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.tapestry.services.impl;
016    
017    import java.util.HashMap;
018    import java.util.LinkedList;
019    import java.util.List;
020    import java.util.Map;
021    
022    import org.apache.tapestry.event.ResetEventListener;
023    import org.apache.tapestry.services.ObjectPool;
024    
025    /**
026     * Implementation of the {@link org.apache.tapestry.services.ObjectPool} interface.
027     * 
028     * <p>
029     * This ia a minimal implementation, one that has no concept of automatically removing
030     * unused pooled objects. Eventually, it will also register for notifications about
031     * general cache cleaning.
032     *
033     * @author Howard Lewis Ship
034     * @since 4.0
035     */
036    public class ObjectPoolImpl implements ObjectPool, ResetEventListener
037    {
038        /**
039         * Pool of Lists (of pooled objects), keyed on arbitrary key.
040         */
041        private Map _pool = new HashMap();
042    
043        public synchronized Object get(Object key)
044        {
045            List pooled = (List) _pool.get(key);
046    
047            if (pooled == null || pooled.isEmpty())
048                return null;
049    
050            return pooled.remove(0);
051        }
052    
053        public synchronized void store(Object key, Object value)
054        {
055            List pooled = (List) _pool.get(key);
056    
057            if (pooled == null)
058            {
059                pooled = new LinkedList();
060                _pool.put(key, pooled);
061            }
062    
063            pooled.add(value);
064        }
065    
066        public synchronized void resetEventDidOccur()
067        {
068            _pool.clear();
069        }
070    
071    }