Dispatcher.java

/*
 * Dispatcher.java February 2007
 *
 * Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 
 * implied. See the License for the specific language governing 
 * permissions and limitations under the License.
 */

package org.simpleframework.transport;

import java.nio.channels.SocketChannel;

import org.simpleframework.transport.reactor.Operation;

/**
 * The <code>Dispatcher</code> operation is used transfer a transport to the
 * negotiator so it can be processed. This is uses so that when a pipeline is
 * given to the processor it can be dispatched in another thread to the
 * transporter. This is needed so that the connection thread is occupied only
 * briefly.
 * 
 * @author Niall Gallagher
 */
class Dispatcher implements Operation {

    /**
     * This is the negotiator used to transfer the transport to.
     */
    private final Negotiator negotiator;

    /**
     * This is the transport to be passed to the negotiator.
     */
    private final Transport transport;

    /**
     * Constructor for the <code>Dispatcher</code> object. This is used to
     * transfer a transport to a negotiator. Transferring the transport using an
     * operation ensures that the thread that is used to process the pipeline is
     * not occupied for long.
     * 
     * @param transport
     *            this is the transport this exchange uses
     * @param negotiator
     *            this is the negotiation to dispatch to
     */
    public Dispatcher(Transport transport, Negotiator negotiator) {
        this.negotiator = negotiator;
        this.transport = transport;
    }

    /**
     * This is the <code>SelectableChannel</code> which is used to determine if
     * the operation should be executed. If the channel is ready for a given I/O
     * event it can be run. For instance if the operation is used to perform
     * some form of read operation it can be executed when ready to read data
     * from the channel.
     * 
     * @return this returns the channel used to govern execution
     */
    @Override
    public SocketChannel getChannel() {
        return this.transport.getChannel();
    }

    /**
     * This is used to transfer the transport to the negotiator. This will
     * typically be executed asynchronously so that it does not delay the thread
     * that passes the <code>Pipeline</code> to the transport processor,
     * ensuring quicker processing.
     */
    @Override
    public void run() {
        try {
            this.negotiator.process(this.transport);
        } catch (Exception e) {
            this.cancel();
        }
    }

    /**
     * This is used to cancel the operation if it has timed out. This is
     * typically invoked when it has been waiting in a selector for an extended
     * duration of time without any active operations on it. In such a case the
     * reactor must purge the operation to free the memory and open channels
     * associated with the operation.
     */
    @Override
    public void cancel() {
        try {
            this.transport.close();
        } catch (Exception e) {
            return;
        }
    }
}