为Process.waitFor设置超时
2011-11-14 19:43 | dongliu84
| 标签:
java
Java中在使用Runtime.getRuntime().exec(command)调用系统命令后，一般会调用Process.waitFor()来等待命令执行结束，获取执行结果。今天一个悲剧的事实证明了，即使只是调用了很简单的脚本命令，在调用Process.waitFor()后同样可能发生无休止或者接近于无休止的阻塞。处理完故障之后痛定思痛，决定在代码中加入超时控制，但是Process.waitFor()本身并不支持超时时间设置。一个方法是改用非阻塞的Process.exitValue()方法，然后轮询检查进程状态，这种方式比较消耗CPU，以至于轮询间隔也不能设置得太小，总归不是很完美。另外就是多起一个线程，借助于其他的超时机制来控制。最后使用的代码如下：
public class ProcessUtils {
/**
* 运行一个外部命令，返回状态.若超过指定的超时时间，抛出TimeoutException
* @param command
* @param timeout
* @return
* @throws IOException
* @throws InterruptedException
* @throws TimeoutException
*/
public static int executeCommand(final String command, final long timeout) throws IOException, InterruptedException, TimeoutException {
Process process = Runtime.getRuntime().exec(command);
Worker worker = new Worker(process);
worker.start();
try {
worker.join(timeout);
if (worker.exit != null){
return worker.exit;
} else{
throw new TimeoutException();
}
} catch (InterruptedException ex) {
worker.interrupt();
Thread.currentThread().interrupt();
throw ex;
} finally {
process.destroy();
}
}
private static class Worker extends Thread {
private final Process process;
private Integer exit;
private Worker(Process process) {
this.process = process;
}
public void run() {
try {
exit = process.waitFor();
} catch (InterruptedException ignore) {
return;
}
}
}
}
/**
* 运行一个外部命令，返回状态.若超过指定的超时时间，抛出TimeoutException
* @param command
* @param timeout
* @return
* @throws IOException
* @throws InterruptedException
* @throws TimeoutException
*/
public static int executeCommand(final String command, final long timeout) throws IOException, InterruptedException, TimeoutException {
Process process = Runtime.getRuntime().exec(command);
Worker worker = new Worker(process);
worker.start();
try {
worker.join(timeout);
if (worker.exit != null){
return worker.exit;
} else{
throw new TimeoutException();
}
} catch (InterruptedException ex) {
worker.interrupt();
Thread.currentThread().interrupt();
throw ex;
} finally {
process.destroy();
}
}
private static class Worker extends Thread {
private final Process process;
private Integer exit;
private Worker(Process process) {
this.process = process;
}
public void run() {
try {
exit = process.waitFor();
} catch (InterruptedException ignore) {
return;
}
}
}
}
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