The XMLService Class

//: XMLService.java

package com.owensum.everest.xml;

import java.util.*;
import java.io.*;

import org.w3c.dom.*;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.apache.xml.serialize.XMLSerializer;
import org.apache.xml.serialize.OutputFormat;
import org.apache.xerces.parsers.DOMParser;

/** Use this class to process xml requests.  This class expects the xml request
  * adheres to IFX
  *
  * @author Greg Thompson
  * @version 1.0
  */
public class XMLService {

    // the impl for xml document.
    public final static String CLASS_NAME_DOCUMENT = "org.apache.xerces.dom.DocumentImpl";

    // private constructor
    private XMLService() {

	// create new handlers hash map
	_handlers = new HashMap();

	// add currently known handlers
	addElementHandler( CarrierInfoInqRqHandler.TAG_CARRIER_INFO_INQ_RQ, new CarrierInfoInqRqHandler() );
	addElementHandler( EPLIFactorsInqRqHandler.TAG_EPLI_FACTORS_INQ_RQ, new EPLIFactorsInqRqHandler() );
	.
	.
	.
    }

    /** This is the process request method.  It is used to process an xml docuemnt.
      * It expects that the document is in IFX format.  It tries to login using the signonrq.
      *
      * @param doc the request document
      * @return the response document
      * @exception Exception
      */
    public Document processRequest( Document request ) 
	throws Exception
    {
	// login and get the user
	User user = login( request );

	// get root element
	Element root = request.getDocumentElement();

	// create the response doc
	Document response = (Document) Class.forName( CLASS_NAME_DOCUMENT ).newInstance();

	// handle the root element
	Element newRoot = handleElement( user, response, root );
	
	// append the new root
	response.appendChild( newRoot );

	// return the response
	return response;
    }

    /** This method is to recursively handle the elements of a request document.  For each child element
      * of the given element, if there is a registered element handler, then it passes that element to 
      * the handler.  If not, call handle element (recursive, drill down).  If the element has no children, 
      * return null.
      *
      * The element handler should take a request transaction, and return the response.
      * 
      * @param doc the request document
      * @return the response document
      * @exception Exception
      */
    private Element handleElement( User user, Document doc, Element element ) 
	throws Exception
    {
	// get child nodes of root element
	NodeList nodes = element.getChildNodes();

	// if no child nodes
	if ( nodes.getLength() == 0 )
	    return null;

	// create new element based on the same name as the given element
	Element newElement = doc.createElement( element.getNodeName() );

	// iterate over child nodes
	for ( int i = 0; i < nodes.getLength(); i++ ) {
	    Node node = nodes.item( i );
	    
	    // if the node is an element, then handle the element
	    if ( node.getNodeType() == node.ELEMENT_NODE ) {

		//System.out.print( "Node: " + node.getNodeName() + " ");
		Element e = (Element) node;

		// handle the element
		ElementHandler h = (ElementHandler) _handlers.get( node.getNodeName() );

		Element ne = null;

		// if there is a element handler, then call it
		if ( h != null ) {
		    //System.out.println( "(ElementHandler: Yes)" );
		    ne = h.handleElement( user, doc, e );
		}
		// if not, drill down
		else {
		    //System.out.println( "(ElementHandler: No)" );
		    ne = handleElement( user, doc, e );
		}

		// if the response is not null, add it
		if ( ne != null )
		    newElement.appendChild( ne );
	    }
	}

	// return the new element ( response )
	return newElement;
    }

    /** Use this method to create an xml document (dom) from a stream.
      *
      * @param inputStream the input stream of the xml document
      * @return the document create from the stream
      * @exception IOException
      * @exception SAXException
      */
    public Document createDocument( InputStream is ) 
	throws IOException, SAXException
    {
	DOMParser parser = new DOMParser();
	parser.parse( new InputSource( is ) );
	return parser.getDocument();
    }
	.
	.
	.
}