abstractdestinationcache.java

一个java方面的消息订阅发送的源码

/**
 * Redistribution and use of this software and associated documentation
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 * that the following conditions are met:
 *
 * 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 2001-2005 (C) Exoffice Technologies Inc. All Rights Reserved.
 *
 * $Id: AbstractDestinationCache.java,v 1.1 2005/03/18 03:58:38 tanderson Exp $
 */
package org.exolab.jms.messagemgr;

import java.sql.Connection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
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.lease.LeaseEventListenerIfc;
import org.exolab.jms.lease.LeaseManager;
import org.exolab.jms.message.MessageImpl;
import org.exolab.jms.persistence.PersistenceException;
import org.exolab.jms.persistence.DatabaseService;
import org.exolab.jms.persistence.SQLHelper;


/**
 * Abstract implementation of the {@link DestinationCache} interface
 *
 * @author <a href="mailto:[e-mail]">Tim Anderson</a>
 * @version $Revision: 1.1 $ $Date: 2005/03/18 03:58:38 $
 */
public abstract class AbstractDestinationCache implements DestinationCache,
        LeaseEventListenerIfc {

    /**
     * The destination to cache messages for.
     */
    private final JmsDestination _destination;

    /**
     * The message cache for this destination.
     */
    private DefaultMessageCache _cache = new DefaultMessageCache();

    /**
     * The set of consumers that have subscribed to this cache, keyed on id
     */
    private Map _consumers = Collections.synchronizedMap(new HashMap());

    /**
     * A map of String -> MessageLease objects, representing the active
     * leases keyed on JMSMessageID.
     */
    private HashMap _leases = new HashMap();

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


    /**
     * Construct a new <code>AbstractDestinationCache</code>, for a temporary
     * destination.
     *
     * @param destination the destination to cache messages for
     */
    public AbstractDestinationCache(JmsDestination destination) {
        if (destination == null) {
            throw new IllegalArgumentException(
                    "Argument 'destination' is null");
        }
        if (destination.getPersistent()) {
            throw new IllegalArgumentException(
                    "Argument 'destination' refers to a persistent destination");
        }
        _destination = destination;

        // register this with the message manager
        MessageMgr.instance().addEventListener(getDestination(), this);
    }

    /**
     * Construct a new <code>DestinationCache</code>, for a persistent
     * destination.
     *
     * @param destination the destination to cache messages for
     * @param connection  the database connection to use
     * @throws JMSException         for any JMS error
     * @throws PersistenceException if persistent messages can't be loaded from
     *                              the dataabase
     */
    public AbstractDestinationCache(JmsDestination destination,
                                    Connection connection)
            throws JMSException, PersistenceException {
        if (destination == null) {
            throw new IllegalArgumentException(
                    "Argument 'destination' is null");
        }
        if (!destination.getPersistent()) {
            throw new IllegalArgumentException(
                    "Argument 'destination' refers to a non-persistent destination");
        }
        _destination = destination;

        init(connection);

        MessageMgr.instance().addEventListener(getDestination(), this);
    }

    /**
     * Returns the destination that messages are being cached for.
     *
     * @return the destination that messages are being cached for
     */
    public JmsDestination getDestination() {
        return _destination;
    }

    /**
     * Register a consumer with this cache.
     *
     * @param consumer the message consumer for this destination
     * @return <code>true</code> if registered; otherwise <code>false</code>
     */
    public boolean addConsumer(ConsumerEndpoint consumer) {
        boolean result = false;

        // check to see that the consumer is actually one for this
        // destination
        if (consumer.getDestination().equals(getDestination())) {
            Long key = new Long(consumer.getId());
            if (!_consumers.containsKey(key)) {
                _consumers.put(key, consumer);
                result = true;
            }
        }

        return result;
    }

    /**
     * Remove the consumer for the list of registered consumers.
     *
     * @param consumer the consumer to remove
     */
    public void removeConsumer(ConsumerEndpoint consumer) {
        Long key = new Long(consumer.getId());
        _consumers.remove(key);
    }

    /**
     * Returns the number of messages in the cache.
     *
     * @return the number of messages in the cache
     */
    public int getMessageCount() {
        return _cache.getMessageCount();
    }

    /**
     * Determines if this cache can be destroyed. This implementation returns
     * <code>true</code> if there are no active consumers.
     *
     * @return <code>true</code> if the cache can be destroyed, otherwise
     *         <code>false</code>
     */
    public boolean canDestroy() {
        return !hasActiveConsumers();
    }

    /**
     * Destroy this cache
     */
    public synchronized void destroy() {
        // clear the cache
        _cache.clear();