SpringBoot – @Scheduled Annotation with Examples

SpringBoot – @Scheduler Annotation with Examples

In our applications we might need certain logic or method that needs to be executed at certain intervals. For ex: We might require a method to be executed every 15 min.

In SpringBoot we have an annotation to achieve this, @Scheduled annotation. From package –  org.springframework.scheduling.annotation.Scheduled.

@Scheduled types,

• initialDelay
• fixedRate
• fixedDelay
• fixedDelayString
• cron

initialDelay:

• The milliseconds delay before the execution of fixedRate or fixedDelay

fixedRate:

• Invocation with specific period of time

fixedDelay:

• Fixed period between the last invocation and the next invocation

fixedDelayString:

• Same as fixedDelay but this accepts string parameter
• Example: @Scheduled(fixedDelayString = “5000”)

Now for example, if we pass incorrect number as string to fixedDelayString what will happen?

Let us pass this,
@Scheduled(fixedDelayString = “5000r“)
When we try to run this, we will get an exception

org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘myApplication’: Initialization of bean failed; nested exception is java.lang.IllegalStateException: Encountered invalid @Scheduled method ‘ScheduledFixedRate’: Invalid fixedDelayString value “5000r” – cannot parse into integer

Cron:

• A cron-like expression which has 6 arguments – Minutes, Hour, Date, Month, Week and Year
• It looks like @Scheduled(cron = “* * * * * *”)

Now let us see an detailed example,

@SpringBootApplication
@EnableScheduling
public class MyApplication {
   
    public static void main(String[] args) throws Exception {
	SpringApplication.run(MyApplication.class, args);
    }
    
    @Scheduled(fixedDelayString = "5000")
    public void ScheduledFixedRate(){
        Calendar cal = Calendar.getInstance();
        System.out.println("Scheduler with FixedRate: "+cal.getTime());
    }
    
    @Scheduled(fixedDelay = 7000)
    public void ScheduledFixedDelay(){
        Calendar cal = Calendar.getInstance();
        System.out.println("Scheduler with FixedDelay: "+cal.getTime());
    }
    
    @Scheduled(cron = "10 02 21 * * *")
    public void ScheduledCron(){
        Calendar cal = Calendar.getInstance();
        System.out.println("Cron Job: "+cal.getTime());
    }
}

In the above example we have scheduled a cron,

@Scheduled(cron = “10 02 21 * * *”) – This will execute exactly on 21:02:10 – 21 hours, 02 minutes 10 seconds

When the above code is executed,