从零学Netty（三）AIO通信（多人聊天室）

心已赠人 2022-12-13 04:56 308阅读 0赞

# AIO概念 #

异步非阻塞IO，全称AsynchronousI/O，JDK1.7升级了NIO类库，升级后的NIO类库被称为NIO2.0，也就是我们要介绍的AIO

NIO2.0引入了新的异步通道的概念，并提供了异步文件通道和异步套接字通道的实现。异步通道提供两种方式获取操作结果

它不需要通过多路复用器(Selector)对注册的通道进行轮询操作即可实现异步读写，从而简化了NIO的编程模型

# 原理图 #

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDQ2MTI4MQ_size_16_color_FFFFFF_t_70][]

图片来源：[https://mp.weixin.qq.com/s/CRd3-vRD7xwoexqv7xyHRw][https_mp.weixin.qq.com_s_CRd3-vRD7xwoexqv7xyHRw]

# 实例demo #

服务端代码

/**
     * aio服务端
     *
     * @author LionLi
     */
    public class AioServer {
    
        public void startListen(int port) throws Exception {
            ExecutorService executorService = Executors.newCachedThreadPool();
            AsynchronousChannelGroup channelGroup = AsynchronousChannelGroup.withThreadPool(executorService);
            AsynchronousServerSocketChannel serverSocketChannel = AsynchronousServerSocketChannel.open(channelGroup);
            serverSocketChannel.bind(new InetSocketAddress(port));
            // 接收并处理客户端请求
            serverSocketChannel.accept(null, new ServerHandler(serverSocketChannel));
    
        }
    
        public static void main(String[] args) throws Exception {
            AioServer aioServer = new AioServer();
            aioServer.startListen(8088);
            System.out.println("服务端正在监听.........");
            // 阻塞代码
            System.in.read();
        }
    }

服务端消息处理器代码

/**
     * aio服务端消息处理器
     *
     * @author LionLi
     */
    public class ServerHandler implements CompletionHandler<AsynchronousSocketChannel, Object> {
    
        // 客户端通道列表
        private static final List<AsynchronousSocketChannel> CHANNEL_LIST = new ArrayList<>();
        private final AsynchronousServerSocketChannel serverSocketChannel;
    
    
        public ServerHandler(AsynchronousServerSocketChannel serverSocketChannel) {
            this.serverSocketChannel = serverSocketChannel;
        }
    
        /**
         * 当实际IO操作完成时触发
         */
        @Override
        public void completed(AsynchronousSocketChannel result, Object attachment) {
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
            CHANNEL_LIST.add(result);
            serverSocketChannel.accept(null, this);
            result.read(byteBuffer, null, new CompletionHandler<Integer, Object>() {
                        @Override
                        public void completed(Integer result1, Object attachment) {
                            byteBuffer.flip();
                            // 获取消息输出
                            String msg = StandardCharsets.UTF_8.decode(byteBuffer).toString();
                            System.out.println("转发消息: " + msg);
    
                            // 分发消息
                            try {
                                for (AsynchronousSocketChannel asc : CHANNEL_LIST) {
                                    if (asc.isOpen()) {
                                        asc.write(ByteBuffer.wrap(msg.getBytes(StandardCharsets.UTF_8))).get();
                                    }
                                }
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                            byteBuffer.clear();
                            result.read(byteBuffer, null, this);
                        }
    
                        @Override
                        public void failed(Throwable exc, Object attachment) {
                            // 从该Channel中读取数据失败，将该Channel删除
                            CHANNEL_LIST.remove(result);
                        }
                    }
            );
        }
    
        @Override
        public void failed(Throwable exc, Object attachment) {
            exc.printStackTrace();
        }
    }

客户端代码

/**
     * aio客户端
     *
     * @author LionLi
     */
    public class AioClient {
    
        private final ExecutorService executorService;
        // 连接通道
        private AsynchronousSocketChannel socketChannel;
        private AsynchronousChannelGroup channelGroup;
        private final String username;
    
        public AioClient(String ip, int port, String username) {
            this.username = username;
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
            executorService = Executors.newCachedThreadPool();
            try {
                channelGroup = AsynchronousChannelGroup.withThreadPool(executorService);
                socketChannel = AsynchronousSocketChannel.open(channelGroup);
                // 连接到远程服务器
                socketChannel.connect(new InetSocketAddress(ip, port)).get();
                send("上线了");
                byteBuffer.clear();
                socketChannel.read(byteBuffer, null, new CompletionHandler<Integer, Object>() {
                    @Override
                    public void completed(Integer result, Object attachment) {
                        byteBuffer.flip();
                        // 将buff中的内容转换成字符串
                        String content = StandardCharsets.UTF_8.decode(byteBuffer).toString();
                        // 显示从服务器端读取的数据
                        System.out.println(content);
                        byteBuffer.clear();
                        socketChannel.read(byteBuffer, null, this);
                    }
    
                    @Override
                    public void failed(Throwable exc, Object attachment) {
                        exc.printStackTrace();
                    }
                });
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    
        public void send(String msg) {
            msg = username + "：" + msg;
            try {
                socketChannel.write(ByteBuffer.wrap(msg.getBytes(StandardCharsets.UTF_8))).get();
            } catch (InterruptedException | ExecutionException e) {
                e.printStackTrace();
            }
        }
    
        public static void main(String[] args) {
            System.out.print("请输入用户名: ");
            Scanner scanner = new Scanner(System.in);
            String username = scanner.nextLine();
            AioClient client = new AioClient("localhost", 8088, username);
            while (true) {
                // 发送数据到服务端
                String msg = scanner.nextLine();
                if (msg.equals("exit")) {
                    client.send("下线了");
                    client.channelGroup.shutdown();
                    client.executorService.shutdown();
                    break;
                } else {
                    client.send(msg);
                }
            }
        }
    }

# 测试 #

*  场景如下：
 *  启动服务端
 *  顺序启动客户端 用户ABC 并输入用户名
 *  分别打招呼
 *  倒序退出客户端 用户ABC

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDQ2MTI4MQ_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDQ2MTI4MQ_size_16_color_FFFFFF_t_70 2][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDQ2MTI4MQ_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDQ2MTI4MQ_size_16_color_FFFFFF_t_70 4][]

项目已上传到gitee

地址: [netty-demo][]

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[https_mp.weixin.qq.com_s_CRd3-vRD7xwoexqv7xyHRw]: https://mp.weixin.qq.com/s/CRd3-vRD7xwoexqv7xyHRw
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MDQ2MTI4MQ_size_16_color_FFFFFF_t_70 1]: /images/20221123/8b686c9adb6b4c2db285fe305fcf8f27.png
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[netty-demo]: https://gitee.com/JavaLionLi/LionLi-Labs/tree/master/netty-demo