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.ArrayList;
021    import java.util.List;
022    import javax.jms.InvalidSelectorException;
023    import org.apache.activemq.broker.Broker;
024    import org.apache.activemq.broker.ConnectionContext;
025    import org.apache.activemq.command.ConsumerInfo;
026    import org.apache.activemq.command.MessageAck;
027    import org.apache.activemq.filter.MessageEvaluationContext;
028    import org.apache.activemq.usage.SystemUsage;
029    
030    public class QueueBrowserSubscription extends QueueSubscription {
031    
032        int queueRefs;
033        boolean browseDone;
034        boolean destinationsAdded;
035    
036        public QueueBrowserSubscription(Broker broker,SystemUsage usageManager, ConnectionContext context, ConsumerInfo info)
037            throws InvalidSelectorException {
038            super(broker,usageManager, context, info);
039        }
040    
041        protected boolean canDispatch(MessageReference node) {
042            return !((QueueMessageReference)node).isAcked();
043        }
044    
045        public synchronized String toString() {
046            return "QueueBrowserSubscription:" + " consumer=" + info.getConsumerId() + ", destinations="
047                   + destinations.size() + ", dispatched=" + dispatched.size() + ", delivered="
048                   + this.prefetchExtension + ", pending=" + getPendingQueueSize();
049        }
050    
051        synchronized public void destinationsAdded() throws Exception {
052            destinationsAdded = true;
053            checkDone();
054        }
055    
056        private void checkDone() throws Exception {
057            if( !browseDone && queueRefs == 0 && destinationsAdded) {
058                browseDone=true;
059                add(QueueMessageReference.NULL_MESSAGE);
060            }
061        }
062    
063        public boolean matches(MessageReference node, MessageEvaluationContext context) throws IOException {
064            return !browseDone && super.matches(node, context);
065        }
066    
067        /**
068         * Since we are a browser we don't really remove the message from the queue.
069         */
070        protected void acknowledge(ConnectionContext context, final MessageAck ack, final MessageReference n)
071            throws IOException {
072            if (info.isNetworkSubscription()) {
073                    super.acknowledge(context, ack, n);
074            }
075        }
076    
077        synchronized public void incrementQueueRef() {
078            queueRefs++;        
079        }
080    
081        synchronized public void decrementQueueRef() throws Exception {
082            queueRefs--;
083            checkDone();
084        }
085    
086    
087        @Override
088        public List<MessageReference> remove(ConnectionContext context, Destination destination) throws Exception {
089            super.remove(context, destination);
090            // there's no unacked messages that needs to be redelivered
091            // in case of browser
092            return new ArrayList<MessageReference>();
093        }
094    }