/*
* Copyright 2005 Joe Walker
*
* Licensed 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.directwebremoting.impl;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import org.directwebremoting.Hub;
import org.directwebremoting.event.DefaultMessageEvent;
import org.directwebremoting.event.MessageEvent;
import org.directwebremoting.event.MessageListener;
/**
* DWR's default implementation of {@link Hub}
* @author Joe Walker [joe at getahead dot ltd dot uk]
*/
public class DefaultHub implements Hub
{
/* (non-Javadoc)
* @see org.directwebremoting.Hub#subscribe(java.lang.String, org.directwebremoting.event.MessageListener)
*/
public void subscribe(String topicName, MessageListener listener)
{
synchronized (subscriptions)
{
Set<MessageListener> listeners = subscriptions.get(topicName);
if (listeners == null)
{
listeners = new HashSet<MessageListener>();
subscriptions.put(topicName, listeners);
}
listeners.add(listener);
}
}
/* (non-Javadoc)
* @see org.directwebremoting.Hub#unsubscribe(java.lang.String, org.directwebremoting.event.MessageListener)
*/
public boolean unsubscribe(String topicName, MessageListener listener)
{
synchronized (subscriptions)
{
boolean unsubscribed = false;
Set<MessageListener> listeners = subscriptions.get(topicName);
if (listeners != null)
{
unsubscribed = listeners.remove(listener);
if (listeners.isEmpty())
{
subscriptions.remove(topicName);
}
}
return unsubscribed;
}
}
/* (non-Javadoc)
* @see org.directwebremoting.Hub#publish(java.lang.String, java.lang.Object)
*/
public void publish(String topicName, Object data)
{
// First clone the list of subscriptions
Set<MessageListener> listeners;
synchronized (subscriptions)
{
Set<MessageListener> current = subscriptions.get(topicName);
if (current == null)
{
return;
}
listeners = new HashSet<MessageListener>();
listeners.addAll(current);
}
// Then tell everyone about the message
for (MessageListener listener : listeners)
{
MessageEvent event;
if (data instanceof MessageEvent)
{
event = (MessageEvent) data;
}
else
{
event = new DefaultMessageEvent(this, data);
}
listener.onMessage(event);
}
}
/**
* The cache of current subscriptions
*/
private final Map<String, Set<MessageListener>> subscriptions = new HashMap<String, Set<MessageListener>>();
}