构建Netty的第一个服务器Hello Netty

àì夳堔傛蜴生んèń 2021-11-11 07:32 267阅读 0赞

### 概述 ###

使用主从线程模型搭建服务器

*  构建一对主从线程组
 *  定义服务器启动类
 *  为服务器设置Channel(每一个客户端需要在服务端注册一个channel数据通道)
 *  设置处理 从线程池 的助手类初始化器(处理子线程组助手类handler)
 *  监听启动和关闭服务器

### 步骤 ###

绑定8088端口，采用不指定路由的方式，即所有访问localhost:8088的路由都能返回Hello Netty(比如localhost:8088/test)

创建Maven项目，pom中添加依赖(<dependencies></dependencies>中)

<dependency>
        <groupId>io.netty</groupId>
        <artifactId>netty-all</artifactId>
        <version>4.1.37.Final</version>
    </dependency>

主体类(含有main方法) HelloServer.java

package com.imooc.netty;
    
    import io.netty.bootstrap.ServerBootstrap;
    import io.netty.channel.ChannelFuture;
    import io.netty.channel.EventLoopGroup;
    import io.netty.channel.nio.NioEventLoop;
    import io.netty.channel.nio.NioEventLoopGroup;
    import io.netty.channel.socket.nio.NioServerSocketChannel;
    
    /**
     * @Author Sakura
     * @Date 5/8/2019
     * @Description 客户端发送一个请求，服务端返回Hello Netty
     **/
    public class HelloServer {
    
        public static void main(String[] args) throws Exception {
    
            //定义一对线程组
            //主线程组，接收客户端连接
            EventLoopGroup bossGroup = new NioEventLoopGroup();
            //从线程组，处理事件
            EventLoopGroup workerGroup = new NioEventLoopGroup();
    
            try {
                //服务器创建，ServerBootstrap是启动类
                ServerBootstrap serverBootstrap = new ServerBootstrap();
                serverBootstrap.group(bossGroup,workerGroup)  //设置主从线程组
                        .channel(NioServerSocketChannel.class) //设置NIO双向通道
                        .childHandler(new HelloServerInitialiizer()); //子处理器，处理workerGroup
    
                //启动server，绑定8088端口，启动方式为同步
                ChannelFuture channelFuture = serverBootstrap.bind(8088).sync();
    
                //监听关闭的channel，设置为同步方式
                channelFuture.channel().closeFuture().sync();
            } finally {
                bossGroup.shutdownGracefully();
                workerGroup.shutdownGracefully();
            }
        }
    
    }

初始化器 HelloServerInitialiizer.java

package com.imooc.netty;
    
    import io.netty.channel.ChannelInitializer;
    import io.netty.channel.ChannelPipeline;
    import io.netty.channel.socket.SocketChannel;
    import io.netty.handler.codec.http.HttpServerCodec;
    
    /**
     * @Author Sakura
     * @Date 5/8/2019
     * @Description 初始化器，channel注册后，执行相应初始化方法
     **/
    public class HelloServerInitialiizer  extends ChannelInitializer<SocketChannel> {
    
        protected void initChannel(SocketChannel socketChannel) throws Exception {
    
            //通过socketChannel获得对应管道
            ChannelPipeline channelPipeline = socketChannel.pipeline();
    
            //通过管道，添加handler
            //HttpServerCodec是由Netty 提供的助手类。请求来到服务端时解码，响应到客户端时编码
            channelPipeline.addLast("HttpServerCodec",new HttpServerCodec());
    
            //添加自定义助手类，返回"hello netty"
            channelPipeline.addLast("customHandler",new CustomHandler());
        }
    }

返回Hello Netty的助手类  CustomHandler.java

package com.imooc.netty;
    
    import io.netty.buffer.ByteBuf;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.Channel;
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.channel.SimpleChannelInboundHandler;
    import io.netty.handler.codec.http.*;
    import io.netty.util.CharsetUtil;
    
    
    /**
     * @Author Sakura
     * @Date 5/8/2019
     * 创建自定义助手类
     **/
    
    //SimpleChannelInboundHandler：对于请求，相当于[入站]
    public class CustomHandler extends SimpleChannelInboundHandler<HttpObject> {
        protected void channelRead0(ChannelHandlerContext channelHandlerContext, HttpObject httpObject) throws Exception {
    
            //获取channel
            Channel channel = channelHandlerContext.channel();
    
            //仅处理HttpRequest请求
            if(httpObject instanceof HttpRequest){
                //显示客户端远程地址
                System.out.println(channel.remoteAddress());
    
                //定义发送的数据
                ByteBuf content = Unpooled.copiedBuffer("Hello Netty~", CharsetUtil.UTF_8);
    
                //构建一个http response
                FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1,
                        HttpResponseStatus.OK,content);
                //为响应增加数据类型和长度
                response.headers().set(HttpHeaderNames.CONTENT_TYPE,"text/plain");
                response.headers().set(HttpHeaderNames.CONTENT_LENGTH,content.readableBytes());
    
                //把响应刷新到客户端
                channelHandlerContext.writeAndFlush(response);
    
            }
    
        }
    }

### 测试 ###

启动项目后，浏览器输入localhost:8088

![20190805150223977.png][]

控制台显示

![20190805150248844.png][]

为什么显示两条那，打开请求网页的开发者工具，network栏目，刷新网页重新请求，发现有两条请求(下边的请求为图标请求)

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA4OTE3NQ_size_16_color_FFFFFF_t_70][]

可以使用命令行(cmd)进行纯净的请求

![20190805150524277.png][]

此时控制台只有一条

![20190805150601163.png][]

[20190805150223977.png]: /images/20211109/7032b37604d8427e9c291117e3ec4ec6.png
[20190805150248844.png]: /images/20211109/6a87133002554652b2b5e00dc65350c7.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA4OTE3NQ_size_16_color_FFFFFF_t_70]: /images/20211109/551c968351124461bc05dd84d13dffb9.png
[20190805150524277.png]: /images/20211109/0b2043decd94487899cc172a23c5de9d.png
[20190805150601163.png]: /images/20211109/68ff6252d9404fbc9215e4412cac4fc2.png