001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.servicemix.store.memory;
018    
019    import java.io.IOException;
020    import java.util.concurrent.ConcurrentHashMap;
021    import java.util.concurrent.ConcurrentMap;
022    
023    import org.apache.commons.logging.Log;
024    import org.apache.commons.logging.LogFactory;
025    import org.apache.servicemix.id.IdGenerator;
026    
027    /**
028     * {@link MemoryStore} which removes entries from the store after the specified timeout
029     * to free memory.
030     */
031    public class TimeoutMemoryStore extends MemoryStore {
032    
033        private static final Log LOG = LogFactory.getLog(TimeoutMemoryStore.class);
034        private ConcurrentMap<String, Entry> datas = new ConcurrentHashMap<String, Entry>();
035        private final long timeout;
036    
037        protected TimeoutMemoryStore(IdGenerator idGenerator, long timeout) {
038            super(idGenerator);
039            this.timeout = timeout;
040        }
041        
042        /**
043         * {@inheritDoc}
044         */
045        public void store(String id, Object data) throws IOException {
046            LOG.debug("Storing object with id: " + id);
047            datas.put(id, new Entry(data));
048        }
049        
050        /**
051         * {@inheritDoc}
052         * 
053         * Before attempting to load the object, all data older than the specified timeout will first be 
054         * removed from the store.
055         */
056        public Object load(String id) throws IOException {
057            evict();
058            LOG.debug("Loading object with id:" + id);
059            Entry entry = datas.remove(id);
060            return entry == null ? null : entry.data;
061        }
062        
063        private void evict() {
064            long now = System.currentTimeMillis();
065            for (String key : datas.keySet()) {
066                long age = now - datas.get(key).time;
067                if (age > timeout) {
068                    LOG.debug("Removing object with id " + key + " from store after " + age + " ms");
069                    datas.remove(key);
070                }
071            }
072        }
073    
074        /*
075         * A single store entry
076         */
077        private final class Entry {
078            final long time = System.currentTimeMillis();
079            final Object data;
080            
081            private Entry(Object data) {
082                this.data = data;
083            }
084        }
085    }