queuebrowserendpoint.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

/**
 * Redistribution and use of this software and associated documentation
 * ("Software"), with or without modification, are permitted provided
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 *
 * 1. Redistributions of source code must retain copyright
 *    statements and notices.  Redistributions must also contain a
 *    copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the
 *    above copyright notice, this list of conditions and the
 *    following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. The name "Exolab" must not be used to endorse or promote
 *    products derived from this Software without prior written
 *    permission of Exoffice Technologies.  For written permission,
 *    please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "Exolab"
 *    nor may "Exolab" appear in their names without prior written
 *    permission of Exoffice Technologies. Exolab is a registered
 *    trademark of Exoffice Technologies.
 *
 * 5. Due credit should be given to the Exolab Project
 *    (http://www.exolab.org/).
 *
 * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * EXOFFICE TECHNOLOGIES OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 2001-2003 (C) Exoffice Technologies Inc. All Rights Reserved.
 *
 * $Id: QueueBrowserEndpoint.java,v 1.24 2003/08/13 13:30:54 tanderson Exp $
 *
 * Date         Author  Changes
 * 3/1/2001     jima    Created
 */
package org.exolab.jms.messagemgr;

import java.util.Vector;

import javax.jms.InvalidSelectorException;
import javax.jms.Session;

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

import org.exolab.jms.client.JmsDestination;
import org.exolab.jms.client.JmsQueue;
import org.exolab.jms.message.MessageHandle;
import org.exolab.jms.message.MessageImpl;
import org.exolab.jms.scheduler.Scheduler;
import org.exolab.jms.server.JmsServerSession;


/**
 * A QueueBrowserEndpoint is a QueueListener to a QueueDestinationCache. This
 * enables it to receive all the messages, which it then feeds down to the
 * client side.
 *
 * @version     $Revision: 1.24 $ $Date: 2003/08/13 13:30:54 $
 * @author      <a href="mailto:[e-mail]">Jim Alateras</a>
 */
public class QueueBrowserEndpoint
    extends ConsumerEndpoint
    implements QueueListener {

    /**
     * The destination that this consumer subscribes too
     */
    private QueueDestinationCache _cache = null;

    /**
     * The queue that this endpoint is subscribed too
     */
    private JmsQueue _queue = null;

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


    /**
     * Construct a QueueConsumerEndpoint, that extends ConsumerEndpoint and
     * is used to manage both synchronous and asynchronous message delivery
     * for this consumer.
     *
     * @param session - the owning session
     * @param clientId - uniquely identifies the remote client within session
     * @param destination - 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
     */
    QueueBrowserEndpoint(JmsServerSession session, long clientId,
                         JmsQueue destination, String selector,
                         Scheduler scheduler)
        throws InvalidSelectorException {
        super(session, clientId, selector, scheduler);

        _cache = (QueueDestinationCache)
            DestinationManager.instance().getDestinationCache(destination);
        // if a cache is not active then we need to create one.
        if (_cache == null) {
            _cache = (QueueDestinationCache)
                DestinationManager.instance().createDestinationCache(
                    destination);
        }

        // cache the destination
        _queue = destination;

        // set up the message cache and register itself as a listener to the 
        // cache
        _cache.addQueueListener(this);
        _cache.playbackMessages(this);

    }

    /**
     * Deliver messages in the cache to the consumer.<p>
     * This is not relevant to QueueBrowsers, and thus shouldn't be invoked.
     *
     * @return <code>false</code>
     */
    public boolean deliverMessages() {
        _log.error(
            "QueueBrowserEndpoint.deliverMessages() should never be called",
            new Exception());
        return false;
    }

    // implementation of ConsumerEndpoint.receiveMessage
    public synchronized MessageHandle receiveMessage(long wait) {
        throw new UnsupportedOperationException(
            "Cannot call receiveMessage for QueueBrowser");
    }

    /**
     * Return, at most, count messages from the cache.
     *
     * @param count - the max number of messages to receive
     * @return Vector - number of messages
     */
    public synchronized Vector receiveMessages(int count) {
        Vector messages = new Vector();
        int index = 0;
        while (index < count) {

            // check if we should exit the loop
            if (isStopped() || getMessageCount() == 0) {
                break;
            }

            // remove the first message from the list and check
            // that it is not null. Synchronize the removal of
            // the message but not the sending to the remote
            // consumer
            try {
                MessageHandle handle = removeFirstMessage();

                MessageImpl m = handle.getMessage();
                if (m != null) {
                    // add it to the list of messages to send
                    // but only deliver messsages that satisfy the
                    // selection criteria.
                    if ((_selector == null) ||
                        (_selector.selects(m))) {
                        handle.setClientId(getClientId());
                        messages.addElement(handle);
                        ++index;
                    } else {
                        // drop the message
                    }
                } else {
                    // message may have been consumed in the interim
                }
            } catch (Exception exception) {
                _log.error(exception, exception);
            }
        }

        return messages;
    }


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

    // implementation of ConsumerEndpoint.unregister
    public void unregister() {
        _cache.unregisterConsumer(this);
    }

    // override implementation of ConsumerEndpoint.returnMessage
    public void returnMessage(MessageHandle handle) {
        // no-op at the moment. What happens to a QueueBrowser when
        // a transaction aborts.
    }

    // implementation of QueueListener.onMessage
    public void onMessage(MessageImpl message) {
        // delegate to message added, regardless of whether or not
        // the message is persistent.
        messageAdded(message);
    }

    // override ConsumerEndpoint.setMessageListener
    public void setMessageListener(InternalMessageListener listener) {
        _log.error(
            "QueueBrowserEndpoint.setMessageListener should never be called");
        Thread.currentThread().dumpStack();
    }

    /**
     * Closes this endpoint
     */
    protected void doClose() {
        // unregister from the DestinationCache
        _cache.removeQueueListener(this);
    }

}