abstracttopicconsumerendpoint.java

一个java方面的消息订阅发送的源码

/**
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 * 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
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 * 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].
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 * 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 2005 (C) Exoffice Technologies Inc. All Rights Reserved.
 *
 * $Id: AbstractTopicConsumerEndpoint.java,v 1.1 2005/03/18 03:58:39 tanderson Exp $
 */

package org.exolab.jms.messagemgr;

import java.rmi.RemoteException;
import java.sql.Connection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import javax.jms.InvalidSelectorException;
import javax.jms.JMSException;

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

import org.exolab.jms.client.JmsDestination;
import org.exolab.jms.client.JmsTopic;
import org.exolab.jms.message.MessageImpl;
import org.exolab.jms.persistence.PersistenceException;
import org.exolab.jms.scheduler.Scheduler;
import org.exolab.jms.selector.Selector;
import org.exolab.jms.server.JmsServerSession;


/**
 * A {@link ConsumerEndpoint} for topics.
 *
 * @author <a href="mailto:[e-mail]">Tim Anderson</a>
 * @version $Revision: 1.1 $ $Date: 2005/03/18 03:58:39 $
 */
abstract class AbstractTopicConsumerEndpoint extends AbstractConsumerEndpoint
        implements DestinationEventListener {

    /**
     * Cache of all handles for this consumer.
     */
    private MessageQueue _handles = new MessageQueue();

    /**
     * Maintains a map of TopicDestinationCache that this endpoint subscribes
     * to, keyed on JmsTopic. A wildcard subscription may point to more than
     * one.
     */
    protected Map _caches = Collections.synchronizedMap(new HashMap());

    /**
     * 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(AbstractTopicConsumerEndpoint.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 consumerId the identity of this consumer
     * @param session    the owning session
     * @param topic      the topic to access
     * @param selector   the message selector. May be <code>null</code>
     * @param noLocal    if true, inhibits the delivery of messages published by
     *                   its own connection.
     * @param scheduler  used to schedule asynchronous message delivery.
     * @throws InvalidSelectorException if the selector is invalid
     * @throws JMSException             if the destination caches can't be
     *                                  constructed
     */
    public AbstractTopicConsumerEndpoint(long consumerId,
                                         JmsServerSession session,
                                         JmsTopic topic,
                                         String selector, boolean noLocal,
                                         Scheduler scheduler)
            throws JMSException {
        super(consumerId, session, topic, selector, noLocal, scheduler);
    }

    /**
     * Return the next available message to the client.
     * <p/>
     * The <code>wait</code> parameter indicates how many milliseconds to wait
     * for a message before returning. If <code>wait</code> is <code>0</code>
     * then do not wait. If <code>wait</code> is <code>-1</code> then wait
     * indefinitely for the next message.
     *
     * @param wait number of milliseconds to wait
     * @return the next message or <code>null</code>
     * @throws JMSException for any error
     */
    public MessageHandle receive(long wait) throws JMSException {
        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() throws JMSException {
        MessageHandle handle = null;
        while ((handle = _handles.removeFirst()) != null) {
            // make sure we can still get access to the message
            MessageImpl message = handle.getMessage();
            if (message != null) {
                if (selects(message)) {
                    // got a message which is applicable for the endpoint
                    break;
                } else {
                    // this message has been filtered out so we can destroy
                    // the handle.
                    handle.destroy();
                }
            }
            handle = null;
        }
        return handle;
    }

    /**
     * Return a delivered, but unacknowledged message to the cache.
     *
     * @param handle the handle of the message to return
     */
    public void returnMessage(MessageHandle handle) {
        addMessage(handle);

        // schedule if needed
        schedule();
    }

    /**
     * Return the number of unsent messages in the cache for this consumer.
     *
     * @return the number of unsent messages
     */
    public int getMessageCount() {
        return _handles.size();
    }

    /**
     * This event is called when a non-persistent message is added to the
     * <code>DestinationCache</code>.
     *
     * @param handle  a handle to the message
     * @param message the added message
     * @return <code>true</code> if the listener accepted the message; otherwise
     *         <code>false</ode>
     * @throws JMSException if the listener fails to handle the message
     */
    public boolean messageAdded(MessageHandle handle, MessageImpl message)
            throws JMSException {
        boolean accepted = true;

        // if the 'noLocal' indicator is set, and the message arrived on
        // the same connection, ignore the message
        if (getNoLocal() && message.getConnectionId() == getConnectionId()) {
            accepted = false;
        } else {
            // create a message handle for this consumer
            handle = new TopicConsumerMessageHandle(handle, this);

            if (!_handles.contains(handle)) {
                // if the message is not already in the cache then add it
                addMessage(handle);
                schedule();
            } else {
                accepted = false;
                _log.warn("Endpoint=" + this + " already has message cached: " +
                          handle);
            }
        }
        return accepted;
    }