java如何改进从socket读取XML的方式

Question

我正在开发一个Java客户机，它通过socket连接到服务器并发送/接收XML消息。我知道消息的模式是什么。我目前正在使用它，但感觉很混乱，我还没有测试它，以了解它如何同时处理从服务器发送的多个XML

代码如下：

  private static BufferedReader socketIn;
  private static PrintWriter socketOut;
  private static final String SERVICES_FILE = "/etc/services";

  public static void main(String[] args) {
    int port = getServicePortByName("Service1", "tcp");
    try {
      logger.info("Creating socket port with ip: " + InetAddress.getLocalHost() + " and port: " + port);
      Socket socket = new Socket(InetAddress.getLocalHost(), port);
      socketOut = new PrintWriter(socket.getOutputStream(), true);

      String message = createMessageXML("LOGIN");
      socketOut.println(message);

      socketIn = new BufferedReader(new InputStreamReader(socket.getInputStream()));
      StringBuilder inputLine = new StringBuilder();
      String tmp;

      while (true) {
      //loop to keep listening/parsing
        while(socketIn.ready()) {
          tmp = socketIn.readLine();
          inputLine.append(tmp);
        }
        if(inputLine.length() > 0) {
          parseReceivedMessage(inputLine.toString());
        }
        inputLine.replace(0, inputLine.length(), "");
      }

    } catch (UnknownHostException ex) {
      Logger.getLogger(TestClient.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
      Logger.getLogger(TestClient.class.getName()).log(Level.SEVERE, null, ex);
    }
  }

parseReceivedMessage方法只接收字符串并将其转换为文档对象。我的问题是，有没有更好或更干净的方法来代替使用StringBuilder？我最初希望将InputStream传递给DOM builder解析方法。 我看到了一些使用ByteArray streams的示例，但我对这些有一些问题。如果需要澄清，请告诉我

Answer 1

我强烈建议您围绕XML消息设计一个框架协议。在每个XML消息前面加上一个长度值，该值指定要传输的字节数，然后发送XML本身（以字节为单位，而不是以字符为单位）。然后，接收方可以读取长度，然后读取指定数量的字节并将它们传递给XML解析器，然后读取下一个长度，依此类推。例如：

  private static DataInputStream socketIn;
  private static DataOutputStream socketOut;
  private static final String SERVICES_FILE = "/etc/services";

  public static void main(String[] args) {
    int port = getServicePortByName("Service1", "tcp");
    try {
      logger.info("Creating socket port with ip: " + InetAddress.getLocalHost() + " and port: " + port);
      Socket socket = new Socket(InetAddress.getLocalHost(), port);
      socketIn = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
      socketOut = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream()));

      byte[] message = createMessageXML("LOGIN");
      socketOut.writeInt(message.length());
      socketOut.write(message, 0, message.length());

      int len = socketIn.readInt();
      if (len > 0)
      {
          message = new byte[len];
          socketIn.readFully(message);
          parseReceivedMessage(message);
      }

    } catch (UnknownHostException ex) {
      Logger.getLogger(TestClient.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
      Logger.getLogger(TestClient.class.getName()).log(Level.SEVERE, null, ex);
    }
  }

Answer 2

ready()不是消息结尾的有效测试。去掉这个StringBuilder和readLine()调用，直接将输入流传递给DOM解析器