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;
018    
019    import java.io.IOException;
020    import java.util.List;
021    
022    import javax.jms.JMSException;
023    
024    import org.apache.activemq.broker.region.group.MessageGroupMap;
025    import org.apache.activemq.broker.region.policy.SimpleDispatchSelector;
026    import org.apache.activemq.command.ActiveMQDestination;
027    import org.apache.activemq.command.ActiveMQMessage;
028    import org.apache.activemq.command.ConsumerId;
029    import org.apache.activemq.command.Message;
030    import org.apache.commons.logging.Log;
031    import org.apache.commons.logging.LogFactory;
032    
033    /**
034     * Queue dispatch policy that determines if a message can be sent to a subscription
035     * 
036     * @org.apache.xbean.XBean
037     * @version $Revision$
038     */
039    public class QueueDispatchSelector extends SimpleDispatchSelector {
040        private static final Log LOG = LogFactory.getLog(QueueDispatchSelector.class);
041        private Subscription exclusiveConsumer;
042       
043       
044        /**
045         * @param destination
046         */
047        public QueueDispatchSelector(ActiveMQDestination destination) {
048            super(destination);
049        }
050        
051        public Subscription getExclusiveConsumer() {
052            return exclusiveConsumer;
053        }
054        public void setExclusiveConsumer(Subscription exclusiveConsumer) {
055            this.exclusiveConsumer = exclusiveConsumer;
056        }
057        
058        public boolean isExclusiveConsumer(Subscription s) {
059            return s == this.exclusiveConsumer;
060        }
061        
062           
063        public boolean canSelect(Subscription subscription,
064                MessageReference m) throws Exception {
065           
066            boolean result =  super.canDispatch(subscription, m);
067            if (result && !subscription.isBrowser()) {
068                result = exclusiveConsumer == null
069                        || exclusiveConsumer == subscription;
070                if (result) {
071                    QueueMessageReference node = (QueueMessageReference) m;
072                    // Keep message groups together.
073                    String groupId = node.getGroupID();
074                    int sequence = node.getGroupSequence();
075                    if (groupId != null) {
076                        MessageGroupMap messageGroupOwners = ((Queue) node
077                                .getRegionDestination()).getMessageGroupOwners();
078    
079                        // If we can own the first, then no-one else should own the
080                        // rest.
081                        if (sequence == 1) {
082                            assignGroup(subscription, messageGroupOwners, node,groupId);
083                        }else {
084        
085                            // Make sure that the previous owner is still valid, we may
086                            // need to become the new owner.
087                            ConsumerId groupOwner;
088        
089                            groupOwner = messageGroupOwners.get(groupId);
090                            if (groupOwner == null) {
091                                assignGroup(subscription, messageGroupOwners, node,groupId);
092                            } else {
093                                if (groupOwner.equals(subscription.getConsumerInfo().getConsumerId())) {
094                                    // A group sequence < 1 is an end of group signal.
095                                    if (sequence < 0) {
096                                        messageGroupOwners.removeGroup(groupId);
097                                    }
098                                } else {
099                                    result = false;
100                                }
101                            }
102                        }
103                    }
104                }
105            }
106            return result;
107        }
108        
109        protected void assignGroup(Subscription subs,MessageGroupMap messageGroupOwners, MessageReference n, String groupId) throws IOException {
110            messageGroupOwners.put(groupId, subs.getConsumerInfo().getConsumerId());
111            Message message = n.getMessage();
112            if (message instanceof ActiveMQMessage) {
113                ActiveMQMessage activeMessage = (ActiveMQMessage)message;
114                try {
115                    activeMessage.setBooleanProperty("JMSXGroupFirstForConsumer", true, false);
116                } catch (JMSException e) {
117                    LOG.warn("Failed to set boolean header: " + e, e);
118                }
119            }
120        }
121        
122        
123        
124        
125    }