Netty5:Netty模型

1、Netty工作原理示意图1

Netty主要基于主从Reactors多线程模型做了一定改进，具有多个Reactor;

1. BossGroup线程维护Selector,只关注Accept;
2. 当接收到Accept事件，获取到对应的SocketChannel,封装成NIOSocketChannel并注册到Worker线程，并进行维护；
3. 当worker线程监听到selector中通道发生自己感兴趣的事件后，就由handler进行处理；

2、Netty工作原理示意图2

3、Netty工作原理图3

1. Netty抽象出两组线程池：BossGroup专门负责接收客户端的连接，WorkerGroup专门负责网络的读写；他们都是NioEventLoopGroup;
2. NioEventLoopGroup相当于一个事件循环组，这个组中含有多个事件循环，每一个都是NioEventLoop;
3. NioEventLoop表示一个不断循环的执行处理任务的线程，每一个NioEventLoop都有一个selector，用于监听绑定在其上的socket网络通讯；
4. NioEventLoopGroup可以有多个线程，即含有多个NioEventLoop；
5. 每个Boss NioEventLoop循环执行的步骤包括三步：

轮询accept事件；
处理accept事件，与client建立连接，生成NioSocketChannel，并将其注册到某个Worker NioEventLoop的selector;
处理任务队列的任务，即runAllTasks

6. Worker NioEventLoop循环执行的步骤：

轮询read,write事件
处理io事件，即read/write事件，在对应的NioSocketChannel处理；
处理任务队列的任务，即runAllTasks;

7. 每个worker NioEventLoop处理业务时，会使用pipeline(管道)，里面包含了channel，即通过pipeline可以获取到对应通道，管道中维护了很多的handler;

4、Netty实例-TCP服务

package gyx.netty.simple;

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;

public class NettyServer {
    
    
    public static void main(String[] args) throws InterruptedException {
    
    
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try{
    
    
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(bossGroup,workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG,128)
                    .childOption(ChannelOption.SO_KEEPALIVE,true)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
    
    
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
    
    
                            ch.pipeline().addLast(new NettyServerHandler());
                        }
                    });
            System.out.println(".....服务器 is ready...");
            ChannelFuture cf = bootstrap.bind(6668).sync();
            cf.channel().closeFuture().sync();
        }finally{
    
    
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}


package gyx.netty.simple;

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

public class NettyServerHandler extends ChannelInboundHandlerAdapter {
    
    
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    
    
        System.out.println("服务器读取线程 "+Thread.currentThread().getName());
        System.out.println("server ctx="+ctx);
        Channel channel = ctx.channel();
        ByteBuf buf=(ByteBuf)msg;
        System.out.println("客户端发送消息是："+buf.toString(CharsetUtil.UTF_8));
        System.out.println("客户端地址："+channel.remoteAddress());
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
    
    
        ctx.writeAndFlush(Unpooled.copiedBuffer("hello,client",CharsetUtil.UTF_8));
    }

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

package gyx.netty.simple;

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;

public class NettyClient {
    
    
    public static void main(String[] args) throws InterruptedException {
    
    
        EventLoopGroup group = new NioEventLoopGroup();
        try{
    
    
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
    
    
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
    
    
                            ch.pipeline().addLast(new NettyClientHandler());
                        }
                    });
            System.out.println("client ok..");
            ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 6668).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
    
    
            group.shutdownGracefully();
        }
    }
}

package gyx.netty.simple;

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

public class NettyClientHandler extends ChannelInboundHandlerAdapter {
    
    
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    
    
        System.out.println("client "+ctx);
        ctx.writeAndFlush(Unpooled.copiedBuffer("hello,server", CharsetUtil.UTF_8));
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    
    
        ByteBuf buf=(ByteBuf)msg;
        System.out.println("服务器回复的消息："+buf.toString(CharsetUtil.UTF_8));
        System.out.println("服务器地址："+ctx.channel().remoteAddress());
    }

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