<!-- https://mvnrepository.com/artifact/io.netty/netty-all -->
<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.68.Final</version>
</dependency>

package com.guor.demo.netty;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

/**
 * 主程序類(lèi)
 */
public class MyNettyServerTest {
    public static void main(String[] args) throws InterruptedException {
        /**
         * EventLoopGroup：事件循環(huán)組，是一個(gè)線程池，也是一個(gè)死循環(huán)，用于不斷地接收用戶(hù)請(qǐng)求；
         * serverGroup：用戶(hù)監(jiān)聽(tīng)及建立連接，并把每一個(gè)連接抽象為一個(gè)channel，最后再將連接交給clientGroup處理；
         * clientGroup：真正的處理連接
         */
        EventLoopGroup serverGroup = new NioEventLoopGroup();
        EventLoopGroup clientGroup = new NioEventLoopGroup();
        try {
            // 服務(wù)端啟動(dòng)時(shí)的初始化操作
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            // 1、將serverGroup和clientGroup注冊(cè)到服務(wù)端的Channel上；
            // 2、注冊(cè)一個(gè)服務(wù)端的初始化器MyNettyServerInitializer；
            // 3、該初始化器中的initChannel()方法會(huì)在連接被注冊(cè)到Channel后立刻執(zhí)行；
            // 5、最后將端口號(hào)綁定到8080；
            ChannelFuture channelFuture = serverBootstrap.group(serverGroup, clientGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new MyNettyServerInitializer()).bind(8080).sync();
            channelFuture.channel().closeFuture().sync();
        }catch (Exception e){
            System.out.println(e);
        }finally {
            serverGroup.shutdownGracefully();
            clientGroup.shutdownGracefully();
        }
    }
}

package com.guor.demo.netty;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpServerCodec;

/**
 * 初始化器
 */
public class MyNettyServerInitializer extends ChannelInitializer<SocketChannel> {

    // 連接被注冊(cè)到Channel后，立刻執(zhí)行此方法
    @Override
    protected void initChannel(SocketChannel socketChannel) throws Exception {
        ChannelPipeline pipeline = socketChannel.pipeline();
        // 加入netty提供的處理器
        pipeline.addLast("HttpServerCodec",new HttpServerCodec());
        // 增加自定義處理器MyNettyServerHandler，用于實(shí)際處理請(qǐng)求，并給出響應(yīng)
        pipeline.addLast("MyNettyServerHandler",new MyNettyServerHandler());
    }
}

package com.guor.demo.netty;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.*;
import io.netty.util.CharsetUtil;

/**
 * 自定義處理器
 * Inbound代表"進(jìn)入"的請(qǐng)求
 */
public class MyNettyServerHandler extends SimpleChannelInboundHandler<HttpObject> {

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, HttpObject httpObject) throws Exception {
        // 定義響應(yīng)的內(nèi)容
        ByteBuf byteBuf = Unpooled.copiedBuffer("Hello Netty", CharsetUtil.UTF_8);
        DefaultFullHttpResponse defaultFullHttpResponse = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, byteBuf);
        defaultFullHttpResponse.headers().set(HttpHeaderNames.CONTENT_TYPE,"text/plain");
        byteBuf.readableBytes();
        // 等響應(yīng)返回給客戶(hù)端
        channelHandlerContext.writeAndFlush(defaultFullHttpResponse);
    }
}

package com.guor.demo.netty;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.*;
import io.netty.util.CharsetUtil;

/**
 * 自定義處理器
 * Inbound代表"進(jìn)入"的請(qǐng)求
 */
public class MyNettyServerHandler extends SimpleChannelInboundHandler<HttpObject> {

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, HttpObject httpObject) throws Exception {
        // 定義響應(yīng)的內(nèi)容
        ByteBuf byteBuf = Unpooled.copiedBuffer("Hello Netty", CharsetUtil.UTF_8);
        DefaultFullHttpResponse defaultFullHttpResponse = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, byteBuf);
        defaultFullHttpResponse.headers().set(HttpHeaderNames.CONTENT_TYPE,"text/plain");
        byteBuf.readableBytes();
        // 等響應(yīng)返回給客戶(hù)端
        channelHandlerContext.writeAndFlush(defaultFullHttpResponse);
    }

    /**
     * 增加新處理器時(shí)，觸發(fā)此方法
     */
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception{
        System.out.println("1、handlerAdded、增加了新的處理器");
        super.handlerAdded(ctx);
    }

    /**
     * 當(dāng)通道被注冊(cè)到一個(gè)事件循環(huán)組EventLoop上時(shí)，觸發(fā)此方法
     */
    @Override
    public void channelRegistered(ChannelHandlerContext ctx) throws Exception{
        System.out.println("2、channelRegistered、通道被注冊(cè)");
        super.channelRegistered(ctx);
    }

    /**
     * 當(dāng)遠(yuǎn)端處于活躍狀態(tài)時(shí)（連接到了某個(gè)遠(yuǎn)端，可以收發(fā)數(shù)據(jù)），執(zhí)行此方法
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception{
        System.out.println("3、channelActive、通道連接到了遠(yuǎn)端，處于活躍狀態(tài)");
        super.channelActive(ctx);
    }

    /**
     * 當(dāng)通道處于非活躍狀態(tài)時(shí)（與遠(yuǎn)端斷開(kāi)了連接），執(zhí)行此方法
     */
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception{
        System.out.println("4、channelInactive、通道遠(yuǎn)端斷開(kāi)了連接，處于非活躍狀態(tài)");
        super.channelInactive(ctx);
    }

    /**
     * 當(dāng)通道被取消了注冊(cè)時(shí)，執(zhí)行此方法
     */
    @Override
    public void channelUnregistered(ChannelHandlerContext ctx) throws Exception{
        System.out.println("5、channelUnregistered、通道被取消了注冊(cè)");
        super.channelUnregistered(ctx);
    }

    /**
     * 當(dāng)程序發(fā)生異常，執(zhí)行此方法
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx,Throwable e) throws Exception{
        System.out.println("6、exceptionCaught、程序發(fā)生了異常");
        e.printStackTrace();
        ctx.close();
    }
}