How to get next run time Spring Scheduling?

Question

I am working on a scheduling project which executes multiple jobs at regular intervals. I am using a cron scheduling as in the example below. The jobs are getting executed successfully no problems. However for a requirement I want to calculate and persist the next run time of the Scheduled job in DB. Is there a solution to get next and previous fire times of jobs for the configuration below?

Example configuration:

import java.util.Date;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Component;

@Component
@EnableScheduling
public class DemoServiceBasicUsageCron
{   
    @Scheduled(cron="1,3,30,32 * * * * ?")
    public void demoServiceMethod()
    {
        System.out.println("Curent date time is - "+ new Date());
    }

}

Answer 1

You can use CronExpression for Spring Framework 5.3 and newer. Use CronSequenceGenerator for older versions. Both of them have same methods. But CronSequenceGenerator is deprecated.

import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.scheduling.support.CronExpression;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import java.util.Date;

@Component
public class MyJob {

    public static final String CRON_EXPRESSION = "0 0 5 * * *";

    @PostConstruct
    public void init() {
        //Update: Resolve compile time error for static method `parse`
        CronExpression cronTrigger = CronExpression.parse(CRON_EXPRESSION);

        LocalDateTime next = cronTrigger.next(LocalDateTime.now());

        System.out.println("Next Execution Time: " + next);
    }

    @Scheduled(cron = CRON_EXPRESSION)
    public void run() {
        // Your custom code here
    }
}

Answer 2

I hope you are using Quartz. you can try something like this.

CronExpression exp = new CronExpression("1,3,30,32 * * * * ?");
exp.getNextValidTimeAfter(new Date());