Netty服务端是如何一点一点被带动起来的(概略)

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

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

        // 这个线程用于接收客户端的连接
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        // 这4个线程用于处理IO读写
        EventLoopGroup workerGroup = new NioEventLoopGroup(8);
        // 这8个线程用于业务处理
        EventLoopGroup businessGroup = new NioEventLoopGroup(8);

        ServerBootstrap serverBootstrap = new ServerBootstrap();
        try {
            serverBootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<NioSocketChannel>() {
                        @Override
                        protected void initChannel(NioSocketChannel ch) {
                            ChannelPipeline channelPipeline = ch.pipeline();
                            channelPipeline.addLast(new StringEncoder());
                            channelPipeline.addLast(new StringDecoder());
                            channelPipeline.addLast(businessGroup, new ServerInHandler());
                        }
                    });

            // bind绑定
            ChannelFuture channelFuture = serverBootstrap.bind("127.0.0.1", 8080).sync();
            channelFuture.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

EventLoopGroup bossGroup = new NioEventLoopGroup(1);