ScheduledExecutorService.scheduleAtFixedRate并将过去的initialDelay设置为日期 [英] ScheduledExecutorService.scheduleAtFixedRate And Setting initialDelay To Date In The Past

问题描述

我正在使用Java计划系统，该系统基于 startDate ， endDate 和发生(每小时，每天)发出提醒，每周，每月，星期一等).最初，我是使用 Timer 和 TimerTask 类来安排提醒的时间:

Timer timer = new Timer();
timer.scheduleAtFixedRate(reminder, firstDate, period);

我最近切换到了 ScheduledExecutorService ，因此我可以对取消事件进行更多控制. ScheduledExecutorService 对于重复提醒非常有效，除了过去使用 startDate 重新安排提醒的一种情况. scheduleAtFixedRate 函数仅允许您为 initialDelay 指定 long 值，而不是实际的 Date 对象:

ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
scheduler.scheduleAtFixedRate(reminder, initialDelay, period, unit);

这带来了一个问题，因为传入负的 initialDelay 仍然会导致事件立即被触发，从而导致事件在 now + 期间再次发生，而不是 startDate + 期间.

有什么想法可以让我过去通过 startDate 来(重新)安排提醒时间吗?

解决方案

只需快速检查一下日期是否为过去的日期，然后创建一个新的临时开始日期时间即可，即现在开始的时间增量./p>

I'm working on a scheduling system in Java that sends out reminders based on a startDate, endDate and occurrence (hourly, daily, weekly, monthly, Mondays, etc). Originally I was using Timer and TimerTask classes to schedule the reminders:

Timer timer = new Timer();
timer.scheduleAtFixedRate(reminder, firstDate, period);

I recently switched to ScheduledExecutorService so I could have more control on cancelling events. The ScheduledExecutorService is working well for recurring reminders, except for the one case of rescheduling a reminder with a startDate in the past. The scheduleAtFixedRate function only allows you to specify long value for initialDelay, and not an actual Date object:

ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
scheduler.scheduleAtFixedRate(reminder, initialDelay, period, unit);

This poses a problem, since passing in a negative initialDelay still causes the event to be fired immediately thus causing it to reoccur at now + period, rather than startDate + period.

Any ideas how I can (re)schedule a reminder with the startDate in the past?

解决方案

Just do a quick check to see if the date is in the past, then create a new temporary start datetime that is the increment of the start past now.

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