Java使用NioSocket手动实现HTTP服务器

public class HttpServer {
  public static void main(String[] args) throws Exception{
    ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
    serverSocketChannel.socket().bind(new InetSocketAddress((8080)));
    serverSocketChannel.configureBlocking(false);

    Selector selector = Selector.open();

    // It must be ACCEPT, or it will throw exception
    serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

    while(true){
      if (selector.select(3000) == 0){
        continue;
      }

      Iterator keyIter = selector.selectedKeys().iterator();

      while (keyIter.hasNext()){
        SelectionKey key = keyIter.next();
        new Thread(new HttpHandler(key)).run();
        keyIter.remove();
      }
    }
  }
}

class HttpHandler implements Runnable{
  private int bufferSize = 1024;
  private String localCharset = "UTF-8";
  private SelectionKey key;

  public HttpHandler(SelectionKey key){
    this.key = key;
  }

  public void handleAccept() throws IOException{}

  public void handleRead() throws IOException{}

  @Override
  public void run() {
    try {
      if(key.isAcceptable()){
        handleAccept();
      }
      if(key.isReadable()){
        handleRead();
      }
    }catch (IOException ex){
      ex.printStackTrace();
    }
  }
}

  public void handleAccept() throws IOException{
    SocketChannel clientChannel =
        ((ServerSocketChannel)key.channel()).accept();
    clientChannel.configureBlocking(false);
    clientChannel.register(
        key.selector(), SelectionKey.OP_READ, ByteBuffer.allocate(bufferSize)
      );
  }

  public void handleRead() throws IOException{
    SocketChannel sc = (SocketChannel)key.channel();
    ByteBuffer buffer = (ByteBuffer)key.attachment();
    buffer.clear();

    if (sc.read(buffer) == -1){
      sc.close();
    }else {
      buffer.flip();
      String receiveString = Charset.forName(localCharset).newDecoder().decode(buffer).toString();

      String[] requestMessage = receiveString.split("\r\n");
      for (String s: requestMessage){
        System.out.println(s);
        if (s.isEmpty()){
          break;
        }
      }

      String[] firstLine = requestMessage[0].split(" ");
      System.out.println();
      System.out.println("Method:\t"+ firstLine[0]);
      System.out.println("url:\t"+firstLine[1]);
      System.out.println("HTTP Version:\t" + firstLine[2]);
      System.out.println();

      StringBuilder sendString = new StringBuilder();
      sendString.append("HTTP/1.1 200 OK\r\n");
      sendString.append("Content-Type:text/html;Charset="+localCharset+"\r\n");
      sendString.append("\r\n");
      sendString.append("");
      sendString.append("Received:
");

      for (String s : requestMessage){
        sendString.append(s + "
");
      }
      sendString.append("");
      buffer = ByteBuffer.wrap(sendString.toString().getBytes(localCharset));
      sc.write(buffer);
      sc.close();
    }
  }