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
015package org.apache.tapestry.listener;
016
017import org.apache.hivemind.util.Defense;
018import org.apache.tapestry.IActionListener;
019import org.apache.tapestry.IComponent;
020import org.apache.tapestry.IRequestCycle;
021
022/**
023 * Terminator implementation for the tapestry.listener.InvokeListener pipeline; this is what finally
024 * 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 */
030public class ListenerInvokerTerminator implements ListenerInvoker
031{
032
033    /**
034     * @param listener
035     *            to be invoked, may be null if no listener is found (a convienience for all the
036     *            places where listeners are optional)
037     * @param source
038     *            the component generating the listener "event", to be passed to the listener. Not
039     *            generally used, but may not be null.
040     * @param cycle
041     *            the current request cycle, to be passed to the listener.
042     * @param delegate
043     *            the next invoker in the pipeline
044     */
045    public void invokeListener(IActionListener listener, IComponent source, IRequestCycle cycle)
046    {
047        Defense.notNull(source, "source");
048        Defense.notNull(cycle, "cycle");
049
050        if (listener != null)
051            listener.actionTriggered(source, cycle);
052    }
053
054}