destinations.java

OpenJMS是一个开源的Java Message Service API 1.0.2 规范的实现,它包含有以下特性： *. 它既支持点到点（point-to-point）（PTP）模型和发布/订

/**
 * Redistribution and use of this software and associated documentation
 * ("Software"), with or without modification, are permitted provided
 * 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 2000-2005 (C) Exoffice Technologies Inc. All Rights Reserved.
 */
package org.exolab.jms.persistence;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Vector;

import org.exolab.jms.client.JmsDestination;
import org.exolab.jms.client.JmsQueue;
import org.exolab.jms.client.JmsTopic;


/**
 * This class provides persistency for JmsDestination objects in an RDBMS
 * database.
 *
 * @author <a href="mailto:[e-mail]">Tim Anderson</a>
 * @version $Revision: 1.4 $ $Date: 2005/08/31 05:45:50 $
 */
class Destinations {

    /**
     * The seed generator.
     */
    private final SeedGenerator _seeds;

    /**
     * The consumer manager.
     */
    private final Consumers _consumers;

    /**
     * Cache of all destinations indexed on names.
     */
    private final HashMap _destinations = new HashMap();

    /**
     * Cache of all destinations indexed on identity.
     */
    private final HashMap _ids = new HashMap();

    /**
     * This is the name of the destination id generator, which uniquely created
     * identities for destinations.
     */
    private static final String DESTINATION_ID_SEED = "destinationId";

    /**
     * Create a new <code>Destinations</code>.
     *
     * @param seeds the seed manager
     * @param consumers the consumer manager
     * @param connection the connection to initialise from
     * @throws PersistenceException if initialisation fails
     */
    public Destinations(SeedGenerator seeds,
                        Consumers consumers,
                        Connection connection) throws PersistenceException {
        _seeds = seeds;
        _consumers = consumers;
        load(connection);
    }

    /**
     * Add a new destination to the database. This method will also assign it a
     * unique identity.
     *
     * @param connection  the connection to use.
     * @param destination the destination to add
     * @throws PersistenceException if the destination cannot be added
     */
    public synchronized void add(Connection connection,
                                 JmsDestination destination)
            throws PersistenceException {

        PreparedStatement insert = null;
        try {
            long Id = _seeds.next(connection, DESTINATION_ID_SEED);
            boolean isQueue = (destination instanceof JmsQueue);

            insert = connection.prepareStatement(
                    "insert into destinations (name, isqueue, destinationid) "
                    + "values (?, ?, ?)");
            insert.setString(1, destination.getName());
            insert.setBoolean(2, isQueue);
            insert.setLong(3, Id);
            insert.executeUpdate();
            cache(destination, Id);
        } catch (Exception error) {
            throw new PersistenceException("Destinations.add failed with " +
                                           error.toString());
        } finally {
            SQLHelper.close(insert);
        }
    }

    /**
     * Remove a destination from the database. This removes all associated
     * consumers, and messages.
     *
     * @param connection  the connection to use
     * @param destination the destination
     * @return <code>true</cpde> if it was removed
     * @throws PersistenceException if the request fails
     */
    public synchronized boolean remove(Connection connection,
                                       JmsDestination destination)
            throws PersistenceException {

        boolean success = false;
        PreparedStatement deleteDestinations = null;
        PreparedStatement deleteMessages = null;
        PreparedStatement deleteConsumers = null;
        PreparedStatement deleteMessageHandles = null;

        Pair pair = (Pair) _destinations.get(destination.getName());
        if (pair != null) {
            try {
                deleteDestinations = connection.prepareStatement(
                        "delete from destinations where name=?");
                deleteDestinations.setString(1, destination.getName());

                deleteMessages = connection.prepareStatement(
                        "delete from messages where destinationId=?");
                deleteMessages.setLong(1, pair.Id);

                deleteMessageHandles = connection.prepareStatement(
                        "delete from message_handles where destinationId=?");
                deleteMessageHandles.setLong(1, pair.Id);

                deleteConsumers = connection.prepareStatement(
                        "delete from consumers where destinationId=?");
                deleteConsumers.setLong(1, pair.Id);


                deleteDestinations.executeUpdate();
                deleteMessages.executeUpdate();
                deleteMessageHandles.executeUpdate();
                deleteConsumers.executeUpdate();

                _consumers.removeCached(pair.Id);
                _destinations.remove(destination.getName());
                _ids.remove(new Long(pair.Id));
                success = true;
            } catch (Exception error) {
                throw new PersistenceException("Failed to remove destination",
                                               error);
            } finally {
                SQLHelper.close(deleteDestinations);
                SQLHelper.close(deleteMessages);
                SQLHelper.close(deleteConsumers);
                SQLHelper.close(deleteMessageHandles);
            }
        }

        return success;
    }

    /**
     * Returns the destination associated with name.
     *
     * @param name the name of the destination
     * @return the destination, or null
     */
    public synchronized JmsDestination get(String name) {
        Pair pair = (Pair) _destinations.get(name);
        return (pair != null) ? pair.destination : null;
    }

    /**
     * Returns the destination associated with Id.
     *
     * @param id the destination Id
     * @return the destination or null
     */
    public synchronized JmsDestination get(long id) {
        Pair pair = (Pair) _ids.get(new Long(id));
        return (pair != null) ? pair.destination : null;
    }

    /**
     * Returns the Id for a given destination name
     *
     * @param name the destination name
     * @return the destination Id, or 0 if it doesn't exist
     */
    public synchronized long getId(String name) {
        Pair pair = (Pair) _destinations.get(name);
        return (pair != null) ? pair.Id : 0;
    }

    /**
     * Returns the list of destination names.
     *
     * @return list of destination names
     */
    public synchronized Vector getNames() {
        // return a Vector for legacy reasons.
        Vector result = new Vector(_destinations.size());
        Iterator iter = _destinations.keySet().iterator();
        while (iter.hasNext()) {
            result.add((String) iter.next());
        }

        return result;
    }

    /**
     * Returns the list of destination objects.
     *
     * @return list of destination objects
     */
    public synchronized Vector getDestinations() {
        // return a Vector for legacy reasons.
        Vector result = new Vector(_destinations.size());
        Iterator iter = _destinations.values().iterator();
        while (iter.hasNext()) {
            result.add(((Pair) iter.next()).destination);
        }

        return result;
    }

    /**
     * Deallocates resources owned or referenced by the instance.
     */
    public synchronized void close() {
        _destinations.clear();
        _ids.clear();
    }

    /**
     * Load all the destinations in memory. It uses the transaction service and
     * the database service to access the appropriate resources.
     *
     * @param connection the connection to use
     * @throws PersistenceException if the
     */
    private void load(Connection connection)
            throws PersistenceException {

        PreparedStatement select = null;
        ResultSet set = null;
        try {
            select = connection.prepareStatement(
                    "select name, isqueue, destinationid from destinations");

            set = select.executeQuery();
            String name = null;
            boolean isQueue = false;
            JmsDestination destination = null;
            long Id = 0;
            while (set.next()) {
                name = set.getString(1);
                isQueue = set.getBoolean(2);
                destination = (isQueue)
                        ? (JmsDestination) new JmsQueue(name)
                        : (JmsDestination) new JmsTopic(name);
                Id = set.getLong(3);
                destination.setPersistent(true);
                cache(destination, Id);
            }
        } catch (Exception exception) {
            throw new PersistenceException("Failed to load destinations",
                                           exception);
        } finally {
            SQLHelper.close(set);
            SQLHelper.close(select);
        }
    }

    /**
     * Cache a destination.
     *
     * @param destination the destination to cache
     * @param Id          the destination identity
     */
    private void cache(JmsDestination destination, long Id) {
        Pair pair = new Pair(destination, Id);

        _destinations.put(destination.getName(), pair);
        _ids.put(new Long(Id), pair);
    }


    /**
     * This private static class holds the name and identity of the destination
     */
    private static class Pair {

        public Pair(JmsDestination destination, long Id) {
            this.destination = destination;
            this.Id = Id;
        }

        public JmsDestination destination;
        public long Id;
    }
}