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.memory.list;
018    
019    import java.util.ArrayList;
020    import java.util.Iterator;
021    import java.util.LinkedList;
022    import java.util.List;
023    import org.apache.activemq.broker.region.MessageReference;
024    import org.apache.activemq.command.ActiveMQDestination;
025    import org.apache.activemq.command.Message;
026    import org.apache.activemq.filter.DestinationFilter;
027    import org.slf4j.Logger;
028    import org.slf4j.LoggerFactory;
029    
030    /**
031     * A simple fixed size {@link MessageList} where there is a single, fixed size
032     * list that all messages are added to for simplicity. Though this will lead to
033     * possibly slow recovery times as many more messages than is necessary will
034     * have to be iterated through for each subscription.
035     * 
036     * 
037     */
038    public class SimpleMessageList implements MessageList {
039        private static final Logger LOG = LoggerFactory.getLogger(SimpleMessageList.class);
040        private final LinkedList<MessageReference> list = new LinkedList<MessageReference>();
041        private int maximumSize = 100 * 64 * 1024;
042        private int size;
043        private final Object lock = new Object();
044    
045        public SimpleMessageList() {
046        }
047    
048        public SimpleMessageList(int maximumSize) {
049            this.maximumSize = maximumSize;
050        }
051    
052        public void add(MessageReference node) {
053            int delta = node.getMessageHardRef().getSize();
054            synchronized (lock) {
055                list.add(node);
056                size += delta;
057                while (size > maximumSize) {
058                    MessageReference evicted = list.removeFirst();
059                    size -= evicted.getMessageHardRef().getSize();
060                }
061            }
062        }
063    
064        public List<MessageReference> getMessages(ActiveMQDestination destination) {
065            return getList();
066        }
067    
068        public Message[] browse(ActiveMQDestination destination) {
069            List<Message> result = new ArrayList<Message>();
070            DestinationFilter filter = DestinationFilter.parseFilter(destination);
071            synchronized (lock) {
072                for (Iterator<MessageReference> i = list.iterator(); i.hasNext();) {
073                    MessageReference ref = i.next();
074                    Message msg;
075                    msg = ref.getMessage();
076                    if (filter.matches(msg.getDestination())) {
077                        result.add(msg);
078                    }
079    
080                }
081            }
082            return result.toArray(new Message[result.size()]);
083        }
084    
085        /**
086         * Returns a copy of the list
087         */
088        public List<MessageReference> getList() {
089            synchronized (lock) {
090                return new ArrayList<MessageReference>(list);
091            }
092        }
093    
094        public int getSize() {
095            synchronized (lock) {
096                return size;
097            }
098        }
099    
100        public void clear() {
101            synchronized (lock) {
102                list.clear();
103                size = 0;
104            }
105        }
106    
107    }