          org.atzberger.application.selm_builder.XMLContentHandler

All Implemented Interfaces:

org.xml.sax.ContentHandler, org.xml.sax.DTDHandler, org.xml.sax.EntityResolver, org.xml.sax.ErrorHandler, org.xml.sax.ext.DeclHandler, org.xml.sax.ext.EntityResolver2, org.xml.sax.ext.LexicalHandler

public abstract class XMLContentHandler
extends org.xml.sax.ext.DefaultHandler2

XMLContentHandler provides a structured approach to building a data structure from XML content using SAX parser. Generally most of the data structures can be built in a top down approach where a parent gets created first and then children add themselves to the parent. This utility class facilitates building data structures in such a top down approach. The default content handler provided by SAX API is not conducive to building a data structure. So a programmer ends up in storing parent context of an element as a transient attribute of the handler, but this does not scale up. For every level of depth, a separate attribute needs to be created. This utility class provides parent element as the context while creating child element and hence allows building a data structure top down. This utility also provides the element context while reading CDATA and TEXT sections of an element. In order to make use of this feature, certain properties have to be set up as follows...

 SAXParser parser = ...
 XMLContentHandler handler = ... //an instance of a subclass of XMLContentHandler
 parser.setProperty("http://xml.org/sax/properties/lexical-handler", handler);
 

In order to make use of XMLContentHandler, user has to subclass this and provide implementation for the following methods ...

 
 createElement, processText and processCDATA.
 

Author:

venkatm (http://www.javalobby.org/java/forums/t104100.html) This code is in the public domain, see above link for details.

Constructor Summary

XMLContentHandler()

Method Summary

void	characters(char[] ch, int start, int length)
protected abstract XMLElement	createElement(XMLElement parent, java.lang.String name, org.xml.sax.Attributes attributes) Subclasses provide an implementation for this.
void	endCDATA()
void	endElement(java.lang.String uri, java.lang.String localName, java.lang.String name)
protected XMLElement	newXMLElement(XMLElement parent, java.lang.Object value)
protected XMLElement	nullXMLElement(XMLElement parent) Give a call to this to create null valued XML elements.
protected abstract void	processCDATA(XMLElement parentElement, XMLElement element, java.lang.String str)
protected abstract void	processText(XMLElement parentElement, XMLElement element, java.lang.String name, java.lang.String str)
void	startCDATA()
void	startElement(java.lang.String uri, java.lang.String localName, java.lang.String name, org.xml.sax.Attributes attributes)

Methods inherited from class org.xml.sax.ext.DefaultHandler2

attributeDecl, comment, elementDecl, endDTD, endEntity, externalEntityDecl, getExternalSubset, internalEntityDecl, resolveEntity, resolveEntity, startDTD, startEntity

Methods inherited from class org.xml.sax.helpers.DefaultHandler

endDocument, endPrefixMapping, error, fatalError, ignorableWhitespace, notationDecl, processingInstruction, setDocumentLocator, skippedEntity, startDocument, startPrefixMapping, unparsedEntityDecl, warning

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

XMLContentHandler

public XMLContentHandler()

Method Detail

startElement

public void startElement(java.lang.String uri,
                         java.lang.String localName,
                         java.lang.String name,
                         org.xml.sax.Attributes attributes)
                  throws org.xml.sax.SAXException

Specified by:

startElement in interface org.xml.sax.ContentHandler

Overrides:

startElement in class org.xml.sax.helpers.DefaultHandler

Throws:

org.xml.sax.SAXException

createElement

protected abstract XMLElement createElement(XMLElement parent,
                                            java.lang.String name,
                                            org.xml.sax.Attributes attributes)
                                     throws java.lang.Exception

Subclasses provide an implementation for this.

Parameters:

parent - Represents the parent element created before. It is null for the root element

name - Represents the name of the XML element.

attributes - Represents the attributes of the XML element

Returns:

element.

Throws:

java.lang.Exception

newXMLElement

protected XMLElement newXMLElement(XMLElement parent,
                                   java.lang.Object value)

nullXMLElement

protected XMLElement nullXMLElement(XMLElement parent)

Give a call to this to create null valued XML elements. This would be helpful when an xml element represents just a value rather an object of its own. Very often primitive valued properties of an object are represented by an individual xml element.

Parameters:

parent -

Returns:

element

endElement

public void endElement(java.lang.String uri,
                       java.lang.String localName,
                       java.lang.String name)
                throws org.xml.sax.SAXException

Specified by:

endElement in interface org.xml.sax.ContentHandler

Overrides:

endElement in class org.xml.sax.helpers.DefaultHandler

Throws:

org.xml.sax.SAXException

processText

protected abstract void processText(XMLElement parentElement,
                                    XMLElement element,
                                    java.lang.String name,
                                    java.lang.String str)
                             throws java.lang.Exception

Parameters:

parentElement - It is null when element represents root.

element -

name -

str -

Throws:

java.lang.Exception

endCDATA

public void endCDATA()
              throws org.xml.sax.SAXException

Specified by:

endCDATA in interface org.xml.sax.ext.LexicalHandler

Overrides:

endCDATA in class org.xml.sax.ext.DefaultHandler2

Throws:

org.xml.sax.SAXException

processCDATA

protected abstract void processCDATA(XMLElement parentElement,
                                     XMLElement element,
                                     java.lang.String str)
                              throws java.lang.Exception

Throws:

java.lang.Exception

startCDATA

public void startCDATA()
                throws org.xml.sax.SAXException

Specified by:

startCDATA in interface org.xml.sax.ext.LexicalHandler

Overrides:

startCDATA in class org.xml.sax.ext.DefaultHandler2

Throws:

org.xml.sax.SAXException

characters

public void characters(char[] ch,
                       int start,
                       int length)
                throws org.xml.sax.SAXException

Specified by:

characters in interface org.xml.sax.ContentHandler

Overrides:

characters in class org.xml.sax.helpers.DefaultHandler

Throws:

org.xml.sax.SAXException