SAXTraverser.java

/*
 * SAXTraverser.java
 *
 * Created on February 9, 2001, 3:02 PM
 */

package org.freehep.xml.util;
import org.xml.sax.*;
import org.xml.sax.helpers.DefaultHandler;

/**
 * A utility for working with SAX parsers. A heirarchy of SAXTraversers can be
 * used to maintain state while parsing an XML file.
 * @author  tonyj
 * @version $Id: SAXTraverser.java 8584 2006-08-10 23:06:37Z duns $
 */
public class SAXTraverser extends DefaultHandler
{
    /**
     * Attach an XMLReader to this traverser. Registers this SAXTraverser as the
     * content handler for the reader.
     */
   public void setReader(XMLReader reader)
   {
      this.parser = reader;
      reader.setContentHandler(this);
   }
   public void startElement(String namespaceURI,String localName,String qName,Attributes attrs) throws SAXException
   {
      qName = qName.intern();
      SAXTraverser newHandler = handleElement(qName,attrs);
      if (newHandler != this)
      {
         newHandler.handleElementAttributes(attrs);
         newHandler.previous = this;
         newHandler.parser = parser;
         parser.setContentHandler(newHandler);
      }
      else stack++;
      
   }
   public void endElement(String namespaceURI,String localName,String qName) throws SAXException
   {
      if (stack == 0)
      {
         handleEndElement(localName);
         previous.handleSubElement(this);
         parser.setContentHandler(previous);
      }
      else stack--;
   }
    /**
     * Override to handle node attributes
     */
   protected void handleElementAttributes(Attributes atts) throws SAXException
   {
   }
    /**
     * Override this to handle the end of an element
     */
   protected void handleEndElement(String name) throws SAXException
   {
   }
    /**
     * Override this to be notified of sub nodes of the current node
     */
   protected void handleSubElement(SAXTraverser sub) throws SAXException
   {
   }
    /**
     * Override this to handle the start of new sub elements
     * Return the SAXTraverser to be used for the sub node, or <code>this</code> to continue
     * using the current traverser.
     * @return The SAXTraverser to be used as the content handler for the sub node 
     */
   protected SAXTraverser handleElement(String name, Attributes attrs) throws SAXException
   {
      throw new BadXMLException("Unhandled element "+name);
   }
   /**
    * Utility routine to convert a String to a boolean
    */
   public boolean toBoolean(String value) throws BadXMLException
   {
      if      (value.equalsIgnoreCase("true")) return true;
      else if (value.equalsIgnoreCase("false")) return false;
      else throw new BadXMLException("Bad boolean value "+value);
   }
   /**
    * Utility routine to convert a String to a double
    */
   public double toDouble(String value) throws SAXException
   {
      try
      {
         return new Double(value).doubleValue();
      }
      catch (Throwable x)
      {
         throw new BadXMLException("Bad double value "+value);
      }
   }
   /**
    * Utility routine to convert a String to a float
    */
   public float toFloat(String value) throws SAXException
   {
      try
      {
         return Float.parseFloat(value);
      }
      catch (Throwable x)
      {
         throw new BadXMLException("Bad float value "+value);
      }
   }
   /**
    * Utility routine to convert a String to an int
    */
   public int toInt(String value) throws SAXException
   {
      try
      {
         return Integer.parseInt(value);
      }
      catch (Throwable x)
      {
         throw new BadXMLException("Bad integer value "+value);
      }
   }
   /**
    * Utility routine to convert a String to a short
    */
   public short toShort(String value) throws SAXException
   {
      try
      {
         return Short.parseShort(value);
      }
      catch (Throwable x)
      {
         throw new BadXMLException("Bad short value "+value);
      }
   }
   /**
    * Utility routine to convert a String to a long
    */
   public long toLong(String value) throws SAXException
   {
      try
      {
         return Long.parseLong(value);
      }
      catch (Throwable x)
      {
         throw new BadXMLException("Bad long value "+value);
      }
   }
   /**
    * Utility routine to convert a String to a byte
    */
   public byte toByte(String value) throws SAXException
   {
      try
      {
         return Byte.parseByte(value);
      }
      catch (Throwable x)
      {
         throw new BadXMLException("Bad byte value "+value);
      }
   }
   private SAXTraverser previous;
   private XMLReader parser;
   private int stack = 0;
}