依赖引入

		<dependency>
			<groupId>io.netty</groupId>
			<artifactId>netty-all</artifactId>
			<netty.version>4.1.22.Final</netty.version>
		</dependency>

编写服务端

业务类HttpServerChannelHandler

public class HttpServerChannelHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
    
    protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest msg) throws Exception {
        ctx.channel().remoteAddress();
        
        FullHttpRequest request = msg;
        
        System.out.println("请求方法名称为：" + request.method().name());
        
        System.out.println("uri:" + request.uri());
        
        ByteBuf buf = request.content();
        
        System.out.println(buf.toString(CharsetUtil.UTF_8));
        
        ByteBuf byteBuf = Unpooled.copiedBuffer("hello world", CharsetUtil.UTF_8);
        FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK,byteBuf);
        response.headers().add(HttpHeaderNames.CONTENT_TYPE, "text/plain");
        response.headers().add(HttpHeaderNames.CONTENT_LENGTH, byteBuf.readableBytes());
        
        ctx.writeAndFlush(response);
        
    }

}

业务类需要实现SimpleChannelInboundHandler
只需要实现一个方法channelRead0即可
该方法是获取客户端请求，然后处理，再响应给客户端，是不是和我们使用springboot写接口类似

编写注册类HttpServerInitializer

接下来我们将编写注册类，这里与编写echo服务器有所区别，echo是隐式创建了注册类，这里是显式。

public class HttpServerInitializer extends ChannelInitializer<SocketChannel> {

    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        //处理http消息的编解码
        pipeline.addLast("httpServerCodec", new HttpServerCodec());
        pipeline.addLast("aggregator", new HttpObjectAggregator(65536));
        //添加自定义的ChannelHandler
        pipeline.addLast("httpServerHandler", new HttpServerChannelHandler());
    }

}

该类需要实现ChannelInitializer
然后我们重写了initChannel方法，将服务类HttpServerChannelHandler添加进channel
另外我们可以看到，会比echo服务多出了两个类HttpServerCodec、HttpObjectAggregator，这两个是netty提供的http编解码相关的类
这两个类有什么用呢？
可以看到服务类那里FullHttpRequest（解码的来）、FullHttpResponse（会被编码）两个对象，这两个对象就是都会经过HttpServerCodec编码器编码和解码。

编写启动类HttpServer

public class HttpServer {
    public static void main(String[] args) {
      //构造两个线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            //服务端启动辅助类
            ServerBootstrap bootstrap = new ServerBootstrap();
 
            bootstrap.group(bossGroup, workerGroup)
            .channel(NioServerSocketChannel.class)
            .childHandler(new HttpServerInitializer());
 
            ChannelFuture future = bootstrap.bind(8080).sync();
            //等待服务端口关闭
            future.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            // 优雅退出，释放线程池资源
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}