multiplexer.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

/**
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 *    please contact [e-mail].
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 * 5. Due credit should be given to the Exolab Project
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 *
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 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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 *
 * Copyright 2003-2005 (C) Exoffice Technologies Inc. All Rights Reserved.
 *
 * $Id: Multiplexer.java,v 1.9 2006/12/16 12:37:17 tanderson Exp $
 */
package org.exolab.jms.net.multiplexer;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.exolab.jms.common.security.BasicPrincipal;
import org.exolab.jms.net.connector.Authenticator;
import org.exolab.jms.net.connector.ResourceException;
import org.exolab.jms.net.connector.SecurityException;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ProtocolException;
import java.security.Principal;
import java.util.HashMap;
import java.util.LinkedList;


/**
 * This class multiplexes data over a physical connection.
 *
 * @author <a href="mailto:[e-mail]">Tim Anderson</a>
 * @version $Revision: 1.9 $ $Date: 2006/12/16 12:37:17 $
 */
public class Multiplexer implements Constants, Runnable {

    /**
     * The listener to notify.
     */
    private MultiplexerListener _listener;

    /**
     * If <code>true</code>, indicates that the multiplexer has been closed.
     */
    private volatile boolean _closed;

    /**
     * The endpoint.
     */
    private Endpoint _endpoint;

    /**
     * The endpoint's output stream.
     */
    private DataOutputStream _out;

    /**
     * The endpoint's input stream.
     */
    private DataInputStream _in;

    /**
     * The set of channels managed by this, keyed on channel identifier.
     */
    private final HashMap _channels = new HashMap();

    /**
     * The set of free channels, keyed on channel identifier.
     */
    private final LinkedList _free = new LinkedList();

    /**
     * If <code>true</code>, indicates that the physical connection was opened
     * (client), rather than accepted (server). This is used in channel
     * identifier generation
     */
    private boolean _client = false;

    /**
     * The channel identifier seed.
     */
    private int _seed = 0;

    /**
     * The principal that owns the connection, or <code>null</code>,
     * if this is an unauthenticated connection.
     */
    private Principal _principal;

    /**
     * The sending and receiving buffer size, in bytes.
     */
    private static final int BUFFER_SIZE = 2048;

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

    /**
     * Construct a new client-side <code>Multiplexer</code>.
     *
     * @param listener  the multiplexer listener
     * @param endpoint  the endpoint to multiplex messages over
     * @param principal the security principal
     * @throws IOException       if an I/O error occurs
     * @throws SecurityException if connection is refused by the server
     */
    public Multiplexer(MultiplexerListener listener, Endpoint endpoint,
                       Principal principal)
            throws IOException, SecurityException {
        initialise(listener, endpoint, true);
        authenticate(principal);
    }

    /**
     * Construct a new server-side <code>Multiplexer</code>.
     *
     * @param listener      the multiplexer listener
     * @param endpoint      the endpoint to multiplex messages over
     * @param authenticator the connection authenticator
     * @throws IOException       if an I/O error occurs
     * @throws ResourceException if the authenticator cannot authenticate
     */
    public Multiplexer(MultiplexerListener listener, Endpoint endpoint,
                       Authenticator authenticator)
            throws IOException, ResourceException {
        initialise(listener, endpoint, false);
        authenticate(authenticator);
    }

    /**
     * Construct a new <code>Multiplexer</code>.
     * <p/>
     * This constructor is provided for subclasses that must perform setup
     * work prior to invoking {@link #initialise}
     */
    protected Multiplexer() {
    }

    /**
     * Start multiplexing.
     */
    public void run() {
        while (!_closed) {
            multiplex();
        }
    }

    /**
     * Returns a free channel from the pool, opening a new one if none are
     * available.
     *
     * @return a free channel
     * @throws IOException if an I/O error occurs
     */
    public Channel getChannel() throws IOException {
        Channel channel = null;

        synchronized (_free) {
            if (!_free.isEmpty()) {
                channel = (Channel) _free.removeFirst();
            }
        }

        if (channel == null) {
            channel = open();
        }

        return channel;
    }

    /**
     * Releases a channel back to the pool.
     *
     * @param channel the channel to release
     */
    public void release(Channel channel) {
        synchronized (_free) {
            _free.add(channel);
        }
    }

    /**
     * Close a channel.
     *
     * @param channel the channel to close
     * @throws IOException if an I/O error occurs
     */
    public void close(Channel channel) throws IOException {
        int channelId = channel.getId();
        synchronized (_channels) {
            _channels.remove(new Integer(channelId));
        }

        send(CLOSE, channelId);
    }

    /**
     * Send a message.
     *
     * @param type the packet type
     * @throws IOException if an I/O error occurs
     */
    public void send(byte type) throws IOException {
        synchronized (_out) {
            _out.writeByte(type);
            _out.flush();
            if (_log.isDebugEnabled()) {
                _log.debug("send(type=0x" + Integer.toHexString(type) + ")");
            }
        }
    }

    /**
     * Send a message.
     *
     * @param type      the packet type
     * @param channelId the identifier of the channel sending the message
     * @throws IOException if an I/O error occurs
     */
    public void send(byte type, int channelId) throws IOException {
        synchronized (_out) {
            _out.writeByte(type);
            _out.writeShort(channelId);
            _out.flush();
            if (_log.isDebugEnabled()) {
                _log.debug("send(type=0x" + Integer.toHexString(type)
                        + ", channel=" + channelId + ")");
            }
        }
    }

    /**
     * Send a message.
     *
     * @param type      the packet type
     * @param channelId the identifier of the channel sending the message
     * @param data      the data to send
     * @throws IOException if an I/O error occurs
     */
    public void send(byte type, int channelId, int data) throws IOException {
        synchronized (_out) {
            _out.writeByte(type);
            _out.writeShort(channelId);
            _out.writeInt(data);
            _out.flush();
            if (_log.isDebugEnabled()) {
                _log.debug("send(type=" + type + ", channel=" + channelId
                        + ", data=" + Integer.toHexString(data) + ")");
            }
        }
    }

    /**
     * Send a message.
     *
     * @param type      the packet type
     * @param channelId the identifier of the channel sending the message
     * @param data      the data to send
     * @param offset    the offset into the data
     * @param length    the length of data
     * @throws IOException if an I/O error occurs
     */
    public void send(byte type, int channelId, byte[] data, int offset,
                     int length) throws IOException {
        synchronized (_out) {
            _out.writeByte(type);
            _out.writeShort(channelId);
            _out.writeInt(length);
            _out.write(data, offset, length);
            _out.flush();
        }
    }

    /**
     * Ping the connection.
     *
     * @param token the token to be returned in the reply
     * @throws IOException if an I/O error occurs
     */
    public void ping(int token) throws IOException {
        synchronized (_out) {
            _out.writeByte(PING_REQUEST);
            _out.writeInt(token);
            _out.flush();
            if (_log.isDebugEnabled()) {
                _log.debug("ping(token=" + token + ")");
            }
        }
    }

    /**
     * Close the multiplexer, releasing any resources. This closes the socket
     * and waits for the thread to terminate.
     */
    public void close() {
        if (!_closed) {
            _closed = true;
            try {
                send(SHUTDOWN);
            } catch (IOException exception) {
                _log.debug(exception);
            }
            try {
                _endpoint.close();
            } catch (IOException exception) {
                _log.debug(exception);
            }
            // _pool.shutdownAfterProcessingCurrentlyQueuedTasks();
            // @todo - as the pool is shared, need to block for
            // tasks queued by this
        }
    }

    /**
     * Determines if the multiplexer is closed.
     *
     * @return <code>true</code> if the multiplexer is closed
     */
    public boolean isClosed() {
        return _closed;
    }

    /**
     * Determines if this is a client-side instance.
     *
     * @return <code>true</code> if this is a client-side instance,
     *         <code>false</code> if it is a server=side instance
     */
    public boolean isClient() {
        return _client;
    }

    /**
     * Returns the principal that owns the connection.
     *
     * @return the principal that owns the connection, or <code>null<code>
     *         if this is an unauthenticated connection
     */
    public Principal getPrincipal() {
        return _principal;
    }

    /**
     * Initialise the multiplexer.
     *
     * @param listener the multiplexer listener
     * @param endpoint the endpoint to multiplex messages over
     * @param client   determines if this is a client-side or server-side
     *                 instance
     * @throws IOException if an I/O error occurs
     */
    protected void initialise(MultiplexerListener listener, Endpoint endpoint,
                              boolean client)
            throws IOException {


        if (listener == null) {
            throw new IllegalArgumentException("Argument 'listener' is null");
        }
        if (endpoint == null) {
            throw new IllegalArgumentException("Argument 'endpoint' is null");
        }
        if (_log.isDebugEnabled()) {
            _log.debug("Multiplexer(uri=" + endpoint.getURI()
                    + ", client=" + client);
        }
        _listener = listener;
        _endpoint = endpoint;
        _out = new DataOutputStream(endpoint.getOutputStream());
        _in = new DataInputStream(endpoint.getInputStream());
        _client = client;