Spring Scheduled task does not start on application startup

Question

I have a @Scheduled task in my application which is setup using CRON and run every 4 hours. The problem I face is that the CRON job does not start immediately after application startup but it starts only 4 hours after the application startup.

I tried to use a @PostConstruct method inside the task to invoke it, but that results in an error due to an uninitialized Spring context.

Please tell me how I can make the Scheduled task run immediately on application deployment and then on every 4 hours after the deployment.

EDIT:
I would not use a @PostConstruct since my scheduled method depends on other Beans , which are not initialized when this PostConstruct method runs for some reason.

Answer 1

By 0 */4 * * * you specify "At minute 0 past every 4th hour (0:00, 4:00, 8:00 etc.)", which is not at startup time and then every 4 hours as I think you want. You can specify initial delay and rate by:

@Scheduled(initialDelay=0, fixedRate=4*60*60*1000)

If you are worried about hard-coded values, you can still provide config value:

@Scheduled(initialDelay=0, fixedRateString = "${some.config.string}")

Answer 2

I had @EnableScheduling in my app config. I had @Scheduled(fixedDelay=5000) in my scheduled task class. Even then it didn't work.

I added @Service to my scheduled task class and everything worked fine.

Answer 3

I was having the same situation. I need to run cron scheduler every 1st day of the month and also when the application starts.

This is how I achieved using ApplicationListener.

import org.springframework.context.ApplicationListener;
import org.springframework.boot.context.event.ApplicationReadyEvent;

@Component
public class ApplicationReadyListner implements ApplicationListener<ApplicationReadyEvent> {
    @Override
    public void onApplicationEvent(ApplicationReadyEvent event) {
        // callYourTask();
    }
}

Answer 4

I'm not sure if you have tried this but you can use @Scheduled with an initialDelay

For fixed-delay and fixed-rate tasks, an initial delay may be specified indicating the number of milliseconds to wait before the first execution of the method.

https://docs.spring.io/spring/docs/current/spring-framework-reference/html/scheduling.html#scheduling-annotation-support-scheduled

@Scheduled(initialDelay=0, fixedRate=5000)
public void doSomething() {
    // something that should execute periodically
}

I assume this will execute your scheduled method when the application is run.

Answer 5

If is not possible to use initialDelay attribute with the cron rule and your intention is execute this Job after every restart, you can implement a CommandLineRunner on your application class:

@SpringBootApplication
public class MyApplication implements CommandLineRunner {

    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }

    @Autowired
    private TaskService taskService;

    @Override
    public void run(final String... args) throws Exception {

        taskService.run();
    }

}

It's not the best strategy, but works.

Answer 6

Just specify the method you want to run in the init_method attribute of the bean.

Java config: @Bean(init_method="methodWhichStartsTask")

XML config: <bean id="someId" class="com.example.Clazz" init-method="methodWhichStartsTask"/>

This will invoke the method just after the bean is properly initialized and if the method is scheduled, then it will be called afterwards every 4 hours.

Answer 7

Instead of cron inside @Scheduled, use fixedRate like below. By default initialDelay is -1, which will start immediately or you can set 0.

@Scheduled(fixedRate=4*60*60*1000)
public void test() {
    System.out.println("helloworld");
}

Answer 8

user @EnableScheduling annotation on your class which contains you1 scheduled method:

see spring document:

To enable support for @Scheduled and @Async annotations add @EnableScheduling and @EnableAsync to one of your @Configuration classes:

@Configuration
@EnableAsync
@EnableScheduling
public class AppConfig {
}

link : https://docs.spring.io/spring/docs/current/spring-framework-reference/html/scheduling.html

Answer 9

@EnableScheduling annotation should be added in the main class for the Spring application.

Example :

@SpringBootApplication
@EnableScheduling
public class MyApplication {

public static void main(String[] args) {
    SpringApplication.run(MyApplication.class, args);
}

}

and above the method where the actual scheduling needed we need to add

@Scheduled(initialDelay = 1000, fixedDelay = 4*60*60*1000)

Example:

@Scheduled(initialDelay = 1000, fixedDelay = 4*60*60*1000)
public void schleduleWork() {
    /* Code Here */
}

For the above scheduler the first hit will be at 1000 milli second and subsequest hits will be at the interval of 4 hrs