Netty入门学习（六）：Netty如何满足Reactor模式的三种应用？

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本文链接： https://blog.csdn.net/outsanding/article/details/102627442

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();
        }

    }
}

2. 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());

    }
}

3. 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：
   
   结果：
   
   验证：
   

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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。