001    // Copyright 2004, 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.hivemind.impl;
016    
017    import java.util.HashSet;
018    import java.util.Iterator;
019    import java.util.Set;
020    
021    import org.apache.commons.logging.Log;
022    import org.apache.commons.logging.LogFactory;
023    import org.apache.hivemind.ShutdownCoordinator;
024    import org.apache.hivemind.events.RegistryShutdownListener;
025    import org.apache.hivemind.util.EventListenerList;
026    
027    /**
028     * Manages a list of objects that implement the
029     * {@link org.apache.hivemind.events.RegistryShutdownListener} interface.
030     * 
031     * @author Howard Lewis Ship
032     */
033    public final class ShutdownCoordinatorImpl implements ShutdownCoordinator
034    {
035        private final Log _log;
036    
037        private Set alreadyShutdown;
038    
039        public ShutdownCoordinatorImpl()
040        {
041            this(LogFactory.getLog(ShutdownCoordinatorImpl.class));
042        }
043    
044        public ShutdownCoordinatorImpl(Log log)
045        {
046            _log = log;        
047        }
048    
049        private EventListenerList _listenerList;
050    
051        public synchronized void addRegistryShutdownListener(
052                RegistryShutdownListener s)
053        {
054            if (_listenerList == null)
055                _listenerList = new EventListenerList();
056    
057            _listenerList.addListener(s);
058        }
059    
060        public synchronized void removeRegistryShutdownListener(
061                RegistryShutdownListener s)
062        {
063            if (_listenerList != null)
064                _listenerList.removeListener(s);
065        }
066    
067        public void shutdown()
068        {
069            if (_listenerList == null)
070                return;
071    
072            Iterator i = _listenerList.getListeners();
073    
074            _listenerList = null;
075    
076            while (i.hasNext())
077            {
078                RegistryShutdownListener s = (RegistryShutdownListener) i.next();
079    
080                shutdown(s);
081            }
082    
083            _listenerList = null;
084        }
085    
086        private void shutdown(RegistryShutdownListener s)
087        {
088            if (alreadyShutdown == null)
089            {
090                alreadyShutdown = new HashSet();
091            }
092            final Long id = new Long(System.identityHashCode(s));
093            if (!alreadyShutdown.contains(id))
094            {
095                try
096                {
097                    s.registryDidShutdown();
098                }
099                catch (RuntimeException ex)
100                {
101                    _log.error(ImplMessages.shutdownCoordinatorFailure(s, ex), ex);
102                }
103                finally
104                {
105                    alreadyShutdown.add(id);
106                }
107            }
108        }
109    
110    }