Hello Netty 服务

• 构建一对主从线程组

• 定义服务器启动类

• 为服务器设置Channel

• 设置从线程池的助手类初初始化器

• 监听启动和关闭服务器

代码

1.导入依赖

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
    <version>4.1.25.Final</version>
</dependency>

2.编写主从线程组启动类

/**
 * @author: webin
 * @date: 2020/4/3 21:59
 * @description: 实现客户端发送一个请求,服务器会返回一个 hello netty
 * @version: 0.0.1
 */
public class HelloServer {

    public static void main(String[] args) throws InterruptedException {

        // 定义一对线程组
        // 主线程组 用于接收客户端的连接,但是不做任何处理
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        // 从线程组 主线程组会把任务丢给从线程组,从线程组去做事
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            // netty服务器的创建,serverBootstrap是一个启动类
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup,workerGroup)    //设置主从线程组
                    .channel(NioServerSocketChannel.class) // 设置nio的双线通道
                    .childHandler(new HelloServerInitializer());                    // 用于处理workerGroup的线程

            // 启动server,并设置8088为启动端口,同时启动方式为同步
            ChannelFuture channelFuture = serverBootstrap.bind(8080).sync();// 设置同步
            // 用于监听关闭的channel
            channelFuture.channel().closeFuture().sync();
            System.out.println("关闭");
        } finally {
            // 关闭服务器
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

3. 定义初始化器

/**
 * @author: webin
 * @date: 2020/4/3 22:31
 * @description: 初始化器,channel注册后,会执行里面相应的初始化方法
 * @version: 0.0.1
 */
public class HelloServerInitializer extends ChannelInitializer<SocketChannel> {

    @Override
    protected void initChannel(SocketChannel socketChannel) throws Exception {
        // 通过SocketChannel去获取对应的管道
        ChannelPipeline pipeline = socketChannel.pipeline();
        // HttpServerCodec是由netty自己提供的助手类,可以理解为拦截器
        // 当请求到服务器,我们需要做解码,响应到客户端需要编码
        pipeline.addLast("HttpServerCodec",new HttpServerCodec()); // 通过管道添加了一个handler

        pipeline.addLast("customHandler",new CustomHandler());

    }
}

4. 自定义处理器

/**
 * @author: webin
 * @date: 2020/4/3 22:38
 * @description: 创建自定义助手类,
 *  SimpleChannelInboundHandler: 对于请求来讲,其实相当于入站
 * @version: 0.0.1
 */
public class CustomHandler extends SimpleChannelInboundHandler {

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel .. 添加");
        super.handlerAdded(ctx);
    }

    /**
     * channel注册
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel ... 注册");
        super.channelRegistered(ctx);
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel ... 连接");
        super.channelActive(ctx);
    }


    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Object o) throws Exception {
        // 获取channel
        Channel channel = ctx.channel();
        if (o instanceof HttpRequest)
            System.out.println(channel.remoteAddress());

        // 定义发送数据的消息
        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);
        // 未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
        ctx.writeAndFlush(response);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel ... 读取完毕");
        super.channelReadComplete(ctx);
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel ... 不活跃状态");
        super.channelInactive(ctx);
    }

    @Override
    public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel ... 销毁");
        super.channelUnregistered(ctx);
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel .. 移除");
        super.handlerRemoved(ctx);
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        System.out.println("channel ... 事件触发");
        super.userEventTriggered(ctx, evt);
    }

    @Override
    public void channelWritabilityChanged(ChannelHandlerContext ctx) throws Exception {
        System.out.println("channel ... 可写可更改");
        super.channelWritabilityChanged(ctx);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        System.out.println("channel ... 捕获到异常");
        super.exceptionCaught(ctx, cause);
    }
}

Hello Netty

原文：https://www.cnblogs.com/smallwolf/p/12630881.html