listenerset.java

Wicket一个开发Java Web应用程序框架。它使得开发web应用程序变得容易而轻松。 Wicket利用一个POJO data beans组件使得它可以与任何持久层技术相结合。

/*
 * 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.wicket.util.listener;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

/**
 * Holds a set of listeners implementing the IListener tag interface. Subclasses can implement
 * notification methods that cast the listener to the correct subinterface and invoke the
 * appropriate listener method.
 * 
 * @author Jonathan Locke
 */
public abstract class ListenerSet
{
	/** Set of change listeners */
	private final Set listeners = new HashSet();

	/**
	 * Adds a listener to this set of listeners.
	 * 
	 * @param listener
	 *            The listener to add
	 * @return <tt>true</tt> if the set did not already contain the specified listener.
	 */
	public boolean add(final IListener listener)
	{
		return listeners.add(listener);
	}

	/**
	 * Notifies each listener in this set by calling notifyListener.
	 */
	public void notifyListeners()
	{
		// Create a stable copy for iterating over
		final Set copy = new HashSet(listeners);

		// Notify all listeners that the file changed
		for (final Iterator iterator = copy.iterator(); iterator.hasNext();)
		{
			notifyListener((IListener)iterator.next());
		}
	}

	/**
	 * Removes a listener from this set.
	 * 
	 * @param listener
	 *            The listener to remove
	 */
	public void remove(final IListener listener)
	{
		listeners.remove(listener);
	}

	/**
	 * Notifies a listener.
	 * 
	 * @param listener
	 *            The listener to notify
	 */
	protected abstract void notifyListener(IListener listener);
}