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Netty学习

Netty是什么

Netty是一个异步事件驱动的网络应用程序框架,用于快速开发可维护的高性能协议服务器和客户端。

Netty架构

Transport Services 支持Socket等多种传输方式。

Protocol Support 提供多协议的编解码。

Core 核心设计包含事件处理模型、API的使用、ByteBuffer的增强

核心组件

Channel:Netty定义的Channel,增强版的通道

EventLoop: 由线程驱动,处理channel的所有I/O事件

ChannelPipeline: 事件处理机制

ChannelHandler: 事件处理器

ByteBuffer: 增强的缓冲区

Bootstrap: 启动类,引导Netty应用程序启动

简单的Netty 使用springboot写个demo

引入netty包

        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.34.Final</version>
        </dependency>
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服务端

public final class EchoServer {

    static final int PORT = Integer.parseInt(System.getProperty("port", "8007"));

    public static void main(String[] args) throws Exception {
        // 1、创建EventLoopGroup
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        final EchoServerHandler serverHandler = new EchoServerHandler();
        try {
            // 2、创建启动器
            ServerBootstrap b = new ServerBootstrap();
            // 3、配置启动器
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 100)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();
                            //p.addLast(new LoggingHandler(LogLevel.INFO));
                            p.addLast(serverHandler);
                        }
                    });

            // 4、启动器启动器
            ChannelFuture f = b.bind(PORT).sync();

            // 5、等待服务端channel关闭
            f.channel().closeFuture().sync();
        } finally {
            // 6.释放资源
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}
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定义服务端的Handler

@Sharable
public class EchoServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        System.out.println("收到客户端数据,还给客户端:" + msg);
        ctx.write(msg);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // Close the connection when an exception is raised.
        cause.printStackTrace();
        ctx.close();
    }
}
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客户端代码

public final class EchoClient {

    static final String HOST = System.getProperty("host", "127.0.0.1");
    static final int PORT = Integer.parseInt(System.getProperty("port", "8007"));
    static final int SIZE = Integer.parseInt(System.getProperty("size", "256"));

    public static void main(String[] args) throws Exception {
        // Configure the client.
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();
                            //p.addLast(new LoggingHandler(LogLevel.INFO));
                            p.addLast(new EchoClientHandler());
                        }
                    });

            // Start the client.
            ChannelFuture f = b.connect(HOST, PORT).sync();

            // Wait until the connection is closed.
            f.channel().closeFuture().sync();
        } finally {
            // Shut down the event loop to terminate all threads.
            group.shutdownGracefully();
        }
    }
}
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客户端的的Handler

public class EchoClientHandler extends ChannelInboundHandlerAdapter {

    private final ByteBuf firstMessage;

    /**
     * Creates a client-side handler.
     */
    public EchoClientHandler() {
        firstMessage = Unpooled.buffer(EchoClient.SIZE);
        for (int i = 0; i < firstMessage.capacity(); i++) {
            firstMessage.writeByte((byte) i);
        }
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        System.out.println("给服务器发送数据:" + firstMessage);
        ctx.writeAndFlush(firstMessage);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        System.out.println("收到服务端数据,还给服务器:" + msg);
        ctx.write(msg);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // Close the connection when an exception is raised.
        cause.printStackTrace();
        ctx.close();
    }
}
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最简单的demo到此结束。

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