com.nt.udc.util.xml

Class ContextParser

java.lang.Object

org.xml.sax.helpers.DefaultHandler

com.nt.udc.util.xml.ContextParser

All Implemented Interfaces:

NamedContextFactory, org.xml.sax.ContentHandler, org.xml.sax.DTDHandler, org.xml.sax.EntityResolver, org.xml.sax.ErrorHandler

Direct Known Subclasses:

NARHandler

public class ContextParser
extends org.xml.sax.helpers.DefaultHandler
implements NamedContextFactory

A basic SAX event handler for parsing XML documents using the com.nt.udc.util.xml framework.

The class is responsible for handling the SAX events from the parser and passing the necessary information to the appropriate ElementContext object. There are to services it provides in doing this:

• A registration service for the ElementContextFactory objects
• A SAX event handler to be used by the parser

The registration service is in the form of the addFactory method. The ContextParser is typically extended to provide a single location where all ElementContext objects can be registered.

 public class ExportHandler extends ContextParser {
    public ExportHandler() {
       addFactory("export", ExportContext.getFactory());
       addFactory("export", ExportContext.getFactory());
       addFactory("systemModel", SystemModelContext.getFactory());
       addFactory("nodeManager", NodeManagerContext.getFactory());
       ...
    }
 }
 

This sub-class can then be used with your favorite SAX2 parser. There are two ways in which this may be used.

• To build object models from XML documents
• To serialize object models as XML documents

When the ContextParser recieves a startElement event from the parser it creates the ElementContext using the ElementContextFactory that has been registered for that element name. If no factory has been registered then the UnknowContext is used. It is left to the parent application to decide how to handle the UnknownContext. Subsequent SAX events are used to populate the necessary information in the ElementContext object. When the endElement event is called, the ContextParser will add the current context to the parent. It is at this point that the ElementContext becomes responsible for associating any created Objects with the rest of the object model.

Constructor Summary

Constructors

Constructor and Description
ContextParser()

Method Summary

Modifier and Type	Method and Description
void	addFactory(java.lang.String elementName, ElementContextFactory context) A registration method to bind an element name to an ElementContextFactory.
void	characters(char[] ch, int start, int length) For internal use only.
ElementContext	createNewContext(java.lang.String name, org.xml.sax.Attributes attrs) For internal use only.
void	endElement(java.lang.String uri, java.lang.String localName, java.lang.String qName) For internal use only.
ElementContext	getContext(java.lang.String name) Used to retrieve the correct ElementContext given an XML element name.
ElementContext	getRoot() Used to access the root ElementContext for this ContextParser.
void	setDocumentLocator(org.xml.sax.Locator locator)
void	startDocument() For internal use only.
void	startElement(java.lang.String uri, java.lang.String localName, java.lang.String qName, org.xml.sax.Attributes attrs) For internal use only.
void	write(ElementContext ctx, XMLWriter writer) For internal use only.

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

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

Methods inherited from class java.lang.Object

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

Constructor Detail

ContextParser

public ContextParser()

Method Detail

addFactory

public void addFactory(java.lang.String elementName,
                       ElementContextFactory context)

A registration method to bind an element name to an ElementContextFactory. When a startElement is recieved from the SAX parser, the element name is used to look-up the appropriate ElementContextFactory which is in turn used to create the correct ElementContext. If no binding exists for that element name, then the UnknowContext will be used.

Parameters:

elementName - The name of the XML element that the ElementContextFactory will be bound to. This string must conform to the rules for XML element names.

context - The ElementContextFactory that creates ElementContext objects for this XML element name.

startDocument

public void startDocument()

For internal use only.

Specified by:

startDocument in interface org.xml.sax.ContentHandler

Overrides:

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

setDocumentLocator

public void setDocumentLocator(org.xml.sax.Locator locator)

Specified by:

setDocumentLocator in interface org.xml.sax.ContentHandler

Overrides:

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

startElement

public void startElement(java.lang.String uri,
                         java.lang.String localName,
                         java.lang.String qName,
                         org.xml.sax.Attributes attrs)
                  throws org.xml.sax.SAXParseException

For internal use only.

Specified by:

startElement in interface org.xml.sax.ContentHandler

Overrides:

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

Throws:

org.xml.sax.SAXParseException

getRoot

public ElementContext getRoot()

Used to access the root ElementContext for this ContextParser. This will correspond to the ElementContext that is used for the document root of the XML document.

Returns:

the root ElementContext for this ContextParser.

getContext

public ElementContext getContext(java.lang.String name)
                          throws org.xml.sax.SAXParseException

Used to retrieve the correct ElementContext given an XML element name. Using the given name, this method will retrieve a new ElementContext using the ElementContextFactory bound against that name. If no binding exists then the UnknownContext will be returned.

Specified by:

getContext in interface NamedContextFactory

Parameters:

name - The XML element name which we are retrieving the ElementContext for.

Returns:

The ElementContext bound to the given XML element name.

Throws:

org.xml.sax.SAXParseException - if an execption is caused during the creation of the ElementContext.

createNewContext

public ElementContext createNewContext(java.lang.String name,
                                       org.xml.sax.Attributes attrs)
                                throws org.xml.sax.SAXParseException

For internal use only.

Throws:

org.xml.sax.SAXParseException

endElement

public void endElement(java.lang.String uri,
                       java.lang.String localName,
                       java.lang.String qName)

For internal use only.

Specified by:

endElement in interface org.xml.sax.ContentHandler

Overrides:

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

characters

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

For internal use only.

Specified by:

characters in interface org.xml.sax.ContentHandler

Overrides:

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

write

public void write(ElementContext ctx,
                  XMLWriter writer)
           throws org.xml.sax.SAXException

For internal use only.

Throws:

org.xml.sax.SAXException