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 javax.jms.InvalidSelectorException;
021    import org.apache.activemq.broker.Broker;
022    import org.apache.activemq.broker.ConnectionContext;
023    import org.apache.activemq.command.ConsumerInfo;
024    import org.apache.activemq.command.MessageAck;
025    import org.apache.activemq.filter.MessageEvaluationContext;
026    import org.apache.activemq.usage.SystemUsage;
027    
028    public class QueueBrowserSubscription extends QueueSubscription {
029    
030        int queueRefs;
031        boolean browseDone;
032        boolean destinationsAdded;
033    
034        public QueueBrowserSubscription(Broker broker,SystemUsage usageManager, ConnectionContext context, ConsumerInfo info)
035            throws InvalidSelectorException {
036            super(broker,usageManager, context, info);
037        }
038    
039        protected boolean canDispatch(MessageReference node) {
040            return !((QueueMessageReference)node).isAcked();
041        }
042    
043        public synchronized String toString() {
044            return "QueueBrowserSubscription:" + " consumer=" + info.getConsumerId() + ", destinations="
045                   + destinations.size() + ", dispatched=" + dispatched.size() + ", delivered="
046                   + this.prefetchExtension + ", pending=" + getPendingQueueSize();
047        }
048    
049        synchronized public void destinationsAdded() throws Exception {
050            destinationsAdded = true;
051            checkDone();
052        }
053    
054        private void checkDone() throws Exception {
055            if( !browseDone && queueRefs == 0 && destinationsAdded) {
056                browseDone=true;
057                add(QueueMessageReference.NULL_MESSAGE);
058            }
059        }
060    
061        public boolean matches(MessageReference node, MessageEvaluationContext context) throws IOException {
062            return !browseDone && super.matches(node, context);
063        }
064    
065        /**
066         * Since we are a browser we don't really remove the message from the queue.
067         */
068        protected void acknowledge(ConnectionContext context, final MessageAck ack, final MessageReference n)
069            throws IOException {
070            if (info.isNetworkSubscription()) {
071                    super.acknowledge(context, ack, n);
072            }
073        }
074    
075        synchronized public void incrementQueueRef() {
076            queueRefs++;        
077        }
078    
079        synchronized public void decrementQueueRef() throws Exception {
080            queueRefs--;
081            checkDone();
082        }
083    
084    }