topicconsumerendpoint.java

实现了Jms的服务器源码,支持多种适配器,DB,FTP,支持多种数据库

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 *
 * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
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 *
 * Copyright 2001-2003 (C) Exoffice Technologies Inc. All Rights Reserved.
 *
 * $Id: TopicConsumerEndpoint.java,v 1.40 2003/10/21 14:41:23 tanderson Exp $
 *
 * Date         Author  Changes
 * 3/1/2001     jima    Created
 */
package org.exolab.jms.messagemgr;

import java.sql.Connection;
import java.util.HashMap;
import java.util.Iterator;

import javax.jms.InvalidSelectorException;
import javax.jms.JMSException;
import javax.jms.MessageListener;
import javax.jms.Session;
import javax.transaction.TransactionManager;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.exolab.jms.JMSErrorCodes;
import org.exolab.jms.client.JmsDestination;
import org.exolab.jms.client.JmsTopic;
import org.exolab.jms.message.MessageHandle;
import org.exolab.jms.message.MessageImpl;
import org.exolab.jms.persistence.PersistenceException;
import org.exolab.jms.scheduler.Scheduler;
import org.exolab.jms.server.ClientDisconnectionException;
import org.exolab.jms.server.JmsServerSession;


/**
 * The topic destination cache is specific to a consumer that
 * subscribes to a topic destination. 
 *
 * @version     $Revision: 1.40 $ $Date: 2003/10/21 14:41:23 $
 * @author      <a href="mailto:[e-mail]">Jim Alateras</a>
 */
public class TopicConsumerEndpoint
    extends ConsumerEndpoint
    implements DestinationEventListener {

    /**
     * Maintains a list of TopicDestinationCache that this endpoint subscribes
     * too. A wildcard subscription may point to more than one.
     */
    protected HashMap _caches = new HashMap();

    /**
     * Cache the destination that this endpoint subscribes too
     */
    protected JmsTopic _topic = null;

    /**
     * The maximum number of messages that a dispatch can deliver at any one
     * time
     */
    private final int MAX_MESSAGES = 200;

    /**
     * The logger
     */
    private static final Log _log =
        LogFactory.getLog(TopicConsumerEndpoint.class);


    /**
     * Construct a new <code>TopicConsumerEndpoint</code>.<p/>
     * The destination and selector determine where it will be sourcing
     * its messages from, and scheduler is used to asynchronously deliver
     * messages to the consumer.
     *
     * @param session - the owning session
     * @param clientId - uniquely identifies the remote client within session
     * @param topic - destination that this object was created for
     * @param selector - the selector attached to the consumer, if any.
     * @param scheduler - used to schedule async message delivery.
     * @throws InvalidSelectorException - if the selector is invalid
     * @throws JMSException - for other general exceptions
     */
    TopicConsumerEndpoint(JmsServerSession session, long clientId,
                          JmsTopic topic, String selector, Scheduler scheduler)
        throws InvalidSelectorException, JMSException {
        super(session, clientId, selector, scheduler);

        // register the endpoint with the destination
        DestinationManager destmgr = DestinationManager.instance();
        if (topic != null) {
            _topic = topic;

            if (_topic.isWildCard()) {
                // if the topic is a wild card then we need to retrieve a
                // set of matching destination caches.
                _caches = destmgr.getTopicDestinationCaches(topic);
                // for each cache register this endpoint as a consumer of
                // it's messages. Before doing so register as a destination
                // event listener with the DestinationManager
                destmgr.addDestinationEventListener(this);
                Iterator iter = _caches.values().iterator();
                while (iter.hasNext()) {
                    ((TopicDestinationCache) iter.next()).registerConsumer(this);
                }
            } else {
                // if the topic is not a wildcard then we need to get the
                // destination cache. If one does not exist then we need to
                // create it.
                DestinationCache cache = destmgr.getDestinationCache(topic);
                if (cache == null) {
                    cache = destmgr.createDestinationCache(topic);
                }
                _caches.put(topic, cache);
                cache.registerConsumer(this);
            }
        }
    }

    /**
     * Deliver messages in the cache to the consumer
     *
     * @return <code>true</code> if the endpoint should be rescheduled
     */
    public boolean deliverMessages() {
        boolean reschedule = true;

        for (int index = 0; index < MAX_MESSAGES;) {
            
            // check if we should exit the loop
            if (stopDelivery()) {
                reschedule = false;
                break;
            }

            // Process the first message on the list.
            boolean processed = true;
            MessageHandle handle = removeFirstMessage();
            try {
                if (_selector != null) {
                    MessageImpl m = handle.getMessage();
                    if ((m != null) && _selector.selects(m)) {
                        // this message has been selected by the selector
                        handle.setClientId(getClientId());
                        _listener.onMessage(handle, true);
                        index++;
                    } else {
                        // this message has not been selected
                        handle.destroy();
                    }
                } else {
                    // send the message to the consumer
                    handle.setClientId(getClientId());
                    _listener.onMessage(handle, true);
                    index++;
                }
            } catch (ClientDisconnectionException exception) {
                _listener = null;
                returnMessage(handle);
            } catch (JMSException exception) {
                if (exception.getErrorCode().equals(
                        JMSErrorCodes.FailedToResolveHandle)) {
                    // do not return message back to the cache
                    _log.error("Dropping handle " + handle
                               + " since we cannot resolve it.");
                } else {
                    _log.error(exception, exception);
                    returnMessage(handle);
                }
            } catch (Exception exception) {
                _log.error(exception, exception);
                returnMessage(handle);
            }
        }
        return reschedule;
    }

    // implementation of ConsumerEndpoint.receiveMessage
    public MessageHandle receiveMessage(long wait) {
        synchronized (_waitingForMessageMonitor) {
            MessageHandle handle = receiveNoWait();
            if ((handle == null) &&
                (wait >= 0)) {
                // no message is currently available for this
                // consumer. So set the flag to indicate that
                // the consumer is waiting for a message
                setWaitingForMessage();
            }

            return handle;
        }
    }

    /**
     * Returns the first available message
     */
    public MessageHandle receiveNoWait() {
        MessageHandle handle = null;
        while ((handle = removeFirstMessage()) != null) {
            // make sure we can still get access to the message
            MessageImpl message = handle.getMessage();
            if (message != null) {
                if (_selector == null || _selector.selects(message)) {
                    // got a message which is applicable for the endpoint
                    handle.setClientId(getClientId());
                    break;
                } else {
                    // this message has been filtered out so we can destroy
                    // the handle.
                    handle.destroy();
                }
            }
            handle = null;
        }
        return handle;
    }

    // override ConsumerEndpoint.messageRemoved
    public boolean messageRemoved(MessageImpl message) {

        boolean result = false;

        if (message != null) {
            try {
                MessageHandle handle =
                    MessageHandleFactory.getHandle(this, message);

                // if the message in the main cache then destroy the
                // handle
                if (removeMessage(handle)) {
                    if (handle.getConsumerName() == null) {
                        // @todo - the follwoing is required in order for 
                        // MessageMgr to resolve this endpoint when the 
                        // handle is destroyed. However, its not clear
                        // why topics need to go through MessageMgr at all...
                        handle.setConsumerName(getPersistentId());
                    }
                    handle.destroy();
                    result = true;
                }

            } catch (JMSException exception) {
                _log.error("Failed to remove message from endpoint",
                    exception);
            }
        }

        return result;
    }

    // override ConsumerEndpoint.messageRemoved
    public boolean persistentMessageRemoved(Connection connection,
                                            MessageImpl message)
        throws PersistenceException {

        boolean result = false;

        if (message != null) {
            try {
                PersistentMessageHandle handle = (PersistentMessageHandle)
                    MessageHandleFactory.getHandle(this, message);

                // if the message in the main cache then destroy the handle
                if (removeMessage(handle)) {
                    MessageHandleFactory.destroyPersistentHandle(connection,
                        handle);
                    result = true;
                }

            } catch (JMSException exception) {
                _log.error("Failed to remove persistent message from endpoint",
                    exception);
            }
        }

        return result;
    }

    // implementation of ConsumerEndpoint.getDestination
    public JmsDestination getDestination() {
        return _topic;
    }

    // override ConsumerEndpoint.unregister
    public void unregister() {
        Iterator iter = _caches.values().iterator();
        while (iter.hasNext()) {
            ((TopicDestinationCache) iter.next()).unregisterConsumer(this);
        }
        _caches.clear();
    }

    public void recover() {
        // no-op
    }

    // implementation of DestinationEventListener.destinationAdded
    public void destinationAdded(JmsDestination destination,
                                 DestinationCache cache) {
        if ((destination instanceof JmsTopic) &&
            (_topic.match((JmsTopic) destination)) &&
            (!_caches.containsKey(destination))) {
            synchronized (_caches) {
                _caches.put(destination, cache);
            }

            ((TopicDestinationCache) cache).registerConsumer(this);
            _log.debug(_topic + " registered with " + destination);
        }
    }

    // implementation of DestinationEventListener.destinationRemoved
    public void destinationRemoved(JmsDestination destination,
                                   DestinationCache cache) {
        if ((destination instanceof JmsTopic) &&
            (_caches.containsKey(destination))) {
            synchronized (_caches) {
                _caches.remove(destination);
            }
            _log.debug(_topic + " unregistered with " + destination);
        }
    }

    /**
     * Closes this endpoint
     */
    protected void doClose() {
        // unregister as a destination event listener
        DestinationManager.instance().removeDestinationEventListener(this);
        // unregister from the destination before continuing
        Iterator iter = _caches.values().iterator();
        while (iter.hasNext()) {
            ((TopicDestinationCache) iter.next()).unregisterConsumer(this);
        }
        _caches.clear();
    }

} //-- TopicConsumerEndpoint