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.http.core;

import static org.simpleframework.http.core.ContainerEvent.DISPATCH_FINISHED;
import static org.simpleframework.http.core.ContainerEvent.DISPATCH_REQUEST;
import static org.simpleframework.http.core.ContainerEvent.ERROR;

import org.simpleframework.http.Request;
import org.simpleframework.http.Response;
import org.simpleframework.http.message.Entity;
import org.simpleframework.transport.Channel;
import org.simpleframework.transport.trace.Trace;

/**
 * The <code>Dispatcher</code> object is used to dispatch a request and response
 * to the container. This is the root task that executes all transactions. A
 * transaction is dispatched to the container which can deal with it
 * asynchronously, however as a safeguard the dispatcher will catch any
 * throwables from the contains and close the connection if required. Closing
 * the connection if an exception is thrown ensures that CLOSE_WAIT issues do
 * not arise with open connections that can not be closed within the container.
 * 
 * @author Niall Gallagher
 * 
 * @see org.simpleframework.http.core.Container
 */
class Dispatcher implements Runnable {

    /**
     * This is the container that is used to handle the transactions.
     */
    private final Container container;

    /**
     * This is the response object used to response to the request.
     */
    private final Response response;

    /**
     * This is the request object which contains the request entity.
     */
    private final Request request;

    /**
     * This is the monitor object used to signal completion events.
     */
    private final Monitor monitor;

    /**
     * This is the channel associated with the request to dispatch.
     */
    private final Channel channel;

    /**
     * This is the trace that is used to track the request dispatch.
     */
    private final Trace trace;

    /**
     * Constructor for the <code>Dispatcher</code> object. This creates a
     * request and response object using the provided entity, these can then be
     * passed to the container to handle the transaction.
     * 
     * @param container
     *            this is the container to handle the request
     * @param reactor
     *            the reactor used to handle the next request
     * @param entity
     *            this contains the current request entity
     */
    public Dispatcher(Container container, Initiator reactor, Entity entity) {
        this.monitor = new FlushMonitor(reactor, entity);
        this.request = new RequestEntity(entity, this.monitor);
        this.response = new ResponseEntity(this.request, entity, this.monitor);
        this.channel = entity.getChannel();
        this.trace = this.channel.getTrace();
        this.container = container;
    }

    /**
     * This <code>run</code> method will dispatch the created request and
     * response objects to the container. This will interpret the target and
     * semantics from the request object and compose a response for the request
     * which is sent to the connected client.
     */
    @Override
    public void run() {
        try {
            this.dispatch();
        } catch (Exception cause) {
            this.trace.trace(ERROR, cause);
        } finally {
            this.trace.trace(DISPATCH_FINISHED);
        }
    }

    /**
     * This <code>dispatch</code> method will dispatch the request and response
     * objects to the container. This will interpret the target and semantics
     * from the request object and compose a response for the request which is
     * sent to the connected client. If there is an exception this will close
     * the socket channel.
     */
    private void dispatch() throws Exception {
        try {
            this.trace.trace(DISPATCH_REQUEST);
            this.container.handle(this.request, this.response);
        } catch (Throwable cause) {
            this.trace.trace(ERROR, cause);
            this.channel.close();
        }
    }
}