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 java.util.Collection;
018    import java.util.Collections;
019    import java.util.HashMap;
020    import java.util.Map;
021    
022    import org.apache.hivemind.ApplicationRuntimeException;
023    import org.apache.hivemind.util.Defense;
024    import org.apache.tapestry.IActionListener;
025    
026    /**
027     * @author Howard M. Lewis Ship
028     * @since 4.0
029     */
030    public class ListenerMapImpl implements ListenerMap
031    {
032        private final Object _target;
033    
034        /**
035         * Keyed on String method name, value is
036         * {@link org.apache.tapestry.listener.ListenerMethodInvoker}.
037         */
038    
039        private final Map _invokers;
040    
041        private final Map _listeners = new HashMap();
042    
043        public ListenerMapImpl(Object target, Map invokers)
044        {
045            Defense.notNull(target, "target");
046            Defense.notNull(invokers, "invokers");
047    
048            _target = target;
049            _invokers = invokers;
050        }
051    
052        public boolean canProvideListener(String name)
053        {
054            return _invokers.containsKey(name);
055        }
056    
057        public synchronized IActionListener getListener(String name)
058        {
059            IActionListener result = (IActionListener) _listeners.get(name);
060    
061            if (result == null)
062            {
063                result = createListener(name);
064                _listeners.put(name, result);
065            }
066    
067            return result;
068        }
069    
070        private IActionListener createListener(String name)
071        {
072            ListenerMethodInvoker invoker = (ListenerMethodInvoker) _invokers.get(name);
073    
074            if (invoker == null)
075                throw new ApplicationRuntimeException(ListenerMessages.objectMissingMethod(
076                        _target,
077                        name), _target, null, null);
078    
079            return new SyntheticListener(_target, invoker);
080        }
081    
082        public Collection getListenerNames()
083        {
084            return Collections.unmodifiableCollection(_invokers.keySet());
085        }
086    }