java - 如何使用 ScheduledExecutorService 每天在特定时间运行特定任务？

Question

我每天早上 5 点尝试执行某项任务。所以我决定使用ScheduledExecutorService它，但到目前为止，我已经看到了一些示例，这些示例展示了如何每隔几分钟运行一次任务。

而且我找不到任何示例来说明如何在每天早上的特定时间（5 AM）运行任务，并且还考虑到夏令时的事实 -

下面是我的代码，它将每 15 分钟运行一次 -

public class ScheduledTaskExample {
    private final ScheduledExecutorService scheduler = Executors
        .newScheduledThreadPool(1);

    public void startScheduleTask() {
    /**
    * not using the taskHandle returned here, but it can be used to cancel
    * the task, or check if it's done (for recurring tasks, that's not
    * going to be very useful)
    */
    final ScheduledFuture<?> taskHandle = scheduler.scheduleAtFixedRate(
        new Runnable() {
            public void run() {
                try {
                    getDataFromDatabase();
                }catch(Exception ex) {
                    ex.printStackTrace(); //or loggger would be better
                }
            }
        }, 0, 15, TimeUnit.MINUTES);
    }

    private void getDataFromDatabase() {
        System.out.println("getting data...");
    }

    public static void main(String[] args) {
        ScheduledTaskExample ste = new ScheduledTaskExample();
        ste.startScheduleTask();
    }
}

ScheduledExecutorService有什么办法，考虑到夏令时的事实，我可以安排一个任务在每天早上 5 点运行吗？

并且TimerTask对此或更好ScheduledExecutorService？

score 123 · Accepted Answer

与当前的 java SE 8 版本一样，它具有出色的日期时间 API，java.time可以更轻松地完成此类计算，而不是使用 java.util.Calendarand java.util.Date。

使用这个新 API的日期时间类，即 LocalDateTime
使用ZonedDateTime类来处理时区特定的计算，包括夏令时问题。您将在此处找到教程和示例。

现在作为使用您的用例安排任务的示例示例：

ZonedDateTime now = ZonedDateTime.now(ZoneId.of("America/Los_Angeles"));
ZonedDateTime nextRun = now.withHour(5).withMinute(0).withSecond(0);
if(now.compareTo(nextRun) > 0)
    nextRun = nextRun.plusDays(1);

Duration duration = Duration.between(now, nextRun);
long initialDelay = duration.getSeconds();

ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);            
scheduler.scheduleAtFixedRate(new MyRunnableTask(),
    initialDelay,
    TimeUnit.DAYS.toSeconds(1),
    TimeUnit.SECONDS);

计算initialDelay以要求调度程序延迟执行TimeUnit.SECONDS。对于此用例，单位毫秒及以下的时差问题似乎可以忽略不计。但是您仍然可以使用duration.toMillis()和TimeUnit.MILLISECONDS处理以毫秒为单位的调度计算。

而且 TimerTask 更适合这个或 ScheduledExecutorService？

NO： ScheduledExecutorService貌似比TimerTask. StackOverflow 已经为您提供了答案。

来自@PaddyD，

如果您希望它在正确的本地时间运行，您仍然需要每年重新启动两次。除非您对全年相同的 UTC 时间感到满意，否则 scheduleAtFixedRate 不会削减它。

确实如此，@PaddyD 已经给出了解决方法（给他+1），我提供了一个带有 Java8 日期时间 API 的工作示例ScheduledExecutorService。使用守护线程是危险的

class MyTaskExecutor
{
    ScheduledExecutorService executorService = Executors.newScheduledThreadPool(1);
    MyTask myTask;
    volatile boolean isStopIssued;

    public MyTaskExecutor(MyTask myTask$) 
    {
        myTask = myTask$;
        
    }
    
    public void startExecutionAt(int targetHour, int targetMin, int targetSec)
    {
        Runnable taskWrapper = new Runnable(){

            @Override
            public void run() 
            {
                myTask.execute();
                startExecutionAt(targetHour, targetMin, targetSec);
            }
            
        };
        long delay = computeNextDelay(targetHour, targetMin, targetSec);
        executorService.schedule(taskWrapper, delay, TimeUnit.SECONDS);
    }

    private long computeNextDelay(int targetHour, int targetMin, int targetSec) 
    {
        LocalDateTime localNow = LocalDateTime.now();
        ZoneId currentZone = ZoneId.systemDefault();
        ZonedDateTime zonedNow = ZonedDateTime.of(localNow, currentZone);
        ZonedDateTime zonedNextTarget = zonedNow.withHour(targetHour).withMinute(targetMin).withSecond(targetSec);
        if(zonedNow.compareTo(zonedNextTarget) > 0)
            zonedNextTarget = zonedNextTarget.plusDays(1);
        
        Duration duration = Duration.between(zonedNow, zonedNextTarget);
        return duration.getSeconds();
    }
    
    public void stop()
    {
        executorService.shutdown();
        try {
            executorService.awaitTermination(1, TimeUnit.DAYS);
        } catch (InterruptedException ex) {
            Logger.getLogger(MyTaskExecutor.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

笔记：

MyTask是一个带有函数的接口execute。
停止ScheduledExecutorService时，总是awaitTermination在调用shutdown它之后使用：你的任务总是有可能卡住/死锁，用户会永远等待。

我之前用 Calender 给出的例子只是我提到的一个想法，我避免了精确的时间计算和夏令时问题。根据@PaddyD 的抱怨更新了解决方案

score 27 · Accepted Answer

在 Java 8 中：

scheduler = Executors.newScheduledThreadPool(1);

//Change here for the hour you want ----------------------------------.at()       
Long midnight=LocalDateTime.now().until(LocalDate.now().plusDays(1).atStartOfDay(), ChronoUnit.MINUTES);
scheduler.scheduleAtFixedRate(this, midnight, 1440, TimeUnit.MINUTES);

score 7 · Accepted Answer

如果您没有能够使用 Java 8 的奢侈，以下将满足您的需要：

public class DailyRunnerDaemon
{
   private final Runnable dailyTask;
   private final int hour;
   private final int minute;
   private final int second;
   private final String runThreadName;

   public DailyRunnerDaemon(Calendar timeOfDay, Runnable dailyTask, String runThreadName)
   {
      this.dailyTask = dailyTask;
      this.hour = timeOfDay.get(Calendar.HOUR_OF_DAY);
      this.minute = timeOfDay.get(Calendar.MINUTE);
      this.second = timeOfDay.get(Calendar.SECOND);
      this.runThreadName = runThreadName;
   }

   public void start()
   {
      startTimer();
   }

   private void startTimer();
   {
      new Timer(runThreadName, true).schedule(new TimerTask()
      {
         @Override
         public void run()
         {
            dailyTask.run();
            startTimer();
         }
      }, getNextRunTime());
   }


   private Date getNextRunTime()
   {
      Calendar startTime = Calendar.getInstance();
      Calendar now = Calendar.getInstance();
      startTime.set(Calendar.HOUR_OF_DAY, hour);
      startTime.set(Calendar.MINUTE, minute);
      startTime.set(Calendar.SECOND, second);
      startTime.set(Calendar.MILLISECOND, 0);

      if(startTime.before(now) || startTime.equals(now))
      {
         startTime.add(Calendar.DATE, 1);
      }

      return startTime.getTime();
   }
}

它不需要任何外部库，并且会考虑夏令时。只需传入您想要将任务作为Calendar对象运行的时间，并将任务作为Runnable. 例如：

Calendar timeOfDay = Calendar.getInstance();
timeOfDay.set(Calendar.HOUR_OF_DAY, 5);
timeOfDay.set(Calendar.MINUTE, 0);
timeOfDay.set(Calendar.SECOND, 0);

new DailyRunnerDaemon(timeOfDay, new Runnable()
{
   @Override
   public void run()
   {
      try
      {
        // call whatever your daily task is here
        doHousekeeping();
      }
      catch(Exception e)
      {
        logger.error("An error occurred performing daily housekeeping", e);
      }
   }
}, "daily-housekeeping");

注意计时器任务在不建议执行任何 IO 的守护线程中运行。如果您需要使用用户线程，则需要添加另一个取消计时器的方法。

如果必须使用 a ScheduledExecutorService，只需将startTimer方法更改为以下内容：

private void startTimer()
{
   Executors.newSingleThreadExecutor().schedule(new Runnable()
   {
      Thread.currentThread().setName(runThreadName);
      dailyTask.run();
      startTimer();
   }, getNextRunTime().getTime() - System.currentTimeMillis(),
   TimeUnit.MILLISECONDS);
}

我不确定这种行为，但您可能需要一个 stop 方法，shutdownNow如果您沿着ScheduledExecutorService路线走，该方法会调用，否则当您尝试停止应用程序时，您的应用程序可能会挂起。

score 6 · Accepted Answer

您是否考虑过使用Quartz Scheduler 之类的东西？这个库有一种机制，可以使用类似 cron 的表达式来安排任务在每天设定的时间段内运行（看看CronScheduleBuilder）。

一些示例代码（未测试）：

public class GetDatabaseJob implements InterruptableJob
{
    public void execute(JobExecutionContext arg0) throws JobExecutionException
    {
        getFromDatabase();
    }
}

public class Example
{
    public static void main(String[] args)
    {
        JobDetails job = JobBuilder.newJob(GetDatabaseJob.class);

        // Schedule to run at 5 AM every day
        ScheduleBuilder scheduleBuilder = 
                CronScheduleBuilder.cronSchedule("0 0 5 * * ?");
        Trigger trigger = TriggerBuilder.newTrigger().
                withSchedule(scheduleBuilder).build();

        Scheduler scheduler = StdSchedulerFactory.getDefaultScheduler();
        scheduler.scheduleJob(job, trigger);

        scheduler.start();
    }
}

前面还有一些工作要做，你可能需要重写你的作业执行代码，但它应该让你更好地控制你希望你的作业如何运行。此外，如果您需要，更改时间表会更容易。

score 6 · Accepted Answer

Java8：
我的最佳答案升级版本：

修复了 Web Application Server 不想停止的情况，因为线程池有空闲线程
没有递归
使用您的自定义当地时间运行任务，在我的情况下，它是白俄罗斯，明斯克

/**
 * Execute {@link AppWork} once per day.
 * <p>
 * Created by aalexeenka on 29.12.2016.
 */
public class OncePerDayAppWorkExecutor {

    private static final Logger LOG = AppLoggerFactory.getScheduleLog(OncePerDayAppWorkExecutor.class);

    private ScheduledExecutorService executorService = Executors.newScheduledThreadPool(1);

    private final String name;
    private final AppWork appWork;

    private final int targetHour;
    private final int targetMin;
    private final int targetSec;

    private volatile boolean isBusy = false;
    private volatile ScheduledFuture<?> scheduledTask = null;

    private AtomicInteger completedTasks = new AtomicInteger(0);

    public OncePerDayAppWorkExecutor(
            String name,
            AppWork appWork,
            int targetHour,
            int targetMin,
            int targetSec
    ) {
        this.name = "Executor [" + name + "]";
        this.appWork = appWork;

        this.targetHour = targetHour;
        this.targetMin = targetMin;
        this.targetSec = targetSec;
    }

    public void start() {
        scheduleNextTask(doTaskWork());
    }

    private Runnable doTaskWork() {
        return () -> {
            LOG.info(name + " [" + completedTasks.get() + "] start: " + minskDateTime());
            try {
                isBusy = true;
                appWork.doWork();
                LOG.info(name + " finish work in " + minskDateTime());
            } catch (Exception ex) {
                LOG.error(name + " throw exception in " + minskDateTime(), ex);
            } finally {
                isBusy = false;
            }
            scheduleNextTask(doTaskWork());
            LOG.info(name + " [" + completedTasks.get() + "] finish: " + minskDateTime());
            LOG.info(name + " completed tasks: " + completedTasks.incrementAndGet());
        };
    }

    private void scheduleNextTask(Runnable task) {
        LOG.info(name + " make schedule in " + minskDateTime());
        long delay = computeNextDelay(targetHour, targetMin, targetSec);
        LOG.info(name + " has delay in " + delay);
        scheduledTask = executorService.schedule(task, delay, TimeUnit.SECONDS);
    }

    private static long computeNextDelay(int targetHour, int targetMin, int targetSec) {
        ZonedDateTime zonedNow = minskDateTime();
        ZonedDateTime zonedNextTarget = zonedNow.withHour(targetHour).withMinute(targetMin).withSecond(targetSec).withNano(0);

        if (zonedNow.compareTo(zonedNextTarget) > 0) {
            zonedNextTarget = zonedNextTarget.plusDays(1);
        }

        Duration duration = Duration.between(zonedNow, zonedNextTarget);
        return duration.getSeconds();
    }

    public static ZonedDateTime minskDateTime() {
        return ZonedDateTime.now(ZoneId.of("Europe/Minsk"));
    }

    public void stop() {
        LOG.info(name + " is stopping.");
        if (scheduledTask != null) {
            scheduledTask.cancel(false);
        }
        executorService.shutdown();
        LOG.info(name + " stopped.");
        try {
            LOG.info(name + " awaitTermination, start: isBusy [ " + isBusy + "]");
            // wait one minute to termination if busy
            if (isBusy) {
                executorService.awaitTermination(1, TimeUnit.MINUTES);
            }
        } catch (InterruptedException ex) {
            LOG.error(name + " awaitTermination exception", ex);
        } finally {
            LOG.info(name + " awaitTermination, finish");
        }
    }

}

score 2 · Accepted Answer

我有一个类似的问题。我不得不使用ScheduledExecutorService. 这通过从凌晨 3:30 开始的一项任务来解决，该任务相对于他当前的时间安排所有其他任务。并重新安排第二天凌晨 3 点 30 分。

在这种情况下，夏令时不再是问题。

score 2 · Accepted Answer

您可以使用简单的日期解析，如果一天中的时间在现在之前，让我们从明天开始：

  String timeToStart = "12:17:30";
  SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd 'at' HH:mm:ss");
  SimpleDateFormat formatOnlyDay = new SimpleDateFormat("yyyy-MM-dd");
  Date now = new Date();
  Date dateToStart = format.parse(formatOnlyDay.format(now) + " at " + timeToStart);
  long diff = dateToStart.getTime() - now.getTime();
  if (diff < 0) {
    // tomorrow
    Date tomorrow = new Date();
    Calendar c = Calendar.getInstance();
    c.setTime(tomorrow);
    c.add(Calendar.DATE, 1);
    tomorrow = c.getTime();
    dateToStart = format.parse(formatOnlyDay.format(tomorrow) + " at " + timeToStart);
    diff = dateToStart.getTime() - now.getTime();
  }

  ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);            
  scheduler.scheduleAtFixedRate(new MyRunnableTask(), TimeUnit.MILLISECONDS.toSeconds(diff) ,
                                  24*60*60, TimeUnit.SECONDS);

score 2 · Accepted Answer

如果您的服务器在凌晨 4:59 出现故障并在凌晨 5:01 恢复，该怎么办？我认为它只会跳过运行。我会推荐像 Quartz 这样的持久调度器，它将其调度数据存储在某个地方。然后它将看到此运行尚未执行，并将在上午 5:01 执行。

score 1 · Accepted Answer

您可以使用以下课程来安排您每天特定时间的任务

package interfaces;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;
import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class CronDemo implements Runnable{

    public static void main(String[] args) {

        Long delayTime;

        ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);

        final Long initialDelay = LocalDateTime.now().until(LocalDate.now().plusDays(1).atTime(12, 30), ChronoUnit.MINUTES);

        if (initialDelay > TimeUnit.DAYS.toMinutes(1)) {
            delayTime = LocalDateTime.now().until(LocalDate.now().atTime(12, 30), ChronoUnit.MINUTES);
        } else {
            delayTime = initialDelay;
        }

        scheduler.scheduleAtFixedRate(new CronDemo(), delayTime, TimeUnit.DAYS.toMinutes(1), TimeUnit.MINUTES);

    }

    @Override
    public void run() {
        System.out.println("I am your job executin at:" + new Date());
    }
}

score 1 · Accepted Answer

Just to add up on Victor's answer.

I would recommend to add a check to see, if the variable (in his case the long midnight) is higher than 1440. If it is, I would omit the .plusDays(1), otherwise the task will only run the day after tomorrow.

I did it simply like this:

Long time;

final Long tempTime = LocalDateTime.now().until(LocalDate.now().plusDays(1).atTime(7, 0), ChronoUnit.MINUTES);
if (tempTime > 1440) {
    time = LocalDateTime.now().until(LocalDate.now().atTime(7, 0), ChronoUnit.MINUTES);
} else {
    time = tempTime;
}

score 1 · Accepted Answer

以下示例对我有用

public class DemoScheduler {

    public static void main(String[] args) {

        // Create a calendar instance
        Calendar calendar = Calendar.getInstance();

        // Set time of execution. Here, we have to run every day 4:20 PM; so,
        // setting all parameters.
        calendar.set(Calendar.HOUR, 8);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.AM_PM, Calendar.AM);

        Long currentTime = new Date().getTime();

        // Check if current time is greater than our calendar's time. If So,
        // then change date to one day plus. As the time already pass for
        // execution.
        if (calendar.getTime().getTime() < currentTime) {
            calendar.add(Calendar.DATE, 1);
        }

        // Calendar is scheduled for future; so, it's time is higher than
        // current time.
        long startScheduler = calendar.getTime().getTime() - currentTime;

        // Setting stop scheduler at 4:21 PM. Over here, we are using current
        // calendar's object; so, date and AM_PM is not needed to set
        calendar.set(Calendar.HOUR, 5);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.AM_PM, Calendar.PM);

        // Calculation stop scheduler
        long stopScheduler = calendar.getTime().getTime() - currentTime;

        // Executor is Runnable. The code which you want to run periodically.
        Runnable task = new Runnable() {

            @Override
            public void run() {

                System.out.println("test");
            }
        };

        // Get an instance of scheduler
        final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
        // execute scheduler at fixed time.
        scheduler.scheduleAtFixedRate(task, startScheduler, stopScheduler, MILLISECONDS);
    }
}

参考： https ://chynten.wordpress.com/2016/06/03/java-scheduler-to-run-every-day-on-specific-time/

score 0 · Accepted Answer

如果你可以像这样写，为什么要把情况复杂化？（是的 -> 低内聚，硬编码 -> 但这是一个例子，不幸的是使用命令式的方式）。有关其他信息，请阅读下面的代码示例；））

package timer.test;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.time.Duration;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.util.concurrent.*;

public class TestKitTimerWithExecuterService {

    private static final Logger log = LoggerFactory.getLogger(TestKitTimerWithExecuterService.class);

    private static final ScheduledExecutorService executorService 
= Executors.newSingleThreadScheduledExecutor();// equal to => newScheduledThreadPool(1)/ Executor service with one Thread

    private static ScheduledFuture<?> future; // why? because scheduleAtFixedRate will return you it and you can act how you like ;)



    public static void main(String args[]){

        log.info("main thread start");

        Runnable task = () -> log.info("******** Task running ********");

        LocalDateTime now = LocalDateTime.now();

        LocalDateTime whenToStart = LocalDate.now().atTime(20, 11); // hour, minute

        Duration duration = Duration.between(now, whenToStart);

        log.info("WhenToStart : {}, Now : {}, Duration/difference in second : {}",whenToStart, now, duration.getSeconds());

        future = executorService.scheduleAtFixedRate(task
                , duration.getSeconds()    //  difference in second - when to start a job
                ,2                         // period
                , TimeUnit.SECONDS);

        try {
            TimeUnit.MINUTES.sleep(2);  // DanDig imitation of reality
            cancelExecutor();    // after canceling Executor it will never run your job again
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        log.info("main thread end");
    }




    public static void cancelExecutor(){

        future.cancel(true);
        executorService.shutdown();

        log.info("Executor service goes to shut down");
    }

}

score -1 · Accepted Answer

在这里，假设代码在单个 VM 上运行。如果代码在多个 VM 上运行，则此调度程序代码将运行多次。那得分开处理。

java - 如何使用 ScheduledExecutorService 每天在特定时间运行特定任务？

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