In my Spring application, I have an abstract class with a function functionA and an abstract function functionB. functionA calls functionB and the latter is implemented in the child classes.

I want functionA to be a scheduled function (running based on a cron string) in all the child classes, but the schedule in each child class is different.

I considered using @Scheduled annotation in the abstract class' functionA, with the child classes having @Component annotations. But I am unable to figure out how to control the cron strings for each child class.

How do i achieve this? Is there a way to make the cron value in the @Scheduled annotation accept a class variable?

In my Spring application, I have an abstract class with a function functionA and an abstract function functionB. functionA calls functionB and the latter is implemented in the child classes.

I want functionA to be a scheduled function (running based on a cron string) in all the child classes, but the schedule in each child class is different.

I considered using @Scheduled annotation in the abstract class' functionA, with the child classes having @Component annotations. But I am unable to figure out how to control the cron strings for each child class.

How do i achieve this? Is there a way to make the cron value in the @Scheduled annotation accept a class variable?

• spring
• spring-scheduled

1 Answer 1

I do not know how you can achieve what you want using @Scheduled in an abstract class and defining the cron expression in its implementations.
I guess it is either impossible or, at the very least, not simple.

But I would suggest the following approach:

• add one more abstract method getCronTrigger
• implement getCronTrigger in the abstract class's implementation so they return needed CronTrigger
• schedule tasks in some post construct
  • using autowired list of all beans that implement the abstract class
  • using autowired taskScheduler

The approach is inspired by baeldung and another SO answer
But there are changes for your specific question.
Example is written in Kotlin, but it could be easily rewritten to Java.

@Configuration
// EnableScheduling is needed to have bean ThreadPoolTaskScheduler in the Spring context
// other approach - define your own bean ThreadPoolTaskScheduler
@EnableScheduling
class ScheduledConfigs

@Component
class Schedule(
    private val tasks: List<ScheduledTask>,
    private val taskScheduler: ThreadPoolTaskScheduler
) {
    @PostConstruct
    fun schedule() {
        for (task in tasks) {
            println("Schedule task (${task.javaClass.simpleName}) with cron ${task.getCronTrigger()}")
            taskScheduler.schedule(task, task.getCronTrigger());
        }
    }
}

abstract class ScheduledTask: Runnable {
    override fun run() {
        println("${javaClass.simpleName} starts")
        doWork()
        println("${javaClass.simpleName} did its work")
    }
    abstract fun doWork()
    abstract fun getCronTrigger(): CronTrigger
}

@Component
class RealTask1: ScheduledTask() {
    override fun getCronTrigger(): CronTrigger = CronTrigger("*/30 * * * * ?")
    override fun doWork() {
        println("${javaClass.simpleName} does its job every 30 seconds")
    }
}

@Component
class RealTask2: ScheduledTask() {
    override fun getCronTrigger(): CronTrigger = CronTrigger("0 * * * * ?")
    override fun doWork() {
        println("${javaClass.simpleName} does its job every minute")
    }
}