Package org.apache.activemq

Source Code of org.apache.activemq.ActiveMQMessageConsumer

/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.activemq;

import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

import javax.jms.IllegalStateException;
import javax.jms.InvalidDestinationException;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;

import org.apache.activemq.command.ActiveMQDestination;
import org.apache.activemq.command.ActiveMQMessage;
import org.apache.activemq.command.ActiveMQTempDestination;
import org.apache.activemq.command.ConsumerId;
import org.apache.activemq.command.ConsumerInfo;
import org.apache.activemq.command.MessageAck;
import org.apache.activemq.command.MessageDispatch;
import org.apache.activemq.command.MessagePull;
import org.apache.activemq.management.JMSConsumerStatsImpl;
import org.apache.activemq.management.StatsCapable;
import org.apache.activemq.management.StatsImpl;
import org.apache.activemq.selector.SelectorParser;
import org.apache.activemq.thread.Scheduler;
import org.apache.activemq.transaction.Synchronization;
import org.apache.activemq.util.Callback;
import org.apache.activemq.util.IntrospectionSupport;
import org.apache.activemq.util.JMSExceptionSupport;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
* A client uses a <CODE>MessageConsumer</CODE> object to receive messages
* from a destination. A <CODE> MessageConsumer</CODE> object is created by
* passing a <CODE>Destination</CODE> object to a message-consumer creation
* method supplied by a session.
* <P>
* <CODE>MessageConsumer</CODE> is the parent interface for all message
* consumers.
* <P>
* A message consumer can be created with a message selector. A message selector
* allows the client to restrict the messages delivered to the message consumer
* to those that match the selector.
* <P>
* A client may either synchronously receive a message consumer's messages or
* have the consumer asynchronously deliver them as they arrive.
* <P>
* For synchronous receipt, a client can request the next message from a message
* consumer using one of its <CODE> receive</CODE> methods. There are several
* variations of <CODE>receive</CODE> that allow a client to poll or wait for
* the next message.
* <P>
* For asynchronous delivery, a client can register a
* <CODE>MessageListener</CODE> object with a message consumer. As messages
* arrive at the message consumer, it delivers them by calling the
* <CODE>MessageListener</CODE>'s<CODE>
* onMessage</CODE> method.
* <P>
* It is a client programming error for a <CODE>MessageListener</CODE> to
* throw an exception.
*
* @version $Revision: 1.22 $
* @see javax.jms.MessageConsumer
* @see javax.jms.QueueReceiver
* @see javax.jms.TopicSubscriber
* @see javax.jms.Session
*/
public class ActiveMQMessageConsumer implements MessageAvailableConsumer, StatsCapable, ActiveMQDispatcher {

    private static final Log LOG = LogFactory.getLog(ActiveMQMessageConsumer.class);

    protected final ActiveMQSession session;
    protected final ConsumerInfo info;

    // These are the messages waiting to be delivered to the client
    private final MessageDispatchChannel unconsumedMessages = new MessageDispatchChannel();

    // The are the messages that were delivered to the consumer but that have
    // not been acknowledged. It's kept in reverse order since we
    // Always walk list in reverse order. Only used when session is client ack.
    private final LinkedList<MessageDispatch> deliveredMessages = new LinkedList<MessageDispatch>();
    private int deliveredCounter;
    private int additionalWindowSize;
    private long redeliveryDelay;
    private int ackCounter;
    private int dispatchedCount;
    private MessageListener messageListener;
    private JMSConsumerStatsImpl stats;

    private final String selector;
    private boolean synchronizationRegistered;
    private AtomicBoolean started = new AtomicBoolean(false);

    private MessageAvailableListener availableListener;

    private RedeliveryPolicy redeliveryPolicy;
    private boolean optimizeAcknowledge;
    private AtomicBoolean deliveryingAcknowledgements = new AtomicBoolean();
    private ExecutorService executorService;
    private MessageTransformer transformer;
    private boolean clearDispatchList;

    /**
     * Create a MessageConsumer
     *
     * @param session
     * @param dest
     * @param name
     * @param selector
     * @param prefetch
     * @param maximumPendingMessageCount TODO
     * @param noLocal
     * @param browser
     * @param dispatchAsync
     * @param messageListener
     * @throws JMSException
     */
    public ActiveMQMessageConsumer(ActiveMQSession session, ConsumerId consumerId, ActiveMQDestination dest,
            String name, String selector, int prefetch,
            int maximumPendingMessageCount, boolean noLocal, boolean browser,
            boolean dispatchAsync, MessageListener messageListener) throws JMSException {
        if (dest == null) {
            throw new InvalidDestinationException("Don't understand null destinations");
        } else if (dest.getPhysicalName() == null) {
            throw new InvalidDestinationException("The destination object was not given a physical name.");
        } else if (dest.isTemporary()) {
            String physicalName = dest.getPhysicalName();

            if (physicalName == null) {
                throw new IllegalArgumentException("Physical name of Destination should be valid: " + dest);
            }

            String connectionID = session.connection.getConnectionInfo().getConnectionId().getValue();

            if (physicalName.indexOf(connectionID) < 0) {
                throw new InvalidDestinationException(
                                                      "Cannot use a Temporary destination from another Connection");
            }

            if (session.connection.isDeleted(dest)) {
                throw new InvalidDestinationException(
                                                      "Cannot use a Temporary destination that has been deleted");
            }
        }

        this.session = session;
        this.redeliveryPolicy = session.connection.getRedeliveryPolicy();
        setTransformer(session.getTransformer());

        this.info = new ConsumerInfo(consumerId);
        this.info.setExclusive(this.session.connection.isExclusiveConsumer());
        this.info.setSubscriptionName(name);
        this.info.setPrefetchSize(prefetch);
        this.info.setCurrentPrefetchSize(prefetch);
        this.info.setMaximumPendingMessageLimit(maximumPendingMessageCount);
        this.info.setNoLocal(noLocal);
        this.info.setDispatchAsync(dispatchAsync);
        this.info.setRetroactive(this.session.connection.isUseRetroactiveConsumer());
        this.info.setSelector(null);

        // Allows the options on the destination to configure the consumerInfo
        if (dest.getOptions() != null) {
            Map<String, String> options = new HashMap<String, String>(dest.getOptions());
            IntrospectionSupport.setProperties(this.info, options, "consumer.");
        }

        this.info.setDestination(dest);
        this.info.setBrowser(browser);
        if (selector != null && selector.trim().length() != 0) {
            // Validate the selector
            new SelectorParser().parse(selector);
            this.info.setSelector(selector);
            this.selector = selector;
        } else if (info.getSelector() != null) {
            // Validate the selector
            new SelectorParser().parse(this.info.getSelector());
            this.selector = this.info.getSelector();
        } else {
            this.selector = null;
        }

        this.stats = new JMSConsumerStatsImpl(session.getSessionStats(), dest);
        this.optimizeAcknowledge = session.connection.isOptimizeAcknowledge() && session.isAutoAcknowledge()
                                   && !info.isBrowser();
        this.info.setOptimizedAcknowledge(this.optimizeAcknowledge);

        if (messageListener != null) {
            setMessageListener(messageListener);
        }
        try {
            this.session.addConsumer(this);
            this.session.syncSendPacket(info);
        } catch (JMSException e) {
            this.session.removeConsumer(this);
            throw e;
        }

        if (session.connection.isStarted()) {
            start();
        }
    }

    public StatsImpl getStats() {
        return stats;
    }

    public JMSConsumerStatsImpl getConsumerStats() {
        return stats;
    }

    public RedeliveryPolicy getRedeliveryPolicy() {
        return redeliveryPolicy;
    }

    /**
     * Sets the redelivery policy used when messages are redelivered
     */
    public void setRedeliveryPolicy(RedeliveryPolicy redeliveryPolicy) {
        this.redeliveryPolicy = redeliveryPolicy;
    }

    public MessageTransformer getTransformer() {
        return transformer;
    }

    /**
     * Sets the transformer used to transform messages before they are sent on
     * to the JMS bus
     */
    public void setTransformer(MessageTransformer transformer) {
        this.transformer = transformer;
    }

    /**
     * @return Returns the value.
     */
    protected ConsumerId getConsumerId() {
        return info.getConsumerId();
    }

    /**
     * @return the consumer name - used for durable consumers
     */
    protected String getConsumerName() {
        return this.info.getSubscriptionName();
    }

    /**
     * @return true if this consumer does not accept locally produced messages
     */
    protected boolean isNoLocal() {
        return info.isNoLocal();
    }

    /**
     * Retrieve is a browser
     *
     * @return true if a browser
     */
    protected boolean isBrowser() {
        return info.isBrowser();
    }

    /**
     * @return ActiveMQDestination
     */
    protected ActiveMQDestination getDestination() {
        return info.getDestination();
    }

    /**
     * @return Returns the prefetchNumber.
     */
    public int getPrefetchNumber() {
        return info.getPrefetchSize();
    }

    /**
     * @return true if this is a durable topic subscriber
     */
    public boolean isDurableSubscriber() {
        return info.getSubscriptionName() != null && info.getDestination().isTopic();
    }

    /**
     * Gets this message consumer's message selector expression.
     *
     * @return this message consumer's message selector, or null if no message
     *         selector exists for the message consumer (that is, if the message
     *         selector was not set or was set to null or the empty string)
     * @throws JMSException if the JMS provider fails to receive the next
     *                 message due to some internal error.
     */
    public String getMessageSelector() throws JMSException {
        checkClosed();
        return selector;
    }

    /**
     * Gets the message consumer's <CODE>MessageListener</CODE>.
     *
     * @return the listener for the message consumer, or null if no listener is
     *         set
     * @throws JMSException if the JMS provider fails to get the message
     *                 listener due to some internal error.
     * @see javax.jms.MessageConsumer#setMessageListener(javax.jms.MessageListener)
     */
    public MessageListener getMessageListener() throws JMSException {
        checkClosed();
        return this.messageListener;
    }

    /**
     * Sets the message consumer's <CODE>MessageListener</CODE>.
     * <P>
     * Setting the message listener to null is the equivalent of unsetting the
     * message listener for the message consumer.
     * <P>
     * The effect of calling <CODE>MessageConsumer.setMessageListener</CODE>
     * while messages are being consumed by an existing listener or the consumer
     * is being used to consume messages synchronously is undefined.
     *
     * @param listener the listener to which the messages are to be delivered
     * @throws JMSException if the JMS provider fails to receive the next
     *                 message due to some internal error.
     * @see javax.jms.MessageConsumer#getMessageListener
     */
    public void setMessageListener(MessageListener listener) throws JMSException {
        checkClosed();
        if (info.getPrefetchSize() == 0) {
            throw new JMSException(
                                   "Illegal prefetch size of zero. This setting is not supported for asynchronous consumers please set a value of at least 1");
        }
        this.messageListener = listener;
        if (listener != null) {
            boolean wasRunning = session.isRunning();
            if (wasRunning) {
                session.stop();
            }

            session.redispatch(this, unconsumedMessages);

            if (wasRunning) {
                session.start();
            }

        }
    }

    public MessageAvailableListener getAvailableListener() {
        return availableListener;
    }

    /**
     * Sets the listener used to notify synchronous consumers that there is a
     * message available so that the {@link MessageConsumer#receiveNoWait()} can
     * be called.
     */
    public void setAvailableListener(MessageAvailableListener availableListener) {
        this.availableListener = availableListener;
    }

    /**
     * Used to get an enqueued message from the unconsumedMessages list. The
     * amount of time this method blocks is based on the timeout value. - if
     * timeout==-1 then it blocks until a message is received. - if timeout==0
     * then it it tries to not block at all, it returns a message if it is
     * available - if timeout>0 then it blocks up to timeout amount of time.
     * Expired messages will consumed by this method.
     *
     * @throws JMSException
     * @return null if we timeout or if the consumer is closed.
     */
    private MessageDispatch dequeue(long timeout) throws JMSException {
        try {
            long deadline = 0;
            if (timeout > 0) {
                deadline = System.currentTimeMillis() + timeout;
            }
            while (true) {
                MessageDispatch md = unconsumedMessages.dequeue(timeout);
                if (md == null) {
                    if (timeout > 0 && !unconsumedMessages.isClosed()) {
                        timeout = Math.max(deadline - System.currentTimeMillis(), 0);
                    } else {
                        return null;
                    }
                } else if (md.getMessage() == null) {
                    return null;
                } else if (md.getMessage().isExpired()) {
                    if (LOG.isDebugEnabled()) {
                        LOG.debug(getConsumerId() + " received expired message: " + md);
                    }
                    beforeMessageIsConsumed(md);
                    afterMessageIsConsumed(md, true);
                    if (timeout > 0) {
                        timeout = Math.max(deadline - System.currentTimeMillis(), 0);
                    }
                } else {
                    if (LOG.isDebugEnabled()) {
                        LOG.debug(getConsumerId() + " received message: " + md);
                    }
                    return md;
                }
            }
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            throw JMSExceptionSupport.create(e);
        }
    }

    /**
     * Receives the next message produced for this message consumer.
     * <P>
     * This call blocks indefinitely until a message is produced or until this
     * message consumer is closed.
     * <P>
     * If this <CODE>receive</CODE> is done within a transaction, the consumer
     * retains the message until the transaction commits.
     *
     * @return the next message produced for this message consumer, or null if
     *         this message consumer is concurrently closed
     */
    public Message receive() throws JMSException {
        checkClosed();
        checkMessageListener();

        sendPullCommand(0);
        MessageDispatch md = dequeue(-1);
        if (md == null) {
            return null;
        }

        beforeMessageIsConsumed(md);
        afterMessageIsConsumed(md, false);

        return createActiveMQMessage(md);
    }

    /**
     * @param md
     * @return
     */
    private ActiveMQMessage createActiveMQMessage(final MessageDispatch md) throws JMSException {
        ActiveMQMessage m = (ActiveMQMessage)md.getMessage().copy();
        if (transformer != null) {
            Message transformedMessage = transformer.consumerTransform(session, this, m);
            if (transformedMessage != null) {
                m = ActiveMQMessageTransformation.transformMessage(transformedMessage, session.connection);
            }
        }
        if (session.isClientAcknowledge()) {
            m.setAcknowledgeCallback(new Callback() {
                public void execute() throws Exception {
                    session.checkClosed();
                    session.acknowledge();
                }
            });
        }
        return m;
    }

    /**
     * Receives the next message that arrives within the specified timeout
     * interval.
     * <P>
     * This call blocks until a message arrives, the timeout expires, or this
     * message consumer is closed. A <CODE>timeout</CODE> of zero never
     * expires, and the call blocks indefinitely.
     *
     * @param timeout the timeout value (in milliseconds), a time out of zero
     *                never expires.
     * @return the next message produced for this message consumer, or null if
     *         the timeout expires or this message consumer is concurrently
     *         closed
     */
    public Message receive(long timeout) throws JMSException {
        checkClosed();
        checkMessageListener();
        if (timeout == 0) {
            return this.receive();

        }

        sendPullCommand(timeout);
        while (timeout > 0) {

            MessageDispatch md;
            if (info.getPrefetchSize() == 0) {
                md = dequeue(-1); // We let the broker let us know when we
                // timeout.
            } else {
                md = dequeue(timeout);
            }

            if (md == null) {
                return null;
            }

            beforeMessageIsConsumed(md);
            afterMessageIsConsumed(md, false);
            return createActiveMQMessage(md);
        }
        return null;
    }

    /**
     * Receives the next message if one is immediately available.
     *
     * @return the next message produced for this message consumer, or null if
     *         one is not available
     * @throws JMSException if the JMS provider fails to receive the next
     *                 message due to some internal error.
     */
    public Message receiveNoWait() throws JMSException {
        checkClosed();
        checkMessageListener();
        sendPullCommand(-1);

        MessageDispatch md;
        if (info.getPrefetchSize() == 0) {
            md = dequeue(-1); // We let the broker let us know when we
            // timeout.
        } else {
            md = dequeue(0);
        }

        if (md == null) {
            return null;
        }

        beforeMessageIsConsumed(md);
        afterMessageIsConsumed(md, false);
        return createActiveMQMessage(md);
    }

    /**
     * Closes the message consumer.
     * <P>
     * Since a provider may allocate some resources on behalf of a <CODE>
     * MessageConsumer</CODE>
     * outside the Java virtual machine, clients should close them when they are
     * not needed. Relying on garbage collection to eventually reclaim these
     * resources may not be timely enough.
     * <P>
     * This call blocks until a <CODE>receive</CODE> or message listener in
     * progress has completed. A blocked message consumer <CODE>receive </CODE>
     * call returns null when this message consumer is closed.
     *
     * @throws JMSException if the JMS provider fails to close the consumer due
     *                 to some internal error.
     */
    public void close() throws JMSException {
        if (!unconsumedMessages.isClosed()) {
            dispose();
            this.session.asyncSendPacket(info.createRemoveCommand());
        }
    }

    void clearMessagesInProgress() {
        // we are called from inside the transport reconnection logic
        // which involves us clearing all the connections' consumers
        // dispatch lists and clearing them
        // so rather than trying to grab a mutex (which could be already
        // owned by the message listener calling the send) we will just set
        // a flag so that the list can be cleared as soon as the
        // dispatch thread is ready to flush the dispatch list
        clearDispatchList = true;
    }

    void deliverAcks() {
        MessageAck ack = null;
        if (deliveryingAcknowledgements.compareAndSet(false, true)) {
            if (this.optimizeAcknowledge) {
                if (!deliveredMessages.isEmpty()) {
                    MessageDispatch md = deliveredMessages.getFirst();
                    ack = new MessageAck(md, MessageAck.STANDARD_ACK_TYPE, deliveredMessages.size());
                    deliveredMessages.clear();
                    ackCounter = 0;
                }
            }
            if (ack != null) {
                final MessageAck ackToSend = ack;
                if (executorService == null) {
                    executorService = Executors.newSingleThreadExecutor();
                }
                executorService.submit(new Runnable() {
                    public void run() {
                        try {
                            session.asyncSendPacket(ackToSend);
                        } catch (JMSException e) {
                            LOG.error(getConsumerId() + " failed to delivered acknowledgements", e);
                        } finally {
                            deliveryingAcknowledgements.set(false);
                        }
                    }
                });
            } else {
                deliveryingAcknowledgements.set(false);
            }
        }
    }

    public void dispose() throws JMSException {
        if (!unconsumedMessages.isClosed()) {
           
//            if ( !deliveredMessages.isEmpty() ) {
//                // We need to let the broker know how many times that message
//                // was rolled back.
//                rollbackCounter++;
//                MessageDispatch lastMd = deliveredMessages.get(0);
//            }

            // Do we have any acks we need to send out before closing?
            // Ack any delivered messages now. (session may still
            // commit/rollback the acks).
            // only processes optimized acknowledgements
            deliverAcks();
            if (executorService != null) {
                executorService.shutdown();
                try {
                    executorService.awaitTermination(60, TimeUnit.SECONDS);
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }
            if (session.isTransacted() || session.isDupsOkAcknowledge()) {
                acknowledge();
            }
            if (session.isClientAcknowledge()) {
                if (!this.info.isBrowser()) {
                    // rollback duplicates that aren't acknowledged
                    for (MessageDispatch old : deliveredMessages) {
                        session.connection.rollbackDuplicate(this, old.getMessage());
                    }
                }
            }
            deliveredMessages.clear();
            List<MessageDispatch> list = unconsumedMessages.removeAll();
            if (!this.info.isBrowser()) {
                for (MessageDispatch old : list) {
                    // ensure we don't filter this as a duplicate
                    session.connection.rollbackDuplicate(this, old.getMessage());
                }
            }
            unconsumedMessages.close();
            this.session.removeConsumer(this);
        }
    }

    /**
     * @throws IllegalStateException
     */
    protected void checkClosed() throws IllegalStateException {
        if (unconsumedMessages.isClosed()) {
            throw new IllegalStateException("The Consumer is closed");
        }
    }

    /**
     * If we have a zero prefetch specified then send a pull command to the
     * broker to pull a message we are about to receive
     */
    protected void sendPullCommand(long timeout) throws JMSException {
        if (info.getPrefetchSize() == 0 && unconsumedMessages.isEmpty()) {
            MessagePull messagePull = new MessagePull();
            messagePull.configure(info);
            messagePull.setTimeout(timeout);
            session.asyncSendPacket(messagePull);
        }
    }

    protected void checkMessageListener() throws JMSException {
        session.checkMessageListener();
    }

    protected void setOptimizeAcknowledge(boolean value) {
        if (optimizeAcknowledge && !value) {
            deliverAcks();
        }
        optimizeAcknowledge = value;
    }

    protected void setPrefetchSize(int prefetch) {
        deliverAcks();
        this.info.setCurrentPrefetchSize(prefetch);
    }

    private void beforeMessageIsConsumed(MessageDispatch md) throws JMSException {
        md.setDeliverySequenceId(session.getNextDeliveryId());
        if (!session.isDupsOkAcknowledge()) {
            deliveredMessages.addFirst(md);
            if (session.isTransacted()) {
                ackLater(md, MessageAck.DELIVERED_ACK_TYPE);
            }
        }
    }

    private void afterMessageIsConsumed(MessageDispatch md, boolean messageExpired) throws JMSException {
        if (unconsumedMessages.isClosed()) {
            return;
        }
        if (messageExpired) {
            ackLater(md, MessageAck.DELIVERED_ACK_TYPE);
        } else {
            stats.onMessage();
            if (session.isTransacted()) {
                // Do nothing.
            } else if (session.isAutoAcknowledge()) {
                if (!deliveredMessages.isEmpty()) {
                    if (optimizeAcknowledge) {
                        if (deliveryingAcknowledgements.compareAndSet(false, true)) {
                            ackCounter++;
                            if (ackCounter >= (info.getCurrentPrefetchSize() * .65)) {
                                MessageAck ack = new MessageAck(md, MessageAck.STANDARD_ACK_TYPE,
                                                                deliveredMessages.size());
                                session.asyncSendPacket(ack);
                                ackCounter = 0;
                                deliveredMessages.clear();
                            }
                            deliveryingAcknowledgements.set(false);
                        }
                    } else {
                        MessageAck ack = new MessageAck(md, MessageAck.STANDARD_ACK_TYPE, deliveredMessages
                            .size());
                        session.asyncSendPacket(ack);
                        deliveredMessages.clear();
                    }
                }
            } else if (session.isDupsOkAcknowledge()) {
                ackLater(md, MessageAck.STANDARD_ACK_TYPE);
            } else if (session.isClientAcknowledge()) {
                ackLater(md, MessageAck.DELIVERED_ACK_TYPE);
            } else {
                throw new IllegalStateException("Invalid session state.");
            }
        }
    }

    private void ackLater(MessageDispatch md, byte ackType) throws JMSException {

        // Don't acknowledge now, but we may need to let the broker know the
        // consumer got the message
        // to expand the pre-fetch window
        if (session.isTransacted()) {
            session.doStartTransaction();
            if (!synchronizationRegistered) {
                synchronizationRegistered = true;
                session.getTransactionContext().addSynchronization(new Synchronization() {
                    public void beforeEnd() throws Exception {
                        acknowledge();
                        synchronizationRegistered = false;
                    }

                    public void afterCommit() throws Exception {
                        commit();
                        synchronizationRegistered = false;
                    }

                    public void afterRollback() throws Exception {
                        rollback();
                        synchronizationRegistered = false;
                    }
                });
            }
        }

        // The delivered message list is only needed for the recover method
        // which is only used with client ack.
        deliveredCounter++;
        if ((0.5 * info.getPrefetchSize()) <= (deliveredCounter - additionalWindowSize)) {
            MessageAck ack = new MessageAck(md, ackType, deliveredCounter);
            ack.setTransactionId(session.getTransactionContext().getTransactionId());
            session.asyncSendPacket(ack);
            additionalWindowSize = deliveredCounter;

            // When using DUPS ok, we do a real ack.
            if (ackType == MessageAck.STANDARD_ACK_TYPE) {
                deliveredCounter = 0;
                additionalWindowSize = 0;
            }
        }
    }

    /**
     * Acknowledge all the messages that have been delivered to the client upto
     * this point.
     *
     * @throws JMSException
     */
    public void acknowledge() throws JMSException {
        if (deliveredMessages.isEmpty()) {
            return;
        }

        // Acknowledge the last message.
        MessageDispatch lastMd = deliveredMessages.get(0);
        MessageAck ack = new MessageAck(lastMd, MessageAck.STANDARD_ACK_TYPE, deliveredMessages.size());
        if (session.isTransacted()) {
            session.doStartTransaction();
            ack.setTransactionId(session.getTransactionContext().getTransactionId());
        }
        session.asyncSendPacket(ack);

        // Adjust the counters
        deliveredCounter -= deliveredMessages.size();
        additionalWindowSize = Math.max(0, additionalWindowSize - deliveredMessages.size());

        if (!session.isTransacted()) {
            deliveredMessages.clear();
        }
    }

    public void commit() throws JMSException {
        deliveredMessages.clear();
        redeliveryDelay = 0;
    }

    public void rollback() throws JMSException {
        synchronized (unconsumedMessages.getMutex()) {
            if (optimizeAcknowledge) {
                // remove messages read but not acked at the broker yet through
                // optimizeAcknowledge
                if (!this.info.isBrowser()) {
                    for (int i = 0; (i < deliveredMessages.size()) && (i < ackCounter); i++) {
                        // ensure we don't filter this as a duplicate
                        MessageDispatch md = deliveredMessages.removeLast();
                        session.connection.rollbackDuplicate(this, md.getMessage());
                    }
                }
            }
            if (deliveredMessages.isEmpty()) {
                return;
            }

            // Only increase the redlivery delay after the first redelivery..
            MessageDispatch lastMd = deliveredMessages.getFirst();
            if (lastMd.getMessage().getRedeliveryCounter() > 0) {
                redeliveryDelay = redeliveryPolicy.getRedeliveryDelay(redeliveryDelay);
            }

            for (Iterator iter = deliveredMessages.iterator(); iter.hasNext();) {
                MessageDispatch md = (MessageDispatch)iter.next();
                md.getMessage().onMessageRolledBack();
            }

            if (redeliveryPolicy.getMaximumRedeliveries() != RedeliveryPolicy.NO_MAXIMUM_REDELIVERIES
                && lastMd.getMessage().getRedeliveryCounter() > redeliveryPolicy.getMaximumRedeliveries()) {
                // We need to NACK the messages so that they get sent to the
                // DLQ.
                // Acknowledge the last message.
               
                MessageAck ack = new MessageAck(lastMd, MessageAck.POSION_ACK_TYPE, deliveredMessages.size());
                session.asyncSendPacket(ack);
                // ensure we don't filter this as a duplicate
                session.connection.rollbackDuplicate(this, lastMd.getMessage());
                // Adjust the window size.
                additionalWindowSize = Math.max(0, additionalWindowSize - deliveredMessages.size());
                redeliveryDelay = 0;
            } else {
               
                MessageAck ack = new MessageAck(lastMd, MessageAck.REDELIVERED_ACK_TYPE, deliveredMessages.size());
                session.asyncSendPacket(ack);

                // stop the delivery of messages.
                unconsumedMessages.stop();

                for (Iterator iter = deliveredMessages.iterator(); iter.hasNext();) {
                    MessageDispatch md = (MessageDispatch)iter.next();
                    unconsumedMessages.enqueueFirst(md);
                }

                if (redeliveryDelay > 0) {
                    // Start up the delivery again a little later.
                    Scheduler.executeAfterDelay(new Runnable() {
                        public void run() {
                            try {
                                if (started.get()) {
                                    start();
                                }
                            } catch (JMSException e) {
                                session.connection.onAsyncException(e);
                            }
                        }
                    }, redeliveryDelay);
                } else {
                    start();
                }

            }
            deliveredCounter -= deliveredMessages.size();
            deliveredMessages.clear();
        }
        if (messageListener != null) {
            session.redispatch(this, unconsumedMessages);
        }
    }

    public void dispatch(MessageDispatch md) {
        MessageListener listener = this.messageListener;
        try {
            synchronized (unconsumedMessages.getMutex()) {
                if (clearDispatchList) {
                    // we are reconnecting so lets flush the in progress
                    // messages
                    clearDispatchList = false;
                    List<MessageDispatch> list = unconsumedMessages.removeAll();
                    if (!this.info.isBrowser()) {
                        for (MessageDispatch old : list) {
                            // ensure we don't filter this as a duplicate
                            session.connection.rollbackDuplicate(this, old.getMessage());
                        }
                    }
                }
                if (!unconsumedMessages.isClosed()) {
                    if (this.info.isBrowser() || !session.connection.isDuplicate(this, md.getMessage())) {
                        if (listener != null && unconsumedMessages.isRunning()) {
                            ActiveMQMessage message = createActiveMQMessage(md);
                            beforeMessageIsConsumed(md);
                            try {
                                boolean expired = message.isExpired();
                                if (!expired) {
                                    listener.onMessage(message);
                                }
                                afterMessageIsConsumed(md, expired);
                            } catch (RuntimeException e) {
                                if (session.isDupsOkAcknowledge() || session.isAutoAcknowledge()) {
                                    // Redeliver the message
                                } else {
                                    // Transacted or Client ack: Deliver the
                                    // next message.
                                    afterMessageIsConsumed(md, false);
                                }
                                LOG.error(getConsumerId() + " Exception while processing message: " + e, e);
                            }
                        } else {
                            unconsumedMessages.enqueue(md);
                            if (availableListener != null) {
                                availableListener.onMessageAvailable(this);
                            }
                        }
                    } else {
                        // ignore duplicate
                        if (LOG.isDebugEnabled()) {
                            LOG.debug(getConsumerId() + " Ignoring Duplicate: " + md.getMessage());
                        }
                        ackLater(md, MessageAck.STANDARD_ACK_TYPE);
                    }
                }
            }
            if (++dispatchedCount % 1000 == 0) {
                dispatchedCount = 0;
                Thread.yield();
            }
        } catch (Exception e) {
            session.connection.onAsyncException(e);
        }
    }

    public int getMessageSize() {
        return unconsumedMessages.size();
    }

    public void start() throws JMSException {
        if (unconsumedMessages.isClosed()) {
            return;
        }
        started.set(true);
        unconsumedMessages.start();
        session.executor.wakeup();
    }

    public void stop() {
        started.set(false);
        unconsumedMessages.stop();
    }

    public String toString() {
        return "ActiveMQMessageConsumer { value=" + info.getConsumerId() + ", started=" + started.get()
               + " }";
    }

    /**
     * Delivers a message to the message listener.
     *
     * @return
     * @throws JMSException
     */
    public boolean iterate() {
        MessageListener listener = this.messageListener;
        if (listener != null) {
            MessageDispatch md = unconsumedMessages.dequeueNoWait();
            if (md != null) {
                try {
                    ActiveMQMessage message = createActiveMQMessage(md);
                    beforeMessageIsConsumed(md);
                    listener.onMessage(message);
                    afterMessageIsConsumed(md, false);
                } catch (JMSException e) {
                    session.connection.onAsyncException(e);
                }
                return true;
            }
        }
        return false;
    }

    public boolean isInUse(ActiveMQTempDestination destination) {
        return info.getDestination().equals(destination);
    }

}
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