Netty初探

终于要开始用netty，经过我前面的介绍的java的I/O历程，是不是很纠结，nio固然很好，就是用起来太麻烦。怎么办？netty来帮忙！
步骤：

1.下载jar包

我用的是maven，所以在这里就贴出dependency

        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>5.0.0.Alpha1</version>
        </dependency>

等待依赖下载完成。

2.服务端

以一个时间服务器为例，客户端发出”order”请求，服务端返回当前时间。

TimeServer:

package com.dubby.server;

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 dubby on 16/3/20. */
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
            ChannelFuture f = b.bind(port).sync();

            //等待服务端监听监听端口关闭
            f.channel().closeFuture().sync();
        } finally {
            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;
        new TimeServer().bind(port);
    }

}

TimeServerHandler：

package com.dubby.server;

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

import java.util.Date;

/** * Created by dubby on 16/3/20. */
public class TimeServerHandler extends ChannelHandlerAdapter {
    @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".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();
    }
}

OK，服务端代码就这些。

3.客户端

TimeClient

package com.dubby.client;

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 dubby on 16/3/20. */
public class TimeClient {
    public void connect(int port,String host) throws Exception{
        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();

            //等待客户端关闭连接
            f.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception{
        int port = 8080;
        new TimeClient().connect(port,"127.0.0.1");
    }
}

TimeClientHandler：

package com.dubby.client;

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

import java.util.logging.Logger;

/** * Created by dubby on 16/3/20. */
public class TimeClientHandler extends ChannelHandlerAdapter {
    private static final Logger logger = Logger.getLogger(TimeClientHandler.class.getName());

    private ByteBuf firstMessage;

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

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(firstMessage);
    }

    @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("Now is : "+body);
    }

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

客户端完成了。可以测试了。