ScheduledExecutorService 只运行一次

Question

我想要一个进程运行在我启动我的网络服务之后，然后每隔 30 分钟左右，（我现在正在以较小的延迟测试它，只是为了看看它是否有效），但我的过程从未运行超过一次。我做错了什么？

这是我的代码：

@WebListener
public class SchedulerService implements ServletContextListener{

    @Autowired
    UpdateSubscriberService updateSubscriberService;

    ScheduledExecutorService scheduledExecService;

    public SchedulerService(){
        scheduledExecService = Executors.newSingleThreadScheduledExecutor();
    }

    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
        scheduledExecService.shutdown();
    }

    @Override
    public void contextInitialized(ServletContextEvent arg0) {
        scheduledExecService.scheduleWithFixedDelay(new Runnable(){
            @Override
            public void run() {
                Date date = new Date(System.currentTimeMillis());
                System.out.println("Running scheduled update check " + date.toString());
                updateSubscriberService.checkForUpdates();
            }
        }, 60, 30, TimeUnit.SECONDS);
    }
}

Answer 1

在类似问题上查看我的更长 Answer。

用 `try catch`

包装 run 代码

只是猜测：抛出异常。如果遇到异常，ScheduledExecutorService 将静默停止，不再执行计划的工作。

run 方法的代码应始终被 try-catch 包围，以处理和吸收任何抛出的异常。

 @Override
 public void run() {
    try {  // Let no Exception reach the ScheduledExecutorService.
        Date date = new Date(System.currentTimeMillis());
        System.out.println("Running scheduled update check " + date.toString());
        updateSubscriberService.checkForUpdates();
    } catch ( Exception e ) {
        System.out.println( "ERROR - unexpected exception" );
    }
}

剔除`run`方法

慢慢来。从 run 方法开始，该方法只执行 System.out.println.

Answer 2

以防万一您遇到代码必须每隔这么多秒运行一次的情况，即使最后一个运行尚未完成（这可能非常如果管理不当会很危险），您可以在计时器内的不同线程内启动您的进程。这是示例代码。

ScheduledExecutorService scheduledExecService = newSingleThreadScheduledExecutor();
scheduledExecService.scheduleWithFixedDelay(new Runnable()
{
    @Override
    public void run()
    {
        // This should be in a try-catch because any error here
        // will stop the recurrence
        try
        {
            // The timer will only repeat if the last run is finished. So
            // we put each new process in a different thread than the timer
            // itself, so the last timer call "finishes" as soon as the process
            // leaves the timer's thread.
            Thread t = new Thread(new Runnable()
            {
                public void run()
                {
                    try
                    {
                        android.os.Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
                        MyProcessThatShouldRunEverySoManySecondsNoMatterWhat();
                    }
                    catch (Exception erTimerThread)
                    {
                        Log.e("Error", erTimerThread.toString());
                    }
                }
            });
            t.setPriority(2);
            t.start();
        }
        catch (Exception erTimer)
        {
            Log.e("Error", erTimer.toString());
        }
    }
}, 0, 60, java.util.concurrent.TimeUnit.SECONDS);

ScheduledExecutorService 只运行一次

ScheduledExecutorService only runs once

java

spring

spring-mvc

scheduler

scheduled-tasks

用 `try catch`

剔除`run`方法

ScheduledExecutorService 只运行一次

ScheduledExecutorService only runs once

java

spring

spring-mvc

scheduler

scheduled-tasks

用 try catch

剔除run方法

用 `try catch`

剔除`run`方法