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.activemq.broker.region.policy;
018    
019    import java.util.ArrayList;
020    import java.util.List;
021    import org.apache.activemq.broker.Broker;
022    import org.apache.activemq.broker.ConnectionContext;
023    import org.apache.activemq.broker.region.MessageReference;
024    import org.apache.activemq.broker.region.SubscriptionRecovery;
025    import org.apache.activemq.broker.region.Topic;
026    import org.apache.activemq.command.ActiveMQDestination;
027    import org.apache.activemq.command.Message;
028    import org.apache.activemq.filter.DestinationFilter;
029    
030    /**
031     * This implementation of {@link SubscriptionRecoveryPolicy} will only keep the
032     * last message.
033     * 
034     * @org.apache.xbean.XBean
035     * 
036     */
037    public class LastImageSubscriptionRecoveryPolicy implements SubscriptionRecoveryPolicy {
038    
039        private volatile MessageReference lastImage;
040    
041        public boolean add(ConnectionContext context, MessageReference node) throws Exception {
042            lastImage = node;
043            return true;
044        }
045    
046        public void recover(ConnectionContext context, Topic topic, SubscriptionRecovery sub) throws Exception {
047            // Re-dispatch the last message seen.
048            MessageReference node = lastImage;
049            if (node != null) {
050                sub.addRecoveredMessage(context, node);
051            }
052        }
053    
054        public void start() throws Exception {
055        }
056    
057        public void stop() throws Exception {
058        }
059    
060        public Message[] browse(ActiveMQDestination destination) throws Exception {
061            List<Message> result = new ArrayList<Message>();
062            if (lastImage != null) {
063                DestinationFilter filter = DestinationFilter.parseFilter(destination);
064                if (filter.matches(lastImage.getMessage().getDestination())) {
065                    result.add(lastImage.getMessage());
066                }
067            }
068            return result.toArray(new Message[result.size()]);
069        }
070    
071        public SubscriptionRecoveryPolicy copy() {
072            return new LastImageSubscriptionRecoveryPolicy();
073        }
074        
075        public void setBroker(Broker broker) {        
076        }
077    
078    }