How to disable @Scheduled method via properties file?

Question

I have a Spring scheduled method that is periodically run:

@Scheduled(cron = "${spring.cron.expression}")
public void demonJob() { ... }

The cron expression is successfully read from the application.properties:

spring.cron.expression=0 0 * * * *

Now, I want to deploy my application to a special environment on which this particular scheduled method is not supposed to run. If I leave the cron property empty like this...

spring.cron.expression=

... I get the following exception:

Encountered invalid @Scheduled method 'demonJob': Cron expression must consist of 6 fields (found 0 in "")

How can I disable the Scheduled method elegantly, ideally only by providing a different setting in application.properties?

Answer 1

As of Spring 5.1.0, the special cron value "-" can be used with the @Scheduled annotation to disable the cron trigger.

The special value "-" indicates a disabled cron trigger, primarily meant for externally specified values resolved by a ${...} placeholder.

For your specific example, you merely need to set the spring.cron.expression variable to this value. If this is a Spring Boot project, you can use one of the many externalized configuration options available for this purpose, including:

• Command line argument
• Java System property
• OS environment variable
• Profile-specific application property for a profile used specifically for that environment

If this is not a Spring Boot project, you can still specify this property, though the mechanism to do so is going to be less standard and more project specific.