架构师养成记--19.netty

一、Netty初步

为什么选择Netty？

和NIO比较，要实现一个通信要简单得很多，性能很好。分布式消息中间件、storm、Dubble都是使用Netty作为底层通信。

Netty5.0要求jdk1.6以上。

http://netty.io

二、编码步骤

创建两个Nio线程组，一个事件处理，一个网络读写通信

创建一个ServerBootStrap，配置Netty参数；

创建实际处理的ChannelInitializer，进行初始化的准备工作，比如设置接收传出的字符集，格式，已经实际处理数据接口

绑定端口执行同步阻塞方法等待服务器端启动。

并发编程网 http://ifeve.com/netty5-user-guide

三、代码

服务端

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;

/**
 * Created by sgm on 2017/1/28.
 */
public class Server {
    public static void main(String []args) throws InterruptedException {
        /**
         * EventLoopGroup 事件组，不同的事件组处理不同的协议，这里使用NioEventLoopGroup来处理Tcp协议
         * 第一个事件循环组用来接收客户端信息，通常被称作boss，boos接收到信息后注册到worker上
         * 第二个事件循环组做实际的业务处理
         */
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        /**
         * 引导，对server进行一系列的配置
         */
        ServerBootstrap b = new ServerBootstrap();
        //将boss和worker关联起来
        b.group(bossGroup,workerGroup)
         .channel(NioServerSocketChannel.class)//使用的通道类型
         .childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel socketChannel) throws Exception {
                socketChannel.pipeline().addLast(new ServerHandler());
            }
         })//添加serverHandler，绑定具体的事件处理器
                /**
                 * 当客户端向客户端发送请求会带一个信号，服务器端返回一个信号并且将客户端的链接信息加入队列A中，
                 * 服务器再收到一个客户端的信号并且将客户端的信息从队列A移动到队列B中；
                 * 队列A和队列B的长度之和就是BACKLOG，如果大于了BACKLOG，tcp内核就会拒绝链接，BACKLOG只会影响到没有被accept取出的链接
                 */
         .option(ChannelOption.SO_BACKLOG,128)
         .option(ChannelOption.SO_KEEPALIVE,true);//保持连接
        ChannelFuture cf = b.bind(9876).sync();//绑定端口进行监听，异步的监听

        cf.channel().closeFuture().sync();//阻塞
        workerGroup.shutdownGracefully();
        bossGroup.shutdownGracefully();

    }
}

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

/**
 * Created by Administrator on 2017/1/28.
 */
public class ServerHandler 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("Server: " + request);
            //写给客户端
            String response = "我是反馈的信息";
            ctx.writeAndFlush(Unpooled.copiedBuffer("888".getBytes()));
        }finally {
            ReferenceCountUtil.release(msg);//有上一句话，即ctx.writeAndFlush()，这里可以不关闭
        }
    }

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

客户端

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", 9876).sync();

        //buf
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("777".getBytes()));

        cf1.channel().closeFuture().sync();
        workgroup.shutdownGracefully();

    }
}

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
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();
    }
}