Question

我有一个写入数据库的方法。要求是确保在经过一段时间后该方法不会执行。如果它在此之前返回，则不应该做任何事情。

我能想到的一个基本方法是做这样的事情。

public class LimitedRuntime {

    public static void writeToDb(){
            // writes to the database
    }

    public static void main(String[] args) {
        long totalExecutionTime = 8000L;
        long startTime = System.currentTimeMillis();

        while(System.currentTimeMillis() - startTime < totalExecutionTime )
        {
            writeToDb();
        }   
    }
}

这种方法的一个问题是，即使方法在最大总执行时间之前返回，即使这样，程序也会停止以等待时间过去。

我怎样才能做得更好（或者更正确）？如果我们使用Thread，我们如何找出哪个Thread执行该方法？

Answer 1

您可以通过将您的工作发送给遗嘱执行人来完成此任务：

 public static void main(String[] args) {
    ExecutorService executor = Executors.newFixedThreadPool(4);

    Future<?> future = executor.submit(new Runnable() {
        @Override
        public void run() {
            writeToDb();            //        <-- your job
        }
    });

    executor.shutdown();            //        <-- reject all further submissions

    try {
        future.get(8, TimeUnit.SECONDS);  //     <-- wait 8 seconds to finish
    } catch (InterruptedException e) {    //     <-- possible error cases
        System.out.println("job was interrupted");
    } catch (ExecutionException e) {
        System.out.println("caught exception: " + e.getCause());
    } catch (TimeoutException e) {
        future.cancel(true);              //     <-- interrupt the job
        System.out.println("timeout");
    }

    // wait all unfinished tasks for 2 sec
    if(!executor.awaitTermination(2, TimeUnit.SECONDS)){
        // force them to quit by interrupting
        executor.shutdownNow();
    }
}

Answer 2

There is also an AspectJ solution for that with jcabi-aspects library:

@Timeable(limit = 5, unit = TimeUnit.SECONDS)
public String writeToDb() {
  // writeToDb
}

There is an article explaining it further: Limit Java Method Execution Time

设置方法/线程的最大执行时间

2 个答案: