NIO (New I/O)

/**
 * 
 * @author 闪电侠
 * @date 2019年2月21日
 * @Description: NIO 改造后的服务端
 */
public class NIOServer {
  public static void main(String[] args) throws IOException {
    // 1. serverSelector负责轮询是否有新的连接，服务端监测到新的连接之后，不再创建一个新的线程，
    // 而是直接将新连接绑定到clientSelector上，这样就不用 IO 模型中 1w 个 while 循环在死等
    Selector serverSelector = Selector.open();
    // 2. clientSelector负责轮询连接是否有数据可读
    Selector clientSelector = Selector.open();

    new Thread(() -> {
      try {
        // 对应IO编程中服务端启动
        ServerSocketChannel listenerChannel = ServerSocketChannel.open();
        listenerChannel.socket().bind(new InetSocketAddress(3333));
        listenerChannel.configureBlocking(false);
        listenerChannel.register(serverSelector, SelectionKey.OP_ACCEPT);

        while (true) {
          // 监测是否有新的连接，这里的1指的是阻塞的时间为 1ms
          if (serverSelector.select(1) > 0) {
            Set<SelectionKey> set = serverSelector.selectedKeys();
            Iterator<SelectionKey> keyIterator = set.iterator();

            while (keyIterator.hasNext()) {
              SelectionKey key = keyIterator.next();

              if (key.isAcceptable()) {
                try {
                  // (1) 每来一个新连接，不需要创建一个线程，而是直接注册到clientSelector
                  SocketChannel clientChannel = ((ServerSocketChannel) key.channel()).accept();
                  clientChannel.configureBlocking(false);
                  clientChannel.register(clientSelector, SelectionKey.OP_READ);
                } finally {
                  keyIterator.remove();
                }
              }

            }
          }
        }
      } catch (IOException ignored) {
      }
    }).start();
    new Thread(() -> {
      try {
        while (true) {
          // (2) 批量轮询是否有哪些连接有数据可读，这里的1指的是阻塞的时间为 1ms
          if (clientSelector.select(1) > 0) {
            Set<SelectionKey> set = clientSelector.selectedKeys();
            Iterator<SelectionKey> keyIterator = set.iterator();

            while (keyIterator.hasNext()) {
              SelectionKey key = keyIterator.next();

              if (key.isReadable()) {
                try {
                  SocketChannel clientChannel = (SocketChannel) key.channel();
                  ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
                  // (3) 面向 Buffer
                  clientChannel.read(byteBuffer);
                  byteBuffer.flip();
                  System.out.println(
                      Charset.defaultCharset().newDecoder().decode(byteBuffer).toString());
                } finally {
                  keyIterator.remove();
                  key.interestOps(SelectionKey.OP_READ);
                }
              }

            }
          }
        }
      } catch (IOException ignored) {
      }
    }).start();

  }
}