001    // Copyright 2005 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    //     http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry.listener;
016    
017    import org.apache.hivemind.util.Defense;
018    import org.apache.tapestry.IActionListener;
019    import org.apache.tapestry.IComponent;
020    import org.apache.tapestry.IRequestCycle;
021    
022    /**
023     * Terminator implementation for the tapestry.listener.InvokeListener pipeline;
024     * this is what finally turns around and invokes
025     * {@link org.apache.tapestry.IActionListener#actionTriggered(IComponent, IRequestCycle)}.
026     * 
027     * @author Howard M. Lewis Ship
028     * @since 4.0
029     */
030    public class ListenerInvokerTerminator implements ListenerInvoker
031    {
032    
033        /**
034         * @param listener
035         *            to be invoked, may be null if no listener is found (a
036         *            convienience for all the places where listeners are optional)
037         * @param source
038         *            the component generating the listener "event", to be passed to
039         *            the listener. Not generally used, but may not be null.
040         * @param cycle
041         *            the current request cycle, to be passed to the listener.
042         */
043        public void invokeListener(IActionListener listener, IComponent source,
044                IRequestCycle cycle)
045        {
046            Defense.notNull(source, "source");
047            Defense.notNull(cycle, "cycle");
048    
049            if (listener != null)
050                listener.actionTriggered(source, cycle);
051        }
052    
053    }