Netty 学习1.Hello World

案例说明：客户端发送一个信息到服务器端，服务器端将信息原样返回

0 添加maven依赖

        
            junit
            junit
            3.8.1
            test
        
        
        
            io.netty
            netty-all
            4.0.21.Final
        

1. ServerHandler

《Netty in Action》中介绍过，我们不需要使每一个inboundChannel继承于ChannelInboundHandler，这样会需要我们实现ChannelInboundHandler中的所有接口，在一般的channel中我们没有必要这样做，这样只会增加我们的额外的工作量，我们只需要继承ChannelInboundHandlerAdapter，继承它的适配就可以了，我们需要实现几个特别重要的方法，例如读取的方法channelRead和异常处理的方法exceptionCaught，源码如下：

package com.ly.netty.hello;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class HelloWorldServerHandler extends ChannelInboundHandlerAdapter{
    
    
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("Hello");
        super.channelActive(ctx);
    }
    
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println("server channelRead..");
        System.out.println(ctx.channel().remoteAddress()+ msg.toString());
        ctx.flush();
    }
    
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }

}

2. Server

接下来我们就要写Netty的服务器端了。写server端需要注意，就是需要关闭连接，释放线程资源，源码如下：

package com.ly.netty.hello;

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.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;


public class HelloWorldServer {

    private int port;
    
    public HelloWorldServer(int port) {
        this.port = port;
    }
    
    public void start(){
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap sbs = new ServerBootstrap();
            sbs.group(bossGroup,workerGroup);
            sbs.channel(NioServerSocketChannel.class);
            sbs.childHandler(new ChannelInitializer() {
                        
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast("decoder", new StringDecoder());
                            ch.pipeline().addLast("encoder", new StringEncoder());
                            ch.pipeline().addLast(new HelloWorldServerHandler());
                        };
                        
                    }).option(ChannelOption.SO_BACKLOG, 128)   
                    .childOption(ChannelOption.SO_KEEPALIVE, true);
             // 绑定端口，开始接收进来的连接
             ChannelFuture future = sbs.bind(port).sync();  
             
             System.out.println("Server start listen at " + port );
             future.channel().closeFuture().sync();
        } catch (Exception e) {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
    
    public static void main(String[] args) throws Exception {
        int port;
        if (args.length > 0) {
            port = Integer.parseInt(args[0]);
        } else {
            port = 8080;
        }
        new HelloWorldServer(port).start();
    }
}

3. ClientHandler

如法炮制，客户端的handler，我们依旧命名为HelloWorldClientHandler，也是继承于ChannelInboundHandlerAdapter。

package com.ly.netty.hello;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class HelloWorldClientHandler extends ChannelInboundHandlerAdapter{
    
    
      @Override
      public void channelActive(ChannelHandlerContext ctx) {
          System.out.println("HelloWorldClientHandler Active");
          ctx.fireChannelActive();
      }
  
      @Override
      public void channelRead(ChannelHandlerContext ctx, Object msg) {
         System.out.println("HelloWorldClientHandler read Message:"+msg);
      }
      
      @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
          System.out.println("HelloWorldClientHandler inActive!");
        super.channelInactive(ctx);
    }
  
  
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
         cause.printStackTrace();
         ctx.close();
      }

}

4. Client

完整的代码如下：

package com.ly.netty.hello;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.net.InetSocketAddress;
import java.net.SocketAddress;

public class HelloWorldClient {
    
    static final String HOST = System.getProperty("host", "127.0.0.1");
    static final int PORT = Integer.parseInt(System.getProperty("port", "8080"));
    static final int SIZE = Integer.parseInt(System.getProperty("size", "256"));

    public static void main(String[] args) throws Exception {
        initChannel();
    }
    
    public static void initChannel() throws InterruptedException{
        // Configure the client.
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
             .channel(NioSocketChannel.class)
             .option(ChannelOption.TCP_NODELAY, true)
             .handler(new ChannelInitializer() {
                 @Override
                 public void initChannel(SocketChannel ch) throws Exception {
                     ChannelPipeline p = ch.pipeline();
                     p.addLast("decoder", new StringDecoder());
                     p.addLast("encoder", new StringEncoder());
                     p.addLast(new HelloWorldClientHandler());
                 }
             });
//            SocketAddress socketAddress = InetSocketAddress.createUnresolved(address.getHost(), address.getPort());
            SocketAddress socketAddress =  new InetSocketAddress(HOST, PORT);
            ChannelFuture future = b.connect(socketAddress).sync();
            future.channel().writeAndFlush("hello world");
            future.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    
    }

}

Netty的服务器端和客户端就搭建完。我们做到了客户端发送信息，服务器端接收且把收到的信息原样返回给客户端了。

我的Github项目，欢迎大家指导！Watch！Star！Fork! Thanks！
GitHub-Netty-demo-server
GitHub-Netty-demo-client