Java网络编程之NIO

public class EchoServer implements Runnable{
  private Selector selector;
  private ServerSocketChannel servChannel;
  private static int port = 8080;

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {

    EchoServer echoServer = new EchoServer();
    new Thread(echoServer, "NIO-EchoServer-001").start();
    }

    public EchoServer() {
    try {
      selector = Selector.open();
      servChannel = ServerSocketChannel.open();
      servChannel.configureBlocking(false);
      servChannel.socket().bind(new InetSocketAddress(port), 1024);
      servChannel.register(selector, SelectionKey.OP_ACCEPT);
    } catch (IOException e) {
      e.printStackTrace();
      System.exit(1);
    }
  }

  /**
   * 主函数
   */
  @Override
  public void run () {

    try {
      while (true) {
        try {
          selector.select(1000);
          Set<SelectionKey> selectedKeys = selector.selectedKeys();
          Iterator<SelectionKey> it = selectedKeys.iterator();
          SelectionKey key = null;
          while (it.hasNext()) {
            key = it.next();
            it.remove();
            try {
              handleInput(key);
            } catch (Exception e) {
              if (key != null) {
                key.cancel();
                if (key.channel() != null) {
                  key.channel().close();
                }
              }
            }
          }
        } catch (Throwable t) {
          t.printStackTrace();
        }
      }
    }finally {
      //关闭多路复用器，自动关闭其上的Channel
      if (selector != null) {
        try {
          selector.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }

  }

  /**
   * 处理请求
   * @param key
   * @throws IOException
   */
  private void handleInput(SelectionKey key) throws IOException {
    if (!key.isValid()) {
      return;
    }

    if (key.isAcceptable()) {
      ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
      SocketChannel sc = ssc.accept();
      sc.configureBlocking(false);
      //将新进来的连接加入到多路复用器，并监听读事件
      sc.register(selector, SelectionKey.OP_READ);
    }

    //读取消息，这个是前面Accept后的Socket
    if (key.isReadable()) {
      // Read the data
      SocketChannel sc = (SocketChannel) key.channel();
      //这里先写死1024字节，实际场景按需分配
      ByteBuffer readBuffer = ByteBuffer.allocate(1024);
      int readBytes = sc.read(readBuffer);
      if (readBytes > 0) {
        readBuffer.flip();
        byte[] bytes = new byte[readBuffer.remaining()];
        readBuffer.get(bytes);
        String body = new String(bytes, "UTF-8");
        doWrite(sc, body);
      } else if (readBytes < 0) {
        key.cancel();
        sc.close();
      } else {
        // 读到0字节，忽略
      }
    }

  }

  /**
   * 写入数据
   * @param channel
   * @param response
   * @throws IOException
   */
  private void doWrite(SocketChannel channel, String response) throws IOException {
    if (response != null && response.trim().length() > 0) {
      byte[] bytes = response.getBytes();
      ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
      writeBuffer.put(bytes);
      writeBuffer.flip();
      channel.write(writeBuffer);
    }
  }
}