Is it possible to assign @Scheduled with a period representing "never" (in Spring)?

Question

I'm investigating using @Scheduled at a fixed rate where in some configurable circumstances the scheduled job should never be run.

The documentation doesn't mention this but the default values for fixedDelay() and fixedDelayString() are -1 and "" respectively. Can these be used to reliably ensure that the scheduled method doesn't fire?

Answer 1

You can not. When you set the fixedDelay attribute to -1 or attempt use @Scheduled without specifying a valid value for any of its attributes, Spring will complain that no attribute is set:

Exactly one of the 'cron', 'fixedDelay(String)', or 'fixedRate(String)' attributes is required

You can verify this behavior by going through the source code of ScheduledAnnotationBeanPostProcessor#processScheduled.

It contains logic like:

boolean processScheduled = false;

// ...

if (fixedRate >= 0) {
    Assert.isTrue(!processedSchedule, errorMessage);
    processedSchedule = true;
    this.registrar.addFixedRateTask(new IntervalTask(runnable, fixedRate, initialDelay));
}

// ...

Assert.isTrue(processedSchedule, errorMessage);

Take a look at this SO post for some options for conditionally disabling @Scheduled.

Answer 2

As mentioned in spring docs, you can specify "-" to disable the triggering of the task:

CRON_DISABLED: A special cron expression value that indicates a disabled trigger: "-".

https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/scheduling/annotation/Scheduled.html#CRON_DISABLED