http://xml.apache.org/commons/components/external/: xml-commons provides an Apache-hosted set of DOM, SAX, and JAXP interfaces for use in other xml-based projects. Our hope is that we can standardize on both a common version and packaging scheme for these critical XML standards interfaces to make the lives of both our developers and users easier. The External Components portion of xml-commons contains interfaces that are defined by external standards organizations. For DOM, that's the W3C; for SAX it's David Megginson and sax.sourceforge.net; for JAXP it's Sun. 
/*
 * Copyright (c) 2004 World Wide Web Consortium,
 *
 * (Massachusetts Institute of Technology, European Research Consortium for
 * Informatics and Mathematics, Keio University). All Rights Reserved. This
 * work is distributed under the W3C(r) Software License [1] in the hope that
 * it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * [1] http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231
 */

package org.w3c.dom;


When associating an object to a key on a node using 
Node.setUserData() the application can provide a handler 
that gets called when the node the object is associated to is being 
cloned, imported, or renamed. This can be used by the application to 
implement various behaviors regarding the data it associates to the DOM 
nodes. This interface defines that handler. 

See also the Document Object Model (DOM) Level 3 Core Specification.

Since:DOM Level 3
/**
 * When associating an object to a key on a node using 
 * <code>Node.setUserData()</code> the application can provide a handler 
 * that gets called when the node the object is associated to is being 
 * cloned, imported, or renamed. This can be used by the application to 
 * implement various behaviors regarding the data it associates to the DOM 
 * nodes. This interface defines that handler. 
 * <p>See also the <a href='http://www.w3.org/TR/2004/REC-DOM-Level-3-Core-20040407'>Document Object Model (DOM) Level 3 Core Specification</a>.
 * @since DOM Level 3
 */
public interface UserDataHandler {
    // OperationType
    
The node is cloned, using Node.cloneNode().

/**
     * The node is cloned, using <code>Node.cloneNode()</code>.
     */
    public static final short NODE_CLONED               = 1;
    
The node is imported, using Document.importNode().

/**
     * The node is imported, using <code>Document.importNode()</code>.
     */
    public static final short NODE_IMPORTED             = 2;
    
The node is deleted.

Note: This may not be supported or may not be reliable in 
certain environments, such as Java, where the implementation has no 
real control over when objects are actually deleted.

/**
     * The node is deleted.
     * <p ><b>Note:</b> This may not be supported or may not be reliable in 
     * certain environments, such as Java, where the implementation has no 
     * real control over when objects are actually deleted.
     */
    public static final short NODE_DELETED              = 3;
    
The node is renamed, using Document.renameNode().

/**
     * The node is renamed, using <code>Document.renameNode()</code>.
     */
    public static final short NODE_RENAMED              = 4;
    
The node is adopted, using Document.adoptNode().

/**
     * The node is adopted, using <code>Document.adoptNode()</code>.
     */
    public static final short NODE_ADOPTED              = 5;

    
This method is called whenever the node for which this handler is 
registered is imported or cloned.

 DOM applications must not raise exceptions in a 
UserDataHandler. The effect of throwing exceptions from 
the handler is DOM implementation dependent. 

Params:
  • operation – Specifies the type of operation that is being 
  performed on the node.
  • key – Specifies the key for which this handler is being called.
  • data – Specifies the data for which this handler is being called.
  • src – Specifies the node being cloned, adopted, imported, or 
  renamed. This is null when the node is being deleted.
  • dst – Specifies the node newly created if any, or 
  null.
/**
     * This method is called whenever the node for which this handler is 
     * registered is imported or cloned.
     * <br> DOM applications must not raise exceptions in a 
     * <code>UserDataHandler</code>. The effect of throwing exceptions from 
     * the handler is DOM implementation dependent. 
     * @param operation Specifies the type of operation that is being 
     *   performed on the node.
     * @param key Specifies the key for which this handler is being called. 
     * @param data Specifies the data for which this handler is being called. 
     * @param src Specifies the node being cloned, adopted, imported, or 
     *   renamed. This is <code>null</code> when the node is being deleted.
     * @param dst Specifies the node newly created if any, or 
     *   <code>null</code>.
     */
    public void handle(short operation, 
                       String key, 
                       Object data, 
                       Node src, 
                       Node dst);

}