ProcessBuilder：转发stdout和stderr启动进程而不阻塞主线程

问题描述：

我正在使用ProcessBuilder在Java中构建一个进程，如下所示：

I'm building a process in Java using ProcessBuilder as follows:

ProcessBuilder pb = new ProcessBuilder()
        .command("somecommand", "arg1", "arg2")
        .redirectErrorStream(true);
Process p = pb.start();

InputStream stdOut = p.getInputStream();

现在我的问题如下：我想捕获通过stdout和/或stderr的任何内容该进程并将其重定向到 System.out 异步。我希望进程及其输出重定向在后台运行。到目前为止，我发现这样做的唯一方法是手动生成一个新的线程，该线程将连续读取 stdOut ，然后调用相应的 write（） System.out 的方法。

Now my problem is the following: I would like to capture whatever is going through stdout and/or stderr of that process and redirect it to System.out asynchronously. I want the process and its output redirection to run in the background. So far, the only way I've found to do this is to manually spawn a new thread that will continuously read from stdOut and then call the appropriate write() method of System.out.

new Thread(new Runnable(){
    public void run(){
        byte[] buffer = new byte[8192];
        int len = -1;
        while((len = stdOut.read(buffer)) > 0){
            System.out.write(buffer, 0, len);
        }
    }
}).start();

虽然这种方法很有效，但感觉有点脏。最重要的是，它为我提供了一个正确管理和终止的线程。有没有更好的方法呢？

While that approach kind of works, it feels a bit dirty. And on top of that, it gives me one more thread to manage and terminate correctly. Is there any better way to do this?

答

只能在 Java 6或更早版本中使用使用所谓的 StreamGobbler （您开始创建）：

To only way in Java 6 or earlier is with a so called StreamGobbler (which you are started to create):

StreamGobbler errorGobbler = new StreamGobbler(p.getErrorStream(), "ERROR");

// any output?
StreamGobbler outputGobbler = new StreamGobbler(p.getInputStream(), "OUTPUT");

// start gobblers
outputGobbler.start();
errorGobbler.start();

...

private class StreamGobbler extends Thread {
    InputStream is;
    String type;

    private StreamGobbler(InputStream is, String type) {
        this.is = is;
        this.type = type;
    }

    @Override
    public void run() {
        try {
            InputStreamReader isr = new InputStreamReader(is);
            BufferedReader br = new BufferedReader(isr);
            String line = null;
            while ((line = br.readLine()) != null)
                System.out.println(type + "> " + line);
        }
        catch (IOException ioe) {
            ioe.printStackTrace();
        }
    }
}

对于Java 7，请参阅Evgeniy Dorofeev的回答。

For Java 7, see Evgeniy Dorofeev's answer.

ProcessBuilder：转发stdout和stderr启动进程而不阻塞主线程

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