Perform actions periodically using Spring Scheduler

Spring Scheduler #

Uses @Scheduled to execute specific code at regular intervals.

Dependency #

Relies on org.springframework.scheduling by default in Spring Boot starter.

Enable Scheduling #

Add @EnableScheduling to the Project Application Class.

@EnableScheduling 
@SpringBootApplication
public class SchedulerApplication {
    public static void main(String[] args) {
        SpringApplication.run(SchedulerApplication.class, args);
    }
}

Add @Component to the class that will use the scheduler, and @Scheduled to the method.

@Scheduled Rules
- Method must be of void type.
- Method cannot use parameters.

fixedDelay #

Executes at milliseconds intervals, based on when the method finishes.

Useful in situations where only one instance should always be running.

@Scheduled(fixedDelay = 1000)
// @Scheduled(fixedDelayString = "${fixedDelay.in.milliseconds}") // 문자열 milliseconds 사용 시
public void scheduleFixedDelayTask() throws InterruptedException {
    log.info("Fixed delay task - {}", System.currentTimeMillis() / 1000);
    Thread.sleep(5000);
}

fixedRate #

Executes at milliseconds intervals, based on when the method starts.

When using Scheduler in parallel, add @EnableAsync to the Class and @Async to the Method.

Useful when all executions are independent.

@Async
@Scheduled(fixedRate = 1000)
// @Scheduled(fixedRateString = "${fixedRate.in.milliseconds}")  // 문자열 milliseconds 사용 시
public void scheduleFixedRateTask() throws InterruptedException {
    log.info("Fixed rate task - {}", System.currentTimeMillis() / 1000);
    Thread.sleep(5000);
}

initialDelay + fixedDelay #

First execution occurs after the initialDelay value, then continues to execute according to the fixedDelay value.

@Scheduled(fixedDelay = 1000, initialDelay = 5000)
public void scheduleFixedRateWithInitialDelayTask() {
    long now = System.currentTimeMillis() / 1000;
    log.info("Fixed rate task with one second initial delay - {}", now);
}

Cron #

Executes as a scheduled task.

@Scheduled(cron = "0 15 10 15 * ?") // 매월 15일 오전 10시 15분에 실행
// @Scheduled(cron = "0 15 10 15 11 ?") // 11월 15일 오전 10시 15분에 실행
// @Scheduled(cron = "${cron.expression}")
// @Scheduled(cron = "0 15 10 15 * ?", zone = "Europe/Paris") // timezone 설정
public void scheduleTaskUsingCronExpression() {
    long now = System.currentTimeMillis() / 1000;
    log.info("schedule tasks using cron jobs - {}", now);
}