java - How to change Spring's @Scheduled fixedDelay at runtime?

Question

I have a requirement to run a batch job at a fixed interval and have the ability to change the time of this batch job at runtime. For this I came across @Scheduled annotation provided under Spring framework. But I'm not sure how I'd change the value of fixedDelay at runtime. I did some googling around but didn't find anything useful.

Answer 1

In spring boot, you can use an application property directly!

For example:

@Scheduled(fixedDelayString = "${my.property.fixed.delay.seconds}000")
private void process() {
    // your impl here
}

Note that you can also have a default value in case the property isn't defined, eg to have a default of "60" (seconds):

@Scheduled(fixedDelayString = "${my.property.fixed.delay.seconds:60}000")

---

Other things I discovered:

• the method must be void
• the method must have no parameters
• the method may be private

I found being able to use private visibility handy and used it in this way:

@Service
public class MyService {
    public void process() {
        // do something
    }

    @Scheduled(fixedDelayString = "${my.poll.fixed.delay.seconds}000")
    private void autoProcess() {
        process();
    }
}

Being private, the scheduled method can be local to your service and not become part of your Service's API.

Also, this approach allows the process() method to return a value, which a @Scheduled method may not. For example, your process() method can look like:

public ProcessResult process() {
    // do something and collect information about what was done
    return processResult; 
}

to provide some information about what happened during processing.