rmijmsconnectionstub.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

/**
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 * ("Software"), with or without modification, are permitted provided
 * that the following conditions are met:
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 *    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
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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].
 *
 * 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 2000-2003 (C) Exoffice Technologies Inc. All Rights Reserved.
 *
 * $Id: RmiJmsConnectionStub.java,v 1.20 2003/08/07 13:32:54 tanderson Exp $
 *
 * Date         Author  Changes
 * 04/12/2000    jima    Created
 */
package org.exolab.jms.client.rmi;

import java.rmi.ConnectException;
import java.rmi.RemoteException;

import javax.jms.JMSException;

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

import org.exolab.jms.client.JmsConnectionStubIfc;
import org.exolab.jms.client.JmsErrorCodes;
import org.exolab.jms.client.JmsSessionStubIfc;
import org.exolab.jms.server.rmi.RemoteJmsServerConnectionIfc;
import org.exolab.jms.server.rmi.RemoteJmsServerSessionIfc;


/**
 * This class is repsonsible for returning a reference to a remote JMS
 * connection. If it cannot access get a remote connection then the constructor
 * will fail with a JMSException
 *
 * @version     $Revision: 1.20 $ $Date: 2003/08/07 13:32:54 $
 * @author      <a href="mailto:[e-mail]">Jim Alateras</a>
 */
public class RmiJmsConnectionStub
    implements JmsConnectionStubIfc {

    /**
     * This is a reference to the remote connection stub that is constructed
     * during object initialisation.
     */
    protected volatile RemoteJmsServerConnectionIfc _delegate = null;

    /**
     * This is a reference to the server stub that created this connection
     */
    protected RmiJmsServerStub _owner = null;

    /**
     * Cache a reference to the pinging thread. This thread is used to
     * determine whether the server is still active
     */
    private PingThread _pinger = null;

    /**
     * System property to override the max retries for failed rmi requests.
     * The default is 10
     */
    public final String MAX_RETRY_PROP = "org.exolab.jms.rmi.retryCount";

    /**
     * System property, which specifies the interval between successive
     * retries.
     * The value is specified in milliseconds and defaults to 100ms
     */
    public final String RETRY_INTERVAL_PROP =
        "org.exolab.jms.rmi.retryInterval";

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


    /**
     * Instantiate an instance of this class with the specified remote object.
     * This object is a delegate for all other requests. If a null connection
     * is specified then throw a JMSException exception
     *
     * @param       RemoteJmsServerConnectionIfc
     * @param       pingInterval            interval between client pings
     * @param       server                  the server creating the connection
     * @throws      JMSException
     */
    public RmiJmsConnectionStub(RemoteJmsServerConnectionIfc connection,
                                int pingInterval, RmiJmsServerStub server)
        throws JMSException {

        if (connection != null) {
            _owner = server;
            _delegate = connection;

            // this is used to determine whether or not the server is
            // active
            if (pingInterval > 0) {
                (_pinger = new PingThread(pingInterval)).start();
            }
        } else {
            throw new JMSException("Cannot instantiate with a null " +
                "connection");
        }
    }

    // implementation of JmsConnectionStubIfc.createSession
    public JmsSessionStubIfc createSession(int ackMode, boolean transacted)
        throws JMSException {
        RmiJmsSessionStub stub = null;
        try {
            RemoteJmsServerSessionIfc session = _delegate.createSession(
                ackMode, transacted);
            stub = new RmiJmsSessionStub(session);
            session.setMessageListener(stub);

        } catch (RemoteException exception) {
            // rethrow as a JMSException
            throw new JMSException("Failed to createSession  " + exception);
        }

        return stub;
    }

    // implementation of JmsConnectionStubIfc.close
    public void close() throws JMSException {
        // stop the pinging thread
        if (_pinger != null) {
            _pinger.close();
        }

        // close the delegate
        try {
            _delegate.close();
            _delegate = null;
        } catch (RemoteException exception) {
            // rethrow as a JMSException
            throw new JMSException("Failed to close  " + exception);
        }
    }

    // implementation of JmsConnectionStubIfc.getConnectionId
    public String getConnectionId() throws JMSException {
        try {
            return _delegate.getConnectionId();
        } catch (RemoteException exception) {
            // rethrow as a JMSException
            throw new JMSException("Failed to getConnectionId  " + exception);
        }
    }

    // implementation of JmsConnectionStubIfc.destroy
    public void destroy() {
        if (_pinger != null) {
            _pinger.close();
        }
        _delegate = null;
        _owner = null;
    }

    /**
     * This thread is used to send ping requests to the server. The server uses
     * these requests to determine whether a client has disconnected.
     * The frequency of these requests is determined by the server.
     */
    private class PingThread extends Thread {

        /**
         * Maintains the interval at which ping requests are generated to the
         * server. The value is in seconds
         */
        private int _interval;

        /**
         * The maximum no. of times to retry failed pings
         */
        private int _retries;

        /**
         * The interval between retrying failed pings
         */
        private int _retryInterval;

        /**
         * Determines if the thread should stop
         */
        private volatile boolean _stop = false;


        /**
         * Instantiate a daemon thread that will be used to periodically send
         * ping requests to the server at the specified interval
         *
         * @param interval the interval between ping requests in seconds
         */
        PingThread(int interval) {
            _interval = interval;
            setName("PingThread-" + Math.abs(hashCode()));
            setDaemon(true);

            _retries = getProperty(MAX_RETRY_PROP, 10, 1);
            _retryInterval = getProperty(RETRY_INTERVAL_PROP, 100, 100);
        }

        /**
         * This will run forever generating ping requests to the clients
         */
        public void run() {
            while (!_stop) {
                if (ping()) {
                    // sleep for the specified interval
                    try {
                        Thread.currentThread().sleep(_interval * 1000);
                    } catch (InterruptedException ignore) {
                    }
                } else {
                    // the server is no longer available so notify the
                    // client
                    try {
                        JMSException error = new JMSException(
                            "Connection to server terminated",
                            JmsErrorCodes.CONNECTION_TO_SERVER_DROPPED);
                        _log.warn("Server is not responding. "
                            + "Generating onException",
                            error);
                        _owner.getExceptionListener().onException(error);
                    } catch (Throwable ignore) {
                    }
                    break;
                }
            }
        }

        public void close() {
            _stop = true;
            try {
                interrupt();
            } catch (SecurityException ignore) {
            }
        }

        private boolean ping() {
            boolean successful = false;

            // send the ping request. We need to wrap this up in a
            // retry loop to cater for a ConnectException that happens
            // when the server is busy or out of resources.
            RemoteJmsServerConnectionIfc delegate = _delegate;
            if (delegate != null) {
                int count = 0;
                while ((count < _retries) && !successful && !_stop) {
                    try {
                        delegate.ping();
                        successful = true;
                    } catch (RemoteException exception) {
                        _log.warn("Failed to ping openjms server. "
                            + "Retry count=" + count, exception);
                        if ((exception.detail instanceof ConnectException) &&
                            (count < _retries - 1)) {
                            // underlying exception is connection
                            // related...let's retry the request after sleeping
                            try {
                                Thread.sleep(_retryInterval);
                            } catch (InterruptedException ignore) {
                            }
                        }
                    } catch (Throwable exception) {
                        // print the exception but continue
                        _log.warn("Exception pinging server", exception);
                    }
                    ++count;
                }
            }
            return successful;
        }

        private int getProperty(String name, int defaultValue, int minimum) {
            int result = defaultValue;
            String value = null;
            try {
                value = System.getProperty(name);
            } catch (SecurityException ignore) {
            }

            if (value != null) {
                try {
                    result = Integer.parseInt(value);
                    if (result <= minimum) {
                        result = minimum;
                    }
                } catch (NumberFormatException ignore) {
                    // keep the default
                }
            }
            return result;
        }

    } //-- PingThread

} //-- RmiJmsConnectionStub