【九月打卡】第16天 解锁网络编程之NIO的前世今生

课程名称： 解锁网络编程之NIO的前世今生

课程章节：第4章 【应用】NIO网络编程实战、第5章 【掌握】NIO网络编程缺陷

课程讲师： 张小喜

课程内容：

服务器端补充对其他客户端的广播

private void broadCast(Selector selector,
                           SocketChannel sourceChannel, String request) {
        /**
         * 获取到所有已接入的客户端channel
         */
        Set<SelectionKey> selectionKeySet = selector.keys();

        /**
         * 循环向所有channel广播信息
         */
        selectionKeySet.forEach(selectionKey -> {
            Channel targetChannel = selectionKey.channel();

            // 剔除发消息的客户端
            if (targetChannel instanceof SocketChannel
                    && targetChannel != sourceChannel) {
                try {
                    // 将信息发送到targetChannel客户端
                    ((SocketChannel) targetChannel).write(
                            Charset.forName("UTF-8").encode(request));
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }

客户端的写法

    public void start(String nickname) throws IOException {
        /**
         * 连接服务器端
         */
        SocketChannel socketChannel = SocketChannel.open(
                new InetSocketAddress("127.0.0.1", 8000));

        /**
         * 接收服务器端响应
         */
        // 新开线程，专门负责来接收服务器端的响应数据
        // selector ， socketChannel ， 注册
        Selector selector = Selector.open();
        socketChannel.configureBlocking(false);
        socketChannel.register(selector, SelectionKey.OP_READ);
        new Thread(new NioClientHandler(selector)).start();

        /**
         * 向服务器端发送数据
         */
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextLine()) {
            String request = scanner.nextLine();
            if (request != null && request.length() > 0) {
                socketChannel.write(
                        Charset.forName("UTF-8")
                                .encode(nickname + " : " + request));
            }
        }

    }

补充循环接受服务器端消息的线程

**
 * 客户端线程类，专门接收服务器端响应信息
 */
public class NioClientHandler implements Runnable {
    private Selector selector;

    public NioClientHandler(Selector selector) {
        this.selector = selector;
    }

    @Override
    public void run() {

        try {
            for (;;) {
                int readyChannels = selector.select();

                if (readyChannels == 0) continue;

                /**
                 * 获取可用channel的集合
                 */
                Set<SelectionKey> selectionKeys = selector.selectedKeys();

                Iterator iterator = selectionKeys.iterator();

                while (iterator.hasNext()) {
                    /**
                     * selectionKey实例
                     */
                    SelectionKey selectionKey = (SelectionKey) iterator.next();

                    /**
                     * **移除Set中的当前selectionKey**
                     */
                    iterator.remove();

                    /**
                     * 7. 根据就绪状态，调用对应方法处理业务逻辑
                     */

                    /**
                     * 如果是 可读事件
                     */
                    if (selectionKey.isReadable()) {
                        readHandler(selectionKey, selector);
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 可读事件处理器
     */
    private void readHandler(SelectionKey selectionKey, Selector selector)
            throws IOException {
        /**
         * 要从 selectionKey 中获取到已经就绪的channel
         */
        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();

        /**
         * 创建buffer
         */
        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

        /**
         * 循环读取服务器端响应信息
         */
        String response = "";
        while (socketChannel.read(byteBuffer) > 0) {
            /**
             * 切换buffer为读模式
             */
            byteBuffer.flip();

            /**
             * 读取buffer中的内容
             */
            response += Charset.forName("UTF-8").decode(byteBuffer);
        }

        /**
         * 将channel再次注册到selector上，监听他的可读事件
         */
        socketChannel.register(selector, SelectionKey.OP_READ);

        /**
         * 将服务器端响应信息打印到本地
         */
        if (response.length() > 0) {
            System.out.println(response);
        }
    }
}

课程收获：
  通过对实战课的学习，对NIO的基本调用实现已经有了基本的了解。后续将根据工作中的场景看下是否进行应用