Netty 快速入门系列 - Chapter 2 Netty3.x 【第三讲】Hello

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Chapter2 章节结构

1. Netty版本大致版本分为 netty3.x 和 netty4.x、netty5.x

2. 应用范围

1. 分布式进程通信
例如: hadoop、dubbo、akka等具有分布式功能的框架，底层RPC通信都是基于netty实现的，这些框架使用的版本通常都还在用netty3.x

2. 游戏服务器开发

最新的游戏服务器有部分公司可能已经开始采用netty4.x 或 netty5.x

3. Hello World案例

Server端

a. HelloServer

package com.john.netty.learn.ch02_03.server;


import java.net.InetSocketAddress;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;


import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelEvent;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelHandler;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.ChannelSink;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;


public class HelloServer {


  public HelloServer(int port) {


     ServerBootstrap serverBootstrap = new ServerBootstrap();


     serverBootstrap.setFactory(new NioServerSocketChannelFactory(boss, workers));


     serverBootstrap.setPipelineFactory(new ChannelPipelineFactory() {


       @Override
       public ChannelPipeline getPipeline() throws Exception {


          ChannelPipeline channelPipeline = Channels.pipeline();
          channelPipeline.addLast("Decoder", new StringDecoder());
          channelPipeline.addLast("HelloWorldHandler", new HelloChannelHandler());
          channelPipeline.addLast("Encoder", new StringEncoder());


          return channelPipeline;
       }
     });


     serverBootstrap.bind(new InetSocketAddress(port));
  }


  private ExecutorService boss = Executors.newCachedThreadPool();


  private ExecutorService workers = Executors.newCachedThreadPool();


  public static void main(String[] args) {


     new HelloServer(3000);
  }
}

b. HelloChannelHandler

package com.john.netty.learn.ch02_03.server;


import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;


public class HelloChannelHandler extends SimpleChannelHandler {


  public HelloChannelHandler() {


  }


  /**
   * 接收到消息
   */
  @Override
  public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {


     // 没有过滤器
     // ChannelBuffer channelBuffer = (ChannelBuffer) e.getMessage();
     // System.out.println("接收到消息：" + new String(channelBuffer.array()));


     // 回写数据
     // ctx.getChannel().write(ChannelBuffers.wrappedBuffer(("Hi " +
     // e.getMessage()).getBytes()));


     // channelPipeline.addLast("Decoder", new StringDecoder());
     System.out.println("接收到消息：" + e.getMessage());


     // channelPipeline.addLast("Encoder", new StringEncoder());
     ctx.getChannel().write("Hi " + e.getMessage());


  }


  @Override
  public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
     System.out.println("channelConnected");
     super.channelConnected(ctx, e);
  }


  /**
   * 建立Channel成功，关闭通道时候，才会触发Disconnect
   */
  @Override
  public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {


     System.out.println("channelDisconnected");


     super.channelDisconnected(ctx, e);
  }


  /**
   * Channel 关闭
   */
  @Override
  public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {


     System.out.println("channelClosed");


     super.channelClosed(ctx, e);
  }


  /**
   * 捕获异常
   */


  @Override
  public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
     e.getCause().printStackTrace();
     super.exceptionCaught(ctx, e);
  }
}

Client端

a. HelloClient

package com.john.netty.learn.ch02_03.client;


import java.net.InetSocketAddress;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;


import org.jboss.netty.bootstrap.ClientBootstrap;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFactory;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;


import com.john.netty.learn.ch02_03.server.HelloChannelHandler;


public class HelloClient {


  public HelloClient(String ip, int port) {


    ClientBootstrap clientBootstrap = new ClientBootstrap();


    clientBootstrap.setFactory(new NioClientSocketChannelFactory(boss, workers));


    clientBootstrap.setPipelineFactory(new ChannelPipelineFactory() {


      @Override
      public ChannelPipeline getPipeline() throws Exception {


        ChannelPipeline channelPipeline = Channels.pipeline();
        channelPipeline.addLast("Decoder", new StringDecoder());
        channelPipeline.addLast("HiHandler", new HiChannelHandler());
        channelPipeline.addLast("Encoder", new StringEncoder());


        return channelPipeline;
      }
    });


    ChannelFuture channelFuture = clientBootstrap.connect(new InetSocketAddress(ip, port));


    Channel channel = channelFuture.getChannel();


    System.out.println("client start");


    Scanner scanner = new Scanner(System.in);


    while (true) {


      System.out.println("Please input:");
      channel.write(scanner.nextLine());


    }


  }


  private ExecutorService boss = Executors.newSingleThreadExecutor();


  private ExecutorService workers = Executors.newCachedThreadPool();


  public static void main(String[] args) {


    new HelloClient("127.0.0.1", 3000);
  }


}

b. HiChannelHandler

package com.john.netty.learn.ch02_03.client;


import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;


public class HiChannelHandler extends SimpleChannelHandler {


  public HiChannelHandler() {


  }


  /**
   * 接收到消息
   */
  @Override
  public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {


     // 没有过滤器
     // ChannelBuffer channelBuffer = (ChannelBuffer) e.getMessage();
     // System.out.println("接收到消息：" + new String(channelBuffer.array()));


     // 回写数据
     // ctx.getChannel().write(ChannelBuffers.wrappedBuffer(("Hi " +
     // e.getMessage()).getBytes()));


     // channelPipeline.addLast("Decoder", new StringDecoder());
     System.out.println("接收到消息：" + e.getMessage());


     


  }


  @Override
  public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
     System.out.println("channelConnected");
     super.channelConnected(ctx, e);
  }


  /**
   * 建立Channel成功，关闭通道时候，才会触发Disconnect
   */
  @Override
  public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {


     System.out.println("channelDisconnected");


     super.channelDisconnected(ctx, e);
  }


  /**
   * Channel 关闭
   */
  @Override
  public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {


     System.out.println("channelClosed");


     super.channelClosed(ctx, e);
  }


  /**
   * 捕获异常
   */


  @Override
  public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
     e.getCause().printStackTrace();
     super.exceptionCaught(ctx, e);
  }
}

Netty hello world 讲解说明：

1、netty服务端hello world案例

SimpleChannelHandler 处理消息接收和写
messageReceived接收消息
channelConnected新连接，通常用来检测IP是否是黑名单
hannelDisconnected链接关闭，可以再用户断线的时候清楚用户的缓存数据等

2、netty客户端hello world案例

channelDisconnected与channelClosed的区别？
channelDisconnected只有在连接建立后断开才会调用
channelClosed无论连接是否成功都会调用关闭资源