/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
package org.apache.mina.handler.demux;
import java.util.Collections;
import java.util.Hashtable;
import java.util.Map;
import java.util.Set;
import org.apache.mina.common.IoHandler;
import org.apache.mina.common.IoHandlerAdapter;
import org.apache.mina.common.IoSession;
import org.apache.mina.util.IdentityHashSet;
/**
* A {@link IoHandler} that demuxes <code>messageReceived</code> events
* to the appropriate {@link MessageHandler}.
* <p>
* You can freely register and deregister {@link MessageHandler}s using
* {@link #addMessageHandler(Class, MessageHandler)} and
* {@link #removeMessageHandler(Class)}.
* </p>
* <p>
* When <code>message</code> is received through a call to
* {@link #messageReceived(IoSession, Object)} the class of the
* <code>message</code> object will be used to find a {@link MessageHandler} for
* that particular message type. If no {@link MessageHandler} instance can be
* found for the immediate class (i.e. <code>message.getClass()</code>) the
* interfaces implemented by the immediate class will be searched in depth-first
* order. If no match can be found for any of the interfaces the search will be
* repeated recursively for the superclass of the immediate class
* (i.e. <code>message.getClass().getSuperclass()</code>).
* </p>
* <p>
* Consider the following type hierarchy (<code>Cx</code> are classes while
* <code>Ix</code> are interfaces):
* <pre>
* C3 - I7 - I9
* | | /\
* | I8 I3 I4
* |
* C2 - I5 - I6
* |
* C1 - I1 - I2 - I4
* | |
* | I3
* Object
* </pre>
* When <code>message</code> is of type <code>C3</code> this hierarchy will be
* searched in the following order:
* <code>C3, I7, I8, I9, I3, I4, C2, I5, I6, C1, I1, I2, I3, I4, Object</code>.
* </p>
* <p>
* For efficiency searches will be cached. Calls to
* {@link #addMessageHandler(Class, MessageHandler)} and
* {@link #removeMessageHandler(Class)} clear this cache.
* </p>
*
* @author The Apache Directory Project (mina-dev@directory.apache.org)
* @version $Rev: 495082 $, $Date: 2007-01-11 10:38:48 +0900 (목, 11 1월 2007) $
*/
public class DemuxingIoHandler extends IoHandlerAdapter
{
private final Map findHandlerCache = new Hashtable();
private final Map type2handler = new Hashtable();
/**
* Creates a new instance with no registered {@link MessageHandler}s.
*/
public DemuxingIoHandler()
{
}
/**
* Registers a {@link MessageHandler} that receives the messages of
* the specified <code>type</code>.
*
* @return the old handler if there is already a registered handler for
* the specified <tt>type</tt>. <tt>null</tt> otherwise.
*/
public MessageHandler addMessageHandler( Class type, MessageHandler handler )
{
findHandlerCache.clear();
return ( MessageHandler ) type2handler.put( type, handler );
}
/**
* Deregisters a {@link MessageHandler} that receives the messages of
* the specified <code>type</code>.
*
* @return the removed handler if successfully removed. <tt>null</tt> otherwise.
*/
public MessageHandler removeMessageHandler( Class type )
{
findHandlerCache.clear();
return ( MessageHandler ) type2handler.remove( type );
}
/**
* Returns the {@link MessageHandler} which is registered to process
* the specified <code>type</code>.
*/
public MessageHandler getMessageHandler( Class type )
{
return ( MessageHandler ) type2handler.get( type );
}
/**
* Returns the {@link Map} which contains all messageType-{@link MessageHandler}
* pairs registered to this handler.
*/
public Map getMessageHandlerMap()
{
return Collections.unmodifiableMap( type2handler );
}
/**
* Forwards the received events into the appropriate {@link MessageHandler}
* which is registered by {@link #addMessageHandler(Class, MessageHandler)}.
*/
public void messageReceived( IoSession session, Object message ) throws Exception
{
MessageHandler handler = findHandler( message.getClass() );
if( handler != null )
{
handler.messageReceived( session, message );
}
else
{
throw new UnknownMessageTypeException(
"No message handler found for message: " + message );
}
}
protected MessageHandler findHandler( Class type )
{
return findHandler( type, null );
}
private MessageHandler findHandler( Class type, Set triedClasses )
{
MessageHandler handler = null;
if( triedClasses != null && triedClasses.contains( type ) )
return null;
/*
* Try the cache first.
*/
handler = ( MessageHandler ) findHandlerCache.get( type );
if( handler != null )
return handler;
/*
* Try the registered handlers for an immediate match.
*/
handler = ( MessageHandler ) type2handler.get( type );
if( handler == null )
{
/*
* No immediate match could be found. Search the type's interfaces.
*/
if( triedClasses == null )
triedClasses = new IdentityHashSet();
triedClasses.add( type );
Class[] interfaces = type.getInterfaces();
for( int i = 0; i < interfaces.length; i ++ )
{
handler = findHandler( interfaces[ i ], triedClasses );
if( handler != null )
break;
}
}
if( handler == null )
{
/*
* No match in type's interfaces could be found. Search the
* superclass.
*/
Class superclass = type.getSuperclass();
if( superclass != null )
handler = findHandler( superclass );
}
/*
* Make sure the handler is added to the cache. By updating the cache
* here all the types (superclasses and interfaces) in the path which
* led to a match will be cached along with the immediate message type.
*/
if( handler != null )
findHandlerCache.put( type, handler );
return handler;
}
}