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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2009 Red Hat, Inc.
 *
 * Red Hat licenses this file to you 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.jboss.netty.channel;

import java.net.SocketAddress;


/**
 * A {@link ChannelDownstreamHandler} which provides an individual handler
 * method for each event type.  This handler down-casts the received downstream
 * event into more meaningful sub-type event and calls an appropriate handler
 * method with the down-cast event.  The names of the methods starts with the
 * name of the operation and ends with {@code "Requested"}
 * (e.g. {@link #writeRequested(ChannelHandlerContext, MessageEvent) writeRequested}.)
 * 
 * Please use {@link SimpleChannelHandler} if you need to implement both
 * {@link ChannelUpstreamHandler} and {@link ChannelDownstreamHandler}.
 *
 * 
Overriding the {@link #handleDownstream(ChannelHandlerContext, ChannelEvent) handleDownstream} method
 * 
 * You can override the {@link #handleDownstream(ChannelHandlerContext, ChannelEvent) handleDownstream}
 * method just like overriding an ordinary Java method.  Please make sure to
 * call {@code super.handleDownstream()} so that other handler methods are
 * invoked properly:
 * 
 * public class MyChannelHandler extends {@link SimpleChannelDownstreamHandler} {
 *
 *     {@code @Override}
 *     public void handleDownstream({@link ChannelHandlerContext} ctx, {@link ChannelEvent} e) throws Exception {
 *
 *         // Log all channel state changes.
 *         if (e instanceof {@link MessageEvent}) {
 *             logger.info("Writing:: " + e);
 *         }
 *
 *         super.handleDownstream(ctx, e);
 *     }
 * }
 *
 * @author The Netty Project
 * @author Trustin Lee
 *
 * @version $Rev: 2122 $, $Date: 2010-02-02 11:00:04 +0900 (Tue, 02 Feb 2010) $
 */
public class SimpleChannelDownstreamHandler implements ChannelDownstreamHandler {

    /**
     * Creates a new instance.
     */
    public SimpleChannelDownstreamHandler() {
        super();
    }

    /**
     * {@inheritDoc}  Down-casts the received downstream event into more
     * meaningful sub-type event and calls an appropriate handler method with
     * the down-casted event.
     */
    public void handleDownstream(ChannelHandlerContext ctx, ChannelEvent e)
            throws Exception {

        if (e instanceof MessageEvent) {
            writeRequested(ctx, (MessageEvent) e);
        } else if (e instanceof ChannelStateEvent) {
            ChannelStateEvent evt = (ChannelStateEvent) e;
            switch (evt.getState()) {
            case OPEN:
                if (!Boolean.TRUE.equals(evt.getValue())) {
                    closeRequested(ctx, evt);
                }
                break;
            case BOUND:
                if (evt.getValue() != null) {
                    bindRequested(ctx, evt);
                } else {
                    unbindRequested(ctx, evt);
                }
                break;
            case CONNECTED:
                if (evt.getValue() != null) {
                    connectRequested(ctx, evt);
                } else {
                    disconnectRequested(ctx, evt);
                }
                break;
            case INTEREST_OPS:
                setInterestOpsRequested(ctx, evt);
                break;
            default:
                ctx.sendDownstream(e);
            }
        } else {
            ctx.sendDownstream(e);
        }
    }

    /**
     * Invoked when {@link Channel#write(Object)} is called.
     */
    public void writeRequested(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
        ctx.sendDownstream(e);
    }

    /**
     * Invoked when {@link Channel#bind(SocketAddress)} was called.
     */
    public void bindRequested(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        ctx.sendDownstream(e);

    }

    /**
     * Invoked when {@link Channel#connect(SocketAddress)} was called.
     */
    public void connectRequested(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        ctx.sendDownstream(e);

    }

    /**
     * Invoked when {@link Channel#setInterestOps(int)} was called.
     */
    public void setInterestOpsRequested(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        ctx.sendDownstream(e);
    }

    /**
     * Invoked when {@link Channel#disconnect()} was called.
     */
    public void disconnectRequested(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        ctx.sendDownstream(e);

    }

    /**
     * Invoked when {@link Channel#unbind()} was called.
     */
    public void unbindRequested(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        ctx.sendDownstream(e);

    }

    /**
     * Invoked when {@link Channel#close()} was called.
     */
    public void closeRequested(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        ctx.sendDownstream(e);
    }
}