在 Windows 下，当我的程序从命令行启动时，我无法可靠地操作子进程的 I/O。令人沮丧的是，服务器使用控制台进行 I/O 是标准的。GUI 很好，但我真的更喜欢坚持使用命令行并保持简单。我注意到当我从 Eclipse IDE 执行服务器时，子进程 I/O 很好，但从命令行运行则完全不同。我无法读取或写入子进程，但该进程仍在运行。我在下面编写了一些测试代码来演示这个问题，我希望这个问题可以在另一台机器上重现，然后希望从中得到解决方案。从 Eclipse 执行时，继承的 I/O 会按预期工作。然而，当从 Windows 命令提示符执行时，没有任何内容可以读取或写入子进程。在这两种情况下，将子进程输出重定向到文件总是成功，但输入仍然无法传递给子进程。如果已经有解决此问题的方法，请链接该页面。
JRE/JDK 实现：
>java -version
java version "1.7.0_01"
Java(TM) SE Runtime Environment (build 1.7.0_01-b08)
Java HotSpot(TM) 64-Bit Server VM (build 21.1-b02, mixed mode)
考虑以下代码：
package com.comp8nerd4u2.io.test;
/*
* These tests attempt to confirm what I'm experiencing under my build environment
*/
import java.io.File;
import java.io.IOException;
public final class PIOTest {
/** The command to run as a child process. The command itself isn't the test, but what you use to run this Java program is the test. */
private static final String[] COMMAND = {"cmd.exe", "/c", "echo This is a test. Feel free to change this."}; // Change this to just {"cmd.exe"} or some other program that accepts input and you'll see how frustrating this is
/** Controls how the test process is built */
private static final ProcessBuilder PB = new ProcessBuilder(COMMAND);
/** How long to allow the process to run before forcibly terminating it. */
private static final long PROCESS_TIMEOUT = 10000L;
private static final Runnable R = new TimedInterruptWorker(PROCESS_TIMEOUT);
private static int n = 0;
static {
PB.redirectErrorStream(true);
}
private PIOTest() {}
public static void main(String[] args) {
// ----- Begin Tests -----
/*
* Test #1: Let's test putting our command's output onto our standard I/O streams
* Goal condition: Child process outputs expected output, and exits before the timeout. If child process expects input, it should accept entered input.
* Known success factors: Parent process' standard I/O is piped to Eclipse. Tests would probably succeed with Netbeans as well
* Known fail factors: Parent process' standard I/O is piped to Windows Command Prompt
* Result under fail condition: Child process hangs if it fills up its output buffer or requests input, but exits on its own otherwise, unless it took longer than the timeout.
*/
PB.inheritIO();
doTest();
// Test #2: Let's test putting our command's output into a file
PB.redirectOutput(new File("piotest.txt"));
doTest();
}
/**
* Performs the I/O test.
*/
private static void doTest() {
n++;
Process p = null;
try {
p = PB.start();
} catch (IOException e) {
e.printStackTrace();
return;
}
try {
Thread t = new Thread(R);
t.setDaemon(true);
t.start();
System.out.format("[Test #%d] Child exited with status code %d\n", n, p.waitFor());
t.interrupt();
} catch (InterruptedException e) {
p.destroy();
System.out.format("[Test #%d] Child took longer than the timeout.\n", n);
}
}
/**
* Useful for sending interrupts after a certain amount of time has passed.
*
* @author comp8nerd4u2
*/
private static final class TimedInterruptWorker implements Runnable {
private long timeout = 0;
private Thread target = null;
public TimedInterruptWorker(long timeout) {
this(timeout, Thread.currentThread());
}
public TimedInterruptWorker(long timeout, Thread target) {
this.timeout = timeout;
this.target = target;
}
@Override
public void run() {
try {
Thread.sleep(timeout);
} catch (InterruptedException e) {
return;
}
target.interrupt();
}
}
}
更新：我修改了测试以在运行时接受任何命令，并将其上传到我的 linux vps 服务器。我从 ssh 会话运行它，所有子进程的 I/O 都可以轻松读取和写入。我注意到了一件事。当我打开一个交互式 bash shell 作为子进程，然后将它的输出重定向到一个文件时，我想 CentOS 停止了我的程序。那或我的程序崩溃了。
[admin@comp8nerd4u2 piotest]$ java -jar piotest.jar
Enter command to run : bash
[admin@comp8nerd4u2 piotest]$ [Test #1] Child took longer than the timeout.
[1]+ Stopped java -jar piotest.jar
[admin@comp8nerd4u2 piotest]$
第一行是我输入的命令。第二行是生成的 bash shell，但我从未在其中输入任何内容，因此我的程序在超时后将其杀死。它为第二次测试做好准备，创建“piotest.txt”文件，然后崩溃或被操作系统停止。实际测试本身没有改变，只是测试现在允许您输入在运行时运行的命令。这在linux中可以正常工作，但在windows中不行。我希望知道 Win32 API 的人能以某种方式解释为什么这个测试在 Windows 中失败。