如何使用 Spring 延迟计划任务？

Question

I'd like to create a method that delays the execution on method invocation by 60s.

Problem: if the method is called within that 60s, I want it to be delayed again by 60s from last point of invocation. If then not called within 60s, the execution may continue.

I started as follows, but of course this is only a one-time delay:

public void sendDelayed(String info) {
   //TODO create a task is delayed by +60s for each method invocation 
   ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
   executorService.schedule(Classname::someTask, 60, TimeUnit.SECONDS);
}

How could I further delay the execution on each invocation?

Answer 1

executorService.schedule returns a ScheduledFuture which provides a cancel method to cancel its execution. cancel takes a single boolean parameter mayInterruptIfRunning which, when set to false , will only cancel the execution if the task has not started yet. See also the docs .

Using this you could do something like this:

private ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();

private ScheduledFuture<?> future;

public void sendDelayed(String info) {
    // When there is a task that has not been started yet, stop it:
    if (future != null) {
        boolean cancelled = future.cancel(false);
        if (cancelled) {
            logger.debug("Task has been cancelled before execution");
        } else {
            logger.debug("Task is already running or has been completed");
        }
    }

    // Old task has been cancelled or already started - schedule a new task
    future = executorService.schedule(Classname::someTask, 60, TimeUnit.SECONDS);
}

You may have to take care of avoiding race conditions regarding concurrent access to the future field though.