Netty5.0--相应式协议(ECHO)

EchoServer.java

/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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 com.netty.demo.echo;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

/**
 * Echoes back any received data from a client.
 */
public class EchoServer {

    private final int port;

    public EchoServer(int port) {
        this.port = port;
    }

    public void run() throws Exception {
        // Configure the server.
        EventLoopGroup bossGroup = new NioEventLoopGroup();//老板线程//bossGroup线程池用来接受客户端的连接请求
        EventLoopGroup workerGroup = new NioEventLoopGroup();//员工线程 //workerGroup线程池用来处理boss线程池里面的连接的数据
        try {
        	//通过ServerBootStrap对象，来启动服务器
            ServerBootstrap b = new ServerBootstrap();
            //通过group方法，来绑定EventLoopGroup，EventLoopGroup用来处理SocketChannel和Channel上面的所有时间和IO
            b.group(bossGroup, workerGroup);
            
            /*
             * 设置并绑定服务端Channel。作为NIO服务端，
             * 需要创建ServerSocketChannel,
             * Netty对原生的NIO类库进行了封装，
             * 对应实现是NioServerSocketChannel。
             * 对于用户而言，不需要关心服务端Channel的底层实现细节和工作原理，
             * 只需要指定具体使用哪种服务端Channel即可。
             * 因此，Netty的ServerBootstrap方法提供了channel方法用于指定服务端Channel的类型。
             * Netty通过工厂类，利用反射创建NioServerSocketChannel对象。
             * 由于服务端监听端口往往只需要在系统启动时才会调用，因此反射对性能的影响并不大
             */
            b.channel(NioServerSocketChannel.class);//设置并绑定服务端Channel,这里绑定NioServerSocketChannel
            
            AbstractBootstrap.option()用来设置ServerSocket的参数，AbstractBootstrap.childOption()用来设置Socket的参数。
            b.option(ChannelOption.SO_BACKLOG, 100);//?????
            
            b.handler(new LoggingHandler(LogLevel.INFO));
            
            //最后实例化一个ChannelInitializer
            /**
             * ChannelInitializer是一个特殊的handler，
             * 用来初始化ChannelPipeline里面的handler链。 
             * 这个特殊的ChannelInitializer在加入到pipeline后，
             * 在initChannel调用结束后,自身会被remove掉，从而完成初始化的效果
             */
            b.childHandler(new ChannelInitializer() {
                 @Override
                 public void initChannel(SocketChannel ch) throws Exception {
                     ch.pipeline().addLast(
                             //new LoggingHandler(LogLevel.INFO),
                             new EchoServerHandler());
                 }
             });

            // Start the server.
            ChannelFuture f = b.bind(port).sync();

            // Wait until the server socket is closed.
            f.channel().closeFuture().sync();
        } finally {
            // Shut down all event loops to terminate all threads.
        	//终结所有线程
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        int port=8088;
        if (args.length > 0) {
            port = Integer.parseInt(args[0]);
        } else {
            port = 8088;
        }
        System.out.println("启动服务");
        new EchoServer(8088).run();//执行echo
    }
}

EchoServerHandler.java

/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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 com.netty.demo.echo;

import io.netty.channel.ChannelHandler.Sharable;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Handler implementation for the echo server.
 */
@Sharable
public class EchoServerHandler extends ChannelHandlerAdapter {

    private static final Logger logger = Logger.getLogger(
            EchoServerHandler.class.getName());

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    	/**
    	 * Channel 公路，双向道，分为去路和来路。隐喻为网络连接。

			ChannelPipeline，公路管理部门，可以设置收费站，关卡等设施对车辆进行检查。
			
			ByteBuf 车辆。隐喻为网络连接中的数据。
			
			Handler 收费站，关卡；可以对公路上的车辆进行各种处理
    	 */
    	msg="wo qu ni ma";
    	System.out.println("------Handler 收费站，关卡；可以对公路上的车辆进行各种处理----------");
        ctx.write(msg);//把消息写入缓冲区
        ctx.flush();
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        //调用ctx.flush();方法把缓冲区的数据强行输出
    	ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // Close the connection when an exception is raised.
        logger.log(Level.WARNING, "Unexpected exception from downstream.", cause);
        ctx.close();
    }
}