Netty 入门

　　Netty是一个nio的框架。但是对于新学习的同学来说，netty有点不太好入手。这里写个小demo，实现一个比较简单的netty的服务端和客户端。

　　Netty 大概有几个模块：

　　服务端：

　　1.服务端的接入类。用于创建和接收相应的传入信息。2.handler 用于对请求进行实际处理。

　　客户端：

　　1.客户端接入，用于创建接入连接。 2.handler 用于接收服务端的返回内容。

　　代码如下：　　

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;

public class Server {

    public static void main(String[] args) throws Exception {
        //1 第一个线程组 是用于接收Client端连接的
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        //2 第二个线程组 是用于实际的业务处理操作的
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        
        //3 创建一个辅助类Bootstrap，就是对我们的Server进行一系列的配置

        ServerBootstrap b = new ServerBootstrap();
        //把俩个工作线程组加入进来
        b.group(bossGroup, workerGroup)
        //我要指定使用NioServerSocketChannel这种类型的通道
         .channel(NioServerSocketChannel.class)
        //一定要使用 childHandler 去绑定具体的 事件处理器
         .childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(new ServerHandler());
            }
        });

        //绑定指定的端口 进行监听
        ChannelFuture f = b.bind(8765).sync(); 
        
        //Thread.sleep(1000000);
        f.channel().closeFuture().sync();
        
        bossGroup.shutdownGracefully();
        workerGroup.shutdownGracefully();
         
        
        
    }
    
}

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;


public class ServerHandler  extends ChannelHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    
            //do something msg
            ByteBuf buf = (ByteBuf)msg;
            byte[] data = new byte[buf.readableBytes()];
            buf.readBytes(data);
            String request = new String(data, "utf-8");
            System.out.println("Server: " + request);
            //写给客户端
            String response = "我是反馈的信息";
            ctx.writeAndFlush(Unpooled.copiedBuffer("888".getBytes()));
            //.addListener(ChannelFutureListener.CLOSE);
            

    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }

}

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

public class Client {

    public static void main(String[] args) throws Exception {
        
        EventLoopGroup workgroup = new NioEventLoopGroup();
        Bootstrap b = new Bootstrap();
        b.group(workgroup)
        .channel(NioSocketChannel.class)
        .handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(new ClientHandler());
            }
        });
        
        ChannelFuture cf1 = b.connect("127.0.0.1", 8765).sync();
        
        //buf
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("777".getBytes()));
        
        cf1.channel().closeFuture().sync();
        workgroup.shutdownGracefully();
        
    }
}

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.util.ReferenceCountUtil;

public class ClientHandler extends ChannelHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        try {
            //do something msg
            ByteBuf buf = (ByteBuf)msg;
            byte[] data = new byte[buf.readableBytes()];
            buf.readBytes(data);
            String request = new String(data, "utf-8");
            System.out.println("Client: " + request);
            
            
        } finally {
            ReferenceCountUtil.release(msg);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }

}