netty 学习

这几天在学习netty ,将写的东西记一下.Netty是一个异步事件驱动的NIO框架，Netty的所有IO操作都是异步非阻塞的

client 

package com.example.demo.nettyLearning;

import io.netty.bootstrap.Bootstrap;
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;

import java.net.InetSocketAddress;

public class EchoClient {

    private final String host;
    private final int port;


    public EchoClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public static void main(String[] args) throws Exception {

        final String host ="127.0.0.1";
        final int port = 6666;

        new EchoClient(host, port).start();
    }

    public void start() throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {

            Bootstrap b = new Bootstrap();//1.创建 Bootstrap
            b.group(group)//2.指定 EventLoopGroup 来处理客户端事件。由于我们使用 NIO 传输，所以用到了 NioEventLoopGroup 的实现
                    .channel(NioSocketChannel.class)//3.使用的 channel 类型是一个用于 NIO 传输
                    .remoteAddress(new InetSocketAddress(host, port))//4.设置服务器的 InetSocketAddress
                    .handler(new ChannelInitializer<SocketChannel>() {//5.当建立一个连接和一个新的通道时，创建添加到 EchoClientHandler 实例 到 channel pipeline
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ch.pipeline().addLast(new EchoClientHandler());
                        }
                    });

            ChannelFuture f = b.connect().sync();//6.连接到远程;等待连接完成
            f.channel().closeFuture().sync();//7.阻塞直到 Channel 关闭

        } finally {

            group.shutdownGracefully().sync();//8.调用 shutdownGracefully() 来关闭线程池和释放所有资源
        }
    }
}

client handle 

package com.example.demo.nettyLearning;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.util.CharsetUtil;

/**
 * 客户端的工作内容：
 * 连接服务器
 * 发送信息
 * 发送的每个信息，等待和接收从服务器返回的同样的信息
 * 关闭连接
 */
@ChannelHandler.Sharable //1.@Sharable标记这个类的实例可以在 channel 里共享
public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {


    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.copiedBuffer("Netty rocks!",//2.当被通知该 channel 是活动的时候就发送信息
                CharsetUtil.UTF_8));
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
        System.out.println("Client received: " + in.toString(CharsetUtil.UTF_8));    //3 记录接收到的消息
    }


    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {//4.记录日志错误并关闭 channel
        cause.printStackTrace();
        ctx.close();
    }
}

server

package com.example.demo.nettyLearning;

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

public class EchoServer {

    private final int port;

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


    public static void main(String[] args) throws Exception {

        int port = 6666;//1.设置端口值（抛出一个 NumberFormatException 如果该端口参数的格式不正确）
        new EchoServer(port).start();//2.呼叫服务器的 start() 方法
    }

    public void start() throws Exception {

        NioEventLoopGroup group = new NioEventLoopGroup();//3.创建 EventLoopGroup
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(group)//4.创建 ServerBootstrap
                    .channel(NioServerSocketChannel.class)//5.指定使用 NIO 的传输 Channel
                    .localAddress(port)//6.设置 socket 地址使用所选的端口
                    .childHandler(new ChannelInitializer<SocketChannel>() {//7.添加 EchoServerHandler 到 Channel 的 ChannelPipeline

                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            socketChannel.pipeline().addLast(new EchoServerHandler());
                        }
                    });

            ChannelFuture f = b.bind().sync();//8.绑定的服务器;sync 等待服务器关闭
            System.out.println(EchoServer.class.getName() + " started and listen on " + f.channel().localAddress());
            f.channel().closeFuture().sync();//9.关闭 channel 和 块，直到它被关闭

        } finally {
            group.shutdownGracefully().sync();//10.关机的 EventLoopGroup，释放所有资源。
        }
    }
}

server handle

package com.example.demo.nettyLearning;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.util.CharsetUtil;


@ChannelHandler.Sharable //@Sharable 标识这类的实例之间可以在 channel 里面共享
public class EchoServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf in = (ByteBuf) msg;
        System.out.println("server received: " + in.toString(CharsetUtil.UTF_8));//日志消息输出到控制台
        ctx.write(in);//将所接收的消息返回给发送者。注意，这还没有冲刷数据
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.EMPTY_BUFFER)//冲刷所有待审消息到远程节点。关闭通道后，操作完成
                .addListener(ChannelFutureListener.CLOSE);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();//打印异常堆栈跟踪
        ctx.close();//关闭通道
    }
}