Netty入门学习（六）：Netty如何满足Reactor模式的三种应用？

浅浅的花香味﹌ 2023-06-08 13:56 79阅读 0赞

##### 背景 #####

1.  Netty是Reactor模式的一个实践。
2.  Netty服务端如何做才能满足Reactor模式的三种应用？

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##### 服务端：Netty的标准使用 #####

1.  MyServer

public class MyServer {
    
        public static void main(String[] args) throws InterruptedException {
            EventLoopGroup bossGroup = new NioEventLoopGroup(1);
            EventLoopGroup workerGroup = new NioEventLoopGroup();
            try{
                ServerBootstrap serverBootstrap = new ServerBootstrap();
                serverBootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
                        .handler(new LoggingHandler(LogLevel.WARN))
                        .childHandler(new MyServerInitalizer());
                ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
                channelFuture.channel().closeFuture().sync();
            } finally {
                bossGroup.shutdownGracefully();
            }
    
        }
    }

1.  MyServerInitializer

public class MyServerInitializer extends ChannelInitializer<SocketChannel> {
    
        @Override
        protected void initChannel(SocketChannel ch) throws Exception {
            ChannelPipeline pipeline = ch.pipeline();
    
            //Netty自己提供的基础组件
            pipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 4, 0, 4));
            pipeline.addLast(new LengthFieldPrepender(4));
            pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
            pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
    
            //开发者自定义的handler
            pipeline.addLast("my server handler: ", new MyServerHandler());
    
        }
    }

1.  MyServerHandler

public class MyServerHandler extends SimpleChannelInboundHandler<String> {
    
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
    
            System.out.println(ctx.channel().remoteAddress() + ", " + msg);
            ctx.channel().writeAndFlush("from server: " + UUID.randomUUID());
        }
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
            cause.printStackTrace();
            ctx.close();
        }
    }

--------------------

##### Netty实现Reactor模式的单线程 #####

MyServer代码

public class MyServer {
    
        public static void main(String[] args) throws InterruptedException {
            EventLoopGroup bossGroup = new NioEventLoopGroup(1);
            try{
                ServerBootstrap serverBootstrap = new ServerBootstrap();
                serverBootstrap.group(bossGroup).channel(NioServerSocketChannel.class)
                        .handler(new LoggingHandler(LogLevel.WARN))
                        .childHandler(new MyServerInitializer());
                ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
                channelFuture.channel().closeFuture().sync();
            } finally {
                bossGroup.shutdownGracefully();
            }
    
        }
    }

##### Netty实现Reactor模式的多线程 #####

MyServer代码

public class MyServer {
    
        public static void main(String[] args) throws InterruptedException {
            EventLoopGroup bossGroup = new NioEventLoopGroup();
            try{
                ServerBootstrap serverBootstrap = new ServerBootstrap();
                serverBootstrap.group(bossGroup).channel(NioServerSocketChannel.class)
                        .handler(new LoggingHandler(LogLevel.WARN))
                        .childHandler(new MyServerInitializer());
                ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
                channelFuture.channel().closeFuture().sync();
            } finally {
                bossGroup.shutdownGracefully();
            }
    
        }
    }

1.  EventLoopGroup bossGroup = new NioEventLoopGroup();当我们的NioEventLoopGroup不添加参数的时候，其实就是多线程方式。
2.  Netty使用自定义的运行时类获取当前服务器的处理器个数，它的个数就是设置的线程数量。
3.  Netty获取线程数量的过程：  
    代码：  
    ![在这里插入图片描述][20191018161733242.png]  
    结果：  
    ![在这里插入图片描述][20191018161746655.png]  
    验证：  
    ![在这里插入图片描述][20191018161803207.png]

--------------------

##### Netty实现Reactor模式的主从模式 #####

MyServer代码：

public class MyServer {
    
        public static void main(String[] args) throws InterruptedException {
            EventLoopGroup bossGroup = new NioEventLoopGroup(1);
            EventLoopGroup workerGroup = new NioEventLoopGroup();
            try{
                ServerBootstrap serverBootstrap = new ServerBootstrap();
                serverBootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
                        .handler(new LoggingHandler(LogLevel.WARN))
                        .childHandler(new MyServerInitializer());
                ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
                channelFuture.channel().closeFuture().sync();
            } finally {
                bossGroup.shutdownGracefully();
            }
        }
    }

--------------------

##### 小结 #####

1.  整理Netty服务端的一个标准使用方式。
2.  整理Netty如何满足Reactor三种模式的应用。
3.  测试Netty的NettyRuntime.availableProcessors()的正确性。

[20191018161733242.png]: /images/20230531/9017260d6ec64fd3a0f13dbf3daf3b43.png
[20191018161746655.png]: /images/20230531/d666ab63127e4bfdbae06a5383472b1a.png
[20191018161803207.png]: /images/20230531/2d4d892b246e40e98e744e6872844775.png