如何在Java中处理多个流？ [英] How do I handle multiple streams in Java?

问题描述

我正在尝试运行一个进程，并对其输入，输出和错误流进行处理。显而易见的方法是使用类似 select（）的东西，但我在Java中唯一可以找到的就是 Selector.select （），它需要频道。似乎无法从 InputStream 或 OutputStream <获取频道 / code>（ FileStream 有一个 getChannel（）方法，但这对此没有帮助）

I'm trying to run a process and do stuff with its input, output and error streams. The obvious way to do this is to use something like select(), but the only thing I can find in Java that does that is Selector.select(), which takes a Channel. It doesn't appear to be possible to get a Channel from an InputStream or OutputStream (FileStream has a getChannel() method but that doesn't help here)

所以，我编写了一些代码来轮询所有流：

So, instead I wrote some code to poll all the streams:

while( !out_eof || !err_eof )
{
    while( out_str.available() )
    {
        if( (bytes = out_str.read(buf)) != -1 )
        {
            // Do something with output stream
        }
        else
            out_eof = true;
    }
    while( err_str.available() )
    {
        if( (bytes = err_str.read(buf)) != -1 )
        {
            // Do something with error stream
        }
        else
            err_eof = true;
    }
    sleep(100);
}

有效，但它永远不会终止。当其中一个流到达文件末尾时， available（）返回零，因此 read（）未被调用我们永远不会得到表示EOF的-1返回。

which works, except that it never terminates. When one of the streams reaches end of file, available() returns zero so read() isn't called and we never get the -1 return that would indicate EOF.

一种解决方案是检测EOF的非阻塞方式。我无法在任何地方看到文档中的一个。或者有更好的方法来做我想做的事情吗？

One solution would be a non-blocking way to detect EOF. I can't see one in the docs anywhere. Alternatively is there a better way of doing what I want to do?

我在这里看到这个问题：
链接文本
虽然它并不完全按照我的意愿行事，但我可能会使用这个想法，为每个流产生单独的线程，以解决我现在遇到的特殊问题。但当然这不是唯一的方法吗？当然必须有一种方法可以从多个流中读取而不使用每个线程？

I see this question here: link text and although it doesn't exactly do what I want, I can probably use that idea, of spawning separate threads for each stream, for the particular problem I have now. But surely that isn't the only way to do it? Surely there must be a way to read from multiple streams without using a thread for each?

推荐答案

如你所说，解决方案<本答案中概述的href =https://stackoverflow.com/questions/60302/starting-a-process-with-inherited-stdinstdoutstderr-in-java-6#60578是传统的方式从进程中读取stdout和stderr。每个流的线程是可行的，即使它有点烦人。

As you said, the solution outlined in this Answer is the traditional way of reading both stdout and stderr from a Process. A thread-per-stream is the way to go, even though it is slightly annoying.

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