dispatchhandler.java

Java的面向对象数据库系统的源代码

/*
 * Copyright 2001 (C) MetaStuff, Ltd. All Rights Reserved.
 * 
 * This software is open source. 
 * See the bottom of this file for the licence.
 * 
 * $Id: DispatchHandler.java,v 1.2 2003/06/10 16:18:34 per_nyfelt Exp $
 */

package org.dom4j.io;

import org.dom4j.Element;
import org.dom4j.ElementHandler;
import org.dom4j.ElementPath;

import java.util.ArrayList;
import java.util.HashMap;

/** <p><code>DispatchHandler</code> implements the <code>ElementHandler</code>
  * interface and provides a means to register multiple <code>ElementHandler</code>
  * instances to be used by an event based processor.  This is a special
  * <code>ElementHandler</code> in that it's <b>onStart</b> and <b>onEnd</b>
  * implementation methods are called for every element encountered during
  * the parse.  It then delegates to other <code>ElementHandler</code> instances
  * registered with it to process the elements encountered.
  *
  * @author <a href="mailto:[e-mail]">Dave White</a>
  * @version $Revision: 1.2 $
  */

class DispatchHandler implements ElementHandler
{
    /** Whether the parser is at the root element or not */
    private boolean        atRoot;
    
    /** The current path in the XML tree (i.e. /a/b/c) */
    private String         path;
    
    /** maintains a stack of previously encountered paths */
    private ArrayList      pathStack;
    
    /** maintains a stack of previously encountered handlers */
    private ArrayList      handlerStack;
    
    /** <code>HashMap</code> maintains the mapping between element paths and handlers */
    private HashMap        handlers;
    
    /** <code>ElementHandler</code> to use by default for element paths with no handlers registered */
    private ElementHandler defaultHandler;
    
    public DispatchHandler()
    {
        atRoot          = true;
        path            = "/";
        pathStack       = new ArrayList();
        handlerStack    = new ArrayList();
        handlers        = new HashMap();
    }
    
    /** Adds the <code>ElementHandler</code> to be called when the 
      * specified path is encounted.
      *
      * @param path is the path to be handled
      * @param handler is the <code>ElementHandler</code> to be called
      * by the event based processor.
      */
    public void addHandler(String path, ElementHandler handler)
    {
        handlers.put(path, handler);   
    }
    
    /** Removes the <code>ElementHandler</code> from the event based
      * processor, for the specified path.
      *
      * @param path is the path to remove the <code>ElementHandler</code> for.
      */
    public ElementHandler removeHandler(String path)
    {
        return (ElementHandler)handlers.remove(path);   
    }
    
    /** When multiple <code>ElementHandler</code> instances have been 
      * registered, this will set a default <code>ElementHandler</code>
      * to be called for any path which does <b>NOT</b> have a handler
      * registered.
      * @param handler is the <code>ElementHandler</code> to be called
      * by the event based processor.
      */
    public void setDefaultHandler(ElementHandler handler)
    {
        defaultHandler = handler;
    }
    
    /**
     * Used to remove all the Element Handlers and return things back to the way
     * they were when object was created.
     */
    public void resetHandlers() {
        atRoot          = true;
        path            = "/";
        pathStack.clear();
        handlerStack.clear();
        handlers.clear();
	defaultHandler=null;
    }

    /** @return the current path for the parse */
    public String getPath() { return path; }
    
    // The following methods implement the ElementHandler interface
    
    public void onStart(ElementPath elementPath)
    {
        Element element = elementPath.getCurrent();
        // Save the location of the last (i.e. parent) path 
        pathStack.add(path);
        // Calculate the new path
        if (atRoot)
        {
            path = path + element.getName();   
            atRoot = false;
        }
        else 
        {
            path = path + "/" + element.getName();
        }
        
        if ((handlers != null) && (handlers.containsKey(path)))
        {
            // The current node has a handler associated with it.
            // Find the handler and save it on the handler stack.
            ElementHandler handler = (ElementHandler)handlers.get(path);
            handlerStack.add(handler);
            // Call the handlers onStart method.
            handler.onStart(elementPath);
        }
        else
        {
            // No handler is associated with this node, so use the
            // defaultHandler it it exists.
            if (handlerStack.isEmpty() && (defaultHandler != null))
            {
                defaultHandler.onStart(elementPath);
            }
        }
    }
    
    public void onEnd(ElementPath elementPath)
    {   
        if ((handlers != null) && (handlers.containsKey(path)))
        {
            // This node has a handler associated with it.
            // Find the handler and pop it from the handler stack.
            ElementHandler handler = (ElementHandler)handlers.get(path);
            handlerStack.remove( handlerStack.size() - 1 );
            // Call the handlers onEnd method
            handler.onEnd(elementPath);
        }
        else
        {
            // No handler is associated with this node, so use the
            // defaultHandler it it exists.
            if (handlerStack.isEmpty() && (defaultHandler != null))
            {
                defaultHandler.onEnd(elementPath);
            }
        }
        // Set path back to its parent
        path = (String)pathStack.remove( pathStack.size() - 1 );
    }   
}




/*
 * Redistribution and use of this software and associated documentation
 * ("Software"), with or without modification, are permitted provided
 * that the following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright
 *    statements and notices.  Redistributions must also contain a
 *    copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the
 *    above copyright notice, this list of conditions and the
 *    following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. The name "DOM4J" must not be used to endorse or promote
 *    products derived from this Software without prior written
 *    permission of MetaStuff, Ltd.  For written permission,
 *    please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "DOM4J"
 *    nor may "DOM4J" appear in their names without prior written
 *    permission of MetaStuff, Ltd. DOM4J is a registered
 *    trademark of MetaStuff, Ltd.
 *
 * 5. Due credit should be given to the DOM4J Project
 *    (http://dom4j.org/).
 *
 * THIS SOFTWARE IS PROVIDED BY METASTUFF, LTD. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * METASTUFF, LTD. OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 2001 (C) MetaStuff, Ltd. All Rights Reserved.
 *
 * $Id: DispatchHandler.java,v 1.2 2003/06/10 16:18:34 per_nyfelt Exp $
 */