Defining a dynamic class in XML

<attribute>
  <name>number</name>
  <javaClass>java.lang.Number</javaClass>
  <defaultValue javaClass="java.lang.Integer">100</defaultValue>
</attribute>

<attribute>
  <name>emptyString</name>
  <javaClass>java.lang.String</javaClass>
  <defaultValue />
</attribute>

<attribute>
  <name>nullString</name>
  <javaClass>java.lang.String</javaClass>
  <defaultValue null="true" />
</attribute>

/**
 * Returns a SAX handler capable of reading the attribute.
 * To avoid an instance of a SAX handler being used simultaneously 
 * by two concurrent threads, this method should either return a new 
 * instance of a SAX handler each time it is called or take advantage of 
 * the java.lang.ThreadLocal class to return a different 
 * instance for each thread.
 * @return A SAX event handler.
 */
  public IlpSAXAttributeValueHandler getSAXHandler() {
    return new IlpSAXPointHandler();
  }

  public static class IlpSAXPointHandler extends IlpSAXAttributeValueHandler {
  protected float x;
  protected float y;
  /**
   * Indicates the beginning of an element.
   * By default, this method only clears the content of the element.
   */
  public void startElement(String namespaceURI,
                           String localName,
                           String qName,
                           Attributes atts) throws SAXException {
    if (localName.equals(finalTag)) {
      x = y = 0.0f;
    }
    super.startElement(namespaceURI,localName,qName,atts);
  }

  /**
   * Notifies the end of an element.
   * When this method is called for the "attribute" element,
   * the <CODE>getAttributeValue</CODE> method is called, the object 
   * is modified accordingly, and parsing continues.
   */
  public void endElement(String namespaceURI,
                         String localName,
                         String qName) throws SAXException {
    if (localName.equals("x")) {
      x = Float.parseFloat(getContent());
    }

    if (localName.equals("y")) {
      y = Float.parseFloat(getContent());
    }

    super.endElement(namespaceURI,localName,qName);
  }

  /**
   * Is called at the end of the "attribute" element.
   */
  protected Object getAttributeValue() {
    Object value = new IlpPoint(x,y);
    return value;
  }

  }

  /**
  * Writes the <CODE>value</CODE> to a SAX ContentHandler.
  * The method translates the object as SAX ContentHandler method calls.
  * @param value The object to write.
  * @param typeConverter The type converter that may be needed to translate
  * values to strings.
  * @param outputHandler The SAX ContentHandler used by this method.
  * @see ilog.cpl.util.IlpTypeConverter#createStringValue(Object,IlpKey)
  */
  public void output(Object value,
    IlpTypeConverter typeConverter,
    ContentHandler outputHandler)
    throws SAXException {
    IlpPoint point = (IlpPoint)value;
    String valueStr = String.valueOf(point.x);
    outputHandler.startElement("","x","x",IlpSAXSerializable.EMPTY_ATTRS);
    outputHandler.characters(valueStr.toCharArray(),0,valueStr.length());
    outputHandler.endElement("","x","x");
    valueStr = String.valueOf(point.y);
    outputHandler.startElement("","y","y",IlpSAXSerializable.EMPTY_ATTRS);
    outputHandler.characters(valueStr.toCharArray(),0,valueStr.length());
    outputHandler.endElement("","y","y");
  }
}