Metacat

/**

 *        Name: DBSAXHandler.java

 *     Purpose: A Class that handles the SAX XML events as they

 *              are generated from XML documents

 *   Copyright: 2000 Regents of the University of California and the

 *              National Center for Ecological Analysis and Synthesis

 *     Authors: Matt Jones

 *

 *     Version: '$Id: DBSAXHandler.java 51 2000-04-17 23:06:07Z jones $'

 */

package edu.ucsb.nceas.metacat;

import org.xml.sax.*;

import java.sql.*;

import java.util.Stack;

import java.util.EmptyStackException;

// Extensions to the SAX Interfaces for Namespace support.

import oracle.xml.parser.v2.DefaultXMLDocumentHandler;

import oracle.xml.parser.v2.NSName;

import oracle.xml.parser.v2.SAXAttrList;

import oracle.xml.parser.v2.SAXParser;

/** 

 * A database aware Class implementing callback bethods for the SAX parser to

 * call when processing the XML stream and generating events

 */

public class DBSAXHandler extends DefaultXMLDocumentHandler

{

   private boolean 	debug 	= false;

   private boolean 	stackCreated = false;

   private Stack 	elementStack;

   private Connection	conn = null;

   /** Construct an instance of the handler class 

    *

    * @param conn the JDBC connection to which information is written

    */

   public DBSAXHandler(Connection conn)

   {

      this.conn = conn;

      // Create the stack for keeping track of element context

      // if it doesn't already exist

      if (!stackCreated) {

        elementStack = new Stack();

        stackCreated = true;

      }

   }

   /** SAX Handler that is called at the start of each XML element */

   public void startElement(NSName name, SAXAttrList atts) throws SAXException 

   {

      // Use the methods getQualifiedName(), getLocalName(), getNamespace()

      // and getExpandedName() in NSName interface to get Namespace

      // information.

      String qName;

      String localName;

      String nsName;

      String expName;

      DBSAXElement parentElement;

      DBSAXElement currentElement;

      qName = name.getQualifiedName();

      localName = name.getLocalName();

      nsName = name.getNamespace();

      expName = name.getExpandedName();

      // Get a reference to the parent element for the id

      long parent_id;

      try {

        parentElement = (DBSAXElement)elementStack.peek();

        parent_id = parentElement.getElementID();

      } catch (EmptyStackException e) {

        parent_id = 0;

      }

      // Create the current element representation

      currentElement = new DBSAXElement(conn, localName, parent_id);

      // Add all of the attributes

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

      {

         // Use the methods getQualifiedName(), getLocalName(), getNamespace()

         // and getExpandedName() in SAXAttrList interface to get Namespace

         // information.

         qName = atts.getQualifiedName(i);

         localName = atts.getLocalName(i);

         nsName = atts.getNamespace(i);

         expName = atts.getExpandedName(i);

         // You can get the type and value of the attributes either

         // by index or by the Qualified Name.

         String type = atts.getType(qName);

         String value = atts.getValue(qName);

         currentElement.setAttribute(localName, value);

      }      

      // Add the element to the stack, so that any text data can be 

      // added as it is encountered

      elementStack.push(currentElement);

   }

   /** SAX Handler that is called for each XML text node */

   public void characters(char[] cbuf, int start, int len)

   {

      DBSAXElement currentElement = (DBSAXElement)elementStack.peek();

      currentElement.appendContent(cbuf,start,len);

   }

   /** 

    * SAX Handler that is called for each XML text node that is Ignorable

    * white space

    */

   public void ignorableWhitespace(char[] cbuf, int start, int len)

   {

   }

   /** SAX Handler that is called at the end of each XML element */

   public void endElement(NSName name) throws SAXException 

   {

      // Use the methods getQualifiedName(), getLocalName(), getNamespace()

      // and getExpandedName() in NSName interface to get Namespace

      // information.

      String expName = name.getExpandedName();

      // Get the element from the stack

      DBSAXElement currentElement = (DBSAXElement)elementStack.pop();

      // Write the content of the element to the database

      currentElement.writeContentToDB();

   }

   /** Debug routine */

   private void db(int flag) {

     if (debug) {

       System.err.println("DEBUG POSITION " + flag);

     }

   }   

}