managedconnectionhandle.java

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/**
 * 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 2004-2005 (C) Exoffice Technologies Inc. All Rights Reserved.
 *
 * $Id: ManagedConnectionHandle.java,v 1.5 2005/06/05 13:56:50 tanderson Exp $
 */
package org.exolab.jms.net.connector;

import org.exolab.jms.net.uri.URI;


/**
 * A handle to a {@link ManagedConnection} that tracks its utilisation.
 *
 * @author <a href="mailto:[e-mail]">Tim Anderson</a>
 * @version $Revision: 1.5 $ $Date: 2005/06/05 13:56:50 $
 */
final class ManagedConnectionHandle implements ManagedConnection {

    /**
     * The connection to delegate all requests to.
     */
    private final ManagedConnection _connection;

    /**
     * The connection factory for resolving connections via their URI.
     */
    private final ConnectionFactory _resolver;

    /**
     * The time the connection was last used, in milliseconds.
     */
    private long _lastUsed = 0;

    /**
     * The no. of active ConnectionHandle instances.
     */
    private volatile int _connectionCount = 0;


    /**
     * Construct a new <code>ManagedConnectionHandle</code>.
     *
     * @param connection the connection to delegate requests to
     * @param resolver   the connection factory for resolving connections via
     *                   their URI.
     */
    public ManagedConnectionHandle(ManagedConnection connection,
                                   ConnectionFactory resolver) {
        _connection = connection;
        _resolver = resolver;
    }

    /**
     * Registers a handler for handling invocations on objects exported via this
     * connection. Once a handler is registered, it cannot be de-registered.
     *
     * @param handler the invocation handler
     * @throws IllegalStateException if a handler is already registered
     * @throws ResourceException     for any error
     */
    public void setInvocationHandler(InvocationHandler handler)
            throws ResourceException {
        _connection.setInvocationHandler(handler);
    }

    /**
     * Registers a connection event listener.
     *
     * @param listener the connection event listener
     * @throws ResourceException for any error
     */
    public void setConnectionEventListener(ManagedConnectionListener listener)
            throws ResourceException {
        _connection.setConnectionEventListener(listener);
    }

    /**
     * Creates a new connection handle for the underlying physical connection.
     *
     * @return a new connection handle
     * @throws IllegalStateException if an <code>InvocationHandler</code> hasn't
     *                               been registered
     * @throws ResourceException     for any error
     */
    public Connection getConnection() throws ResourceException {
        Connection connection = _connection.getConnection();
        return new ConnectionHandle(connection);
    }

    /**
     * Determines if the underlying physical connection is alive.
     *
     * @return <code>true</code> if the connection is alive
     */
    public boolean isAlive() {
        return _connection.isAlive();
    }

    /**
     * Returns the remote address to which this is connected.
     *
     * @return the remote address to which this is connected
     * @throws ResourceException for any error
     */
    public URI getRemoteURI() throws ResourceException {
        return _connection.getRemoteURI();
    }

    /**
     * Returns the local address that this connection is bound to.
     *
     * @return the local address that this connection is bound to
     * @throws ResourceException for any error
     */
    public URI getLocalURI() throws ResourceException {
        return _connection.getLocalURI();
    }

    /**
     * Destroys the physical connection.
     *
     * @throws ResourceException for any error
     */
    public void destroy() throws ResourceException {
        _connection.destroy();
    }

    /**
     * Returns the last time the connection was used.
     * This is updated each time an invocation is performed,
     * via {@link #updateLastUsedTimestamp}.
     *
     * @return the last time the connction was used, in milliseconds, or
     *         <code>0</code> if the connection hasn't been used.
     */
    public synchronized long getLastUsedTimestamp() {
        return _lastUsed;
    }

    /**
     * Update the last used timestamp.
     */
    public synchronized void updateLastUsedTimestamp() {
        _lastUsed = System.currentTimeMillis();
    }

    /**
     * Determines if the connection can be destroyed. The connection
     * can be destroyed if there are no associated {@link Connection} instances.
     *
     * @return <code>true</code> if the connection may be destroyed
     */
    public boolean canDestroy() {
        return (_connectionCount == 0);
    }

    /**
     * Increment the no. of references to this connection.
     */
    private void incActiveConnections() {
        ++_connectionCount;
    }

    /**
     * Decrement the no. of references to this connection.
     */
    private void decActiveConnections() {
        --_connectionCount;
    }

    /**
     * Helper class to monitor a {@link Connection} instance, and invoke
     * <code>updateLastUsedTimestamp()</code> each time an invocation is
     * performed.
     */
    private class ConnectionHandle implements Connection {

        /**
         * The connection to delegate all requests to.
         */
        private final Connection _connection;

        /**
         * Construct a new <code>ConnectionHandle</code>.
         *
         * @param connection the connection to delegate requests to
         */
        public ConnectionHandle(Connection connection) {
            _connection = connection;
            incActiveConnections();
        }

        /**
         * Invoke a method on a remote object.
         *
         * @param request the request
         * @return the result of the invocation
         * @throws Throwable for any transport error
         */
        public Response invoke(Request request) throws Throwable {
            Response response = null;
            try {
                ConnectionContext.push(_resolver, this);
                response = _connection.invoke(request);
            } finally {
                updateLastUsedTimestamp();
                ConnectionContext.pop();
            }
            return response;
        }

        /**
         * Returns the remote address to which this is connected.
         *
         * @return the remote address to which this is connected
         * @throws ResourceException for any error
         */
        public URI getRemoteURI() throws ResourceException {
            return _connection.getRemoteURI();
        }

        /**
         * Returns the local address that this connection is bound to.
         *
         * @return the local address that this connection is bound to
         * @throws ResourceException for any error
         */
        public URI getLocalURI() throws ResourceException {
            return _connection.getLocalURI();
        }

        /**
         * Called by the garbage collector when there are no more references to
         * the object.
         */
        protected void finalize() {
            decActiveConnections();
        }
    }
}