@Scheduled annotation should support property placeholder values [SPR-6670]

[spring-projects-issues]

Mark Fisher opened SPR-6670 and commented

This would promote externalization of the actual scheduling configuration.

Rather than:

@Scheduled(cron = "0 0 9-17 * * MON-FRI")
public void doSomething() {...}

The cron expression could be in a properties file, so the annotation no longer contains a hard-coded value:

@Scheduled("${schedules.businessHours}")
public void doSomething() {...}

This should also work with meta-annotations, e.g.:

@Scheduled(cron = "${schedules.businessHours}")
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)	
public @interface BusinessHours {}

...would apply to:

@BusinessHours
public void doSomething() {...}

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Affects: 3.0 GA

Issue Links:

• @Scheduled's int attributes do not allow for placeholder values [SPR-8067] #12722 @Scheduled's int attributes do not allow for placeholder values

Referenced from: commits 410dd0a

[spring-projects-issues]

Flemming Jønsson commented

The support for property placeholder values only goes for the cron (String) parameter. Is there any chance this could be extended to also be possible for fixedDelay and fixedRate (both of type long).

[spring-projects-issues]

Mark Fisher commented

Since fixedDelay and fixedRate are of type long, they cannot accept a String value. Therefore, we cannot provide support for property placeholders since that would require actually providing String values in the annotation. The only option would be to add further String-typed attributes specifically for that purpose, but it seems like that could lead to confusion. When using the XML support via <scheduled-tasks>, property placeholders can be used even for the fixed-delay and fixed-rate, because the extra processing step of XML parsing is always dealing with text anyways. It's unfortunately not that simple with the annotation support.