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 */
017package org.apache.activemq.memory.list;
018
019import java.util.ArrayList;
020import java.util.Iterator;
021import java.util.LinkedList;
022import java.util.List;
023import org.apache.activemq.broker.region.MessageReference;
024import org.apache.activemq.command.ActiveMQDestination;
025import org.apache.activemq.command.Message;
026import org.apache.activemq.filter.DestinationFilter;
027import org.slf4j.Logger;
028import 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 */
038public 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}