Netty入门应用

使用JDK的NIO类库开发程序步骤十分繁琐，而且容易出错。下面使用netty进行入门开发

本例使用netty 4.0的jar包（netty 5.0由于各种原因被原作者放弃）

netty jar包下载地址http://download.youkuaiyun.com/detail/hueason/9832925

package com.hueason.netty.n2.simpledemo;

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

/**
 * Created by Administrator on 2017/4/20.
 */
public class TimeServer {
    public void bind(int port) throws Exception {
        //配置服务端的NIO线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 1024)
                    .childHandler(new ChildChannelHandler());

            //绑定端口，同步等待成功  完成之后会返回ChannelFuture用于异步操作的通知回调
            ChannelFuture f = b.bind(port).sync();
            //等待服务器监听端口关闭
            f.channel().closeFuture().sync();
        } finally {
            //优雅退出，释放线程池资源
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    private class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
        @Override
        protected void initChannel(SocketChannel socketChannel) throws Exception {
            socketChannel.pipeline().addLast(new TimeServerHandler());
        }
    }

    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args != null && args.length > 0){
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                e.printStackTrace();
            }
        }
        new TimeServer().bind(port);
    }
}

package com.hueason.netty.n2.simpledemo;


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

import java.util.Date;

/**
 * Created by Administrator on 2017/4/20.
 */
public class TimeServerHandler extends ChannelInboundHandlerAdapter{
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req,"UTF-8");
        System.out.println("The time server receive order "+body);
        String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body)?new Date(System.currentTimeMillis()).toString():"BAD ORDER";
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.write(resp);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.flush();
    }

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

客户端

package com.hueason.netty.n2.simpledemo;

import io.netty.bootstrap.Bootstrap;
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.NioSocketChannel;

/**
 * Created by Administrator on 2017/4/26.
 */
public class TimeClient {
    public void connect(int port,String host) throws InterruptedException {
        //配置客户端NIO线程组
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY,true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            socketChannel.pipeline().addLast(new TimeClientHandler());
                        }
                    });
            //发起异步连接操作
            ChannelFuture f = b.connect(host,port).sync();
            //等待客户端链路关闭
            f.channel().closeFuture().sync();
        }finally {
            //优雅退出，释放NIO线程组
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws InterruptedException {
        int port = 8080;
        if(args != null && args.length >0){
            port = Integer.valueOf(args[0]);

        }

        new TimeClient().connect(port,"127.0.0.1");
    }
}

package com.hueason.netty.n2.simpledemo;

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

import java.util.logging.Logger;

/**
 * Created by Administrator on 2017/4/26.
 */
public class TimeClientHandler extends ChannelInboundHandlerAdapter {
    private static final Logger logger = Logger.getLogger(TimeClientHandler.class.getName());
    private final ByteBuf firstMessage;


    public TimeClientHandler() {
        byte[] req = "QUERY TIME ORDER".getBytes();
        this.firstMessage = Unpooled.buffer(req.length);
        firstMessage.writeBytes(req);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        //释放资源
        logger.warning("Unexpected exception from downstream :" + cause.getMessage());
        ctx.close();
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {//服务端返回应答时，该方法被调用
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("Now is :" + body);
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {//客户端和服务端的TCP链路建立成功之后，Netty的NIO线程会调用该方法
        ctx.writeAndFlush(firstMessage);
    }
}

相比于http://blog.youkuaiyun.com/hueason/article/details/71082084传统NIO开发难度大大降低