如何写“按下回车键”流？

发布于 2024-10-16 14:23:42 字数 1041 浏览 2 评论 0原文

抱歉这个听起来很奇怪的标题...

我有以下情况：我希望我的 Java 程序与外部控制台交互。为了将各个命令“发送”到该控制台，我需要模拟普通控制台上的“按下输入键”。为了澄清我想要什么，假设 mysql 没有其他 API，我需要通过控制台进行交互。虽然这不是我的实际问题，但它已经足够接近了。

我有以下代码：

        String command = "/usr/local/mysql/bin/mysql";
        Process child = Runtime.getRuntime().exec(command);

        StreamGobbler gobbler = new StreamGobbler(child.getInputStream());
        gobbler.start();

        BufferedWriter out = new BufferedWriter(new OutputStreamWriter(child.getOutputStream()));
        out.write("help");
        // here enter key needs to be pressed
        out.flush();
        // out.close();

如果执行了对 out.close() 的调用，则一切正常。但当然，这样我只能发送单个命令，这不是我想要的。但如果省略out.close()，则另一个程序永远不会执行该命令。我的猜测是它仍然等待命令“完成”，在普通控制台上可以通过按 Enter 来完成。 out.write(System.getProperty("line.separator")); 和 out.newLine(); （相同）并没有解决问题，也没有out.write("\r\n"); 和 out.write((char) 26); (EOF)。

当然，也可能是我做的完全错误（即错误的方法）。然后我将不胜感激指向正确方向的指针...

对此的任何帮助都非常感谢。

原文

Sorry for this odd-sounding title...

I have the following situation: I want my Java program to interact with an external console. In order to "send" the individual commands to that console, I need to simulate what would be an "enter key pressed" on a normal console. To clarify what I want, imagine mysql had no other API and I would need to interact via console. Although this is not my actual problem, it is close enough.

I have the following code:

        String command = "/usr/local/mysql/bin/mysql";
        Process child = Runtime.getRuntime().exec(command);

        StreamGobbler gobbler = new StreamGobbler(child.getInputStream());
        gobbler.start();

        BufferedWriter out = new BufferedWriter(new OutputStreamWriter(child.getOutputStream()));
        out.write("help");
        // here enter key needs to be pressed
        out.flush();
        // out.close();

If the call to out.close() is executed, everything is fine. But of course, this way I can only send a single command, which is not what I want. But if out.close() is omitted, the other program never executes the command. My guess is that it still waits for the command to "finish", which on a normal console would be done by pressing enter. out.write(System.getProperty("line.separator")); and out.newLine(); (which are the same) do not solve the problem, neither does out.write("\r\n"); and out.write((char) 26); (EOF).

Of course, it might be, that I am doing it completely wrong (i.e., wrong approach). Then I would appreciate a pointer into the right direction...

Any help on this highly appreciated.

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淡水深流 2024-10-23 14:23:42

以下代码在使用 Java 1.6.0_23 的 Windows 7 和使用 Java 1.6.0_22 的 Ubuntu 8.04 上运行良好：

public class Laj {

  private static class ReadingThread extends Thread {
    private final InputStream inputStream;
    private final String name;

    public ReadingThread(InputStream inputStream, String name) {
      this.inputStream = inputStream;
      this.name = name;
    }

    public void run() {
      try {
        BufferedReader in = new BufferedReader(
            new InputStreamReader(inputStream));
        for (String s = in.readLine(); s != null; s = in.readLine()) {
          System.console().writer().println(name + ": " + s);
        }
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }

  public static void main(String[] args) throws Exception {
    String command = "psql -U archadm arch";
    final Process child = Runtime.getRuntime().exec(command);
    new ReadingThread(child.getInputStream(), "out").start();
    new ReadingThread(child.getErrorStream(), "err").start();
    BufferedWriter out = new BufferedWriter(
        new OutputStreamWriter(child.getOutputStream()));
    out.write("\\h");
    out.newLine();
    out.flush();
    out.write("\\q");
    out.newLine();
    out.flush();
  }

}

newLine() 与编写平台行分隔符相同。正如人们所期望的那样，它打印出前面带有“out:”的帮助，然后退出。如果我不发送“\q”，它不会退出（显然）但仍然打印帮助。使用“\r\n”或“\r”而不是平台行分隔符对我来说看起来不是一个好主意，因为此类命令行实用程序通常会检测到它们没有从终端获取输入并假设它采用本机文本格式（认为“psql < script.sql”）。好的软件应该正确检测并接受所有合理的行结尾。

The following code works fine on both Windows 7 using Java 1.6.0_23 and on Ubuntu 8.04 using Java 1.6.0_22:

public class Laj {

  private static class ReadingThread extends Thread {
    private final InputStream inputStream;
    private final String name;

    public ReadingThread(InputStream inputStream, String name) {
      this.inputStream = inputStream;
      this.name = name;
    }

    public void run() {
      try {
        BufferedReader in = new BufferedReader(
            new InputStreamReader(inputStream));
        for (String s = in.readLine(); s != null; s = in.readLine()) {
          System.console().writer().println(name + ": " + s);
        }
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
  }

  public static void main(String[] args) throws Exception {
    String command = "psql -U archadm arch";
    final Process child = Runtime.getRuntime().exec(command);
    new ReadingThread(child.getInputStream(), "out").start();
    new ReadingThread(child.getErrorStream(), "err").start();
    BufferedWriter out = new BufferedWriter(
        new OutputStreamWriter(child.getOutputStream()));
    out.write("\\h");
    out.newLine();
    out.flush();
    out.write("\\q");
    out.newLine();
    out.flush();
  }

}

newLine() is the same as writing the platform line separator. As one would expect, it prints help preceded with "out: ", then exits. If I don't send "\q", it doesn't exit (obviously) but still prints help. Using "\r\n" or "\r" instead of the platform line separator doesn't look like a good idea to me, because such command-line utilities will usually detect that they don't get input from the terminal and assume it is in the native text format (think "psql < script.sql"). Good software should properly detect and accept all reasonable line endings though.

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