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.broker.region;
018
019import java.io.IOException;
020import java.util.ArrayList;
021import java.util.List;
022import javax.jms.InvalidSelectorException;
023import org.apache.activemq.broker.Broker;
024import org.apache.activemq.broker.ConnectionContext;
025import org.apache.activemq.command.ConsumerInfo;
026import org.apache.activemq.command.MessageAck;
027import org.apache.activemq.filter.MessageEvaluationContext;
028import org.apache.activemq.usage.SystemUsage;
029
030public 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}