Should Scheduled Task start a Spring application each time it is executed? - spring

Question

I'm running a spring boot application with a scheduled task. It is divided into two maven projects, lets call them 'lib' and 'app'.
The class whose method is annotated with #Scheduled is located in 'lib' project. It does not contain any classes annotated with #SpringBootApplication, or any classes that start a spring application. Here's what Scheduled bean looks like:
#Component
public class Refresher {
#Scheduled(fixedRate = 30000)
public void refresh() {
...
}
The 'lib' project also has a simple SchedulingConfigurer implementation that tells Spring to use ThreadPoolTaskScheduler with its Scheduled tasks.
The 'app' project, on the other hand, has a dependency on 'lib' and has a class annotated with #SpringBootApplication, and starts it as usual:
#SpringBootApplication(scanBasePackages = {"x.y", "x.y.z"})
#EnableScheduling
public class ExampleService {
public static void main(String[] args) {
SpringApplication.run(ExampleService.class, args);
}
}
Both maven projects have this:
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.5.RELEASE</version>
<relativePath/>
</parent>
So, when ExampleService starts I see it finds Refresher and executes its refresh method once every 30 sec alright, but something strange appears in the logs. When Example service starts, it prints:
2019-01-11 18:18:27.647 INFO 6428 --- [ main] x.y.z.ExampleService : Started ExampleService in 32.613 seconds (JVM running for 40.37)
This is great, it tells me that main application has started. But then I get the following lines every 30 seconds, every time Refresher gets executed:
2019-01-11 18:18:58.596 INFO 6428 --- [nio-8080-exec-3] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext#66e31414: startup date [Fri Jan 11 18:18:58 MSK 2019]; root of context hierarchy
2019-01-11 18:18:58.637 INFO 6428 --- [nio-8080-exec-3] trationDelegate$BeanPostProcessorChecker : Bean 'configurationPropertiesRebinderAutoConfiguration' of type [org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration$$EnhancerBySpringCGLIB$$7c355e31] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
... some logging from the refresh() method
2019-01-11 18:19:01.020 INFO 6428 --- [nio-8080-exec-3] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext#1262db58: startup date [Fri Jan 11 18:19:01 MSK 2019]; parent: org.springframework.context.annotation.AnnotationConfigApplicationContext#66e31414
2019-01-11 18:19:01.035 INFO 6428 --- [nio-8080-exec-3] o.s.boot.SpringApplication : Started application in 3.585 seconds (JVM running for 73.771)
2019-01-11 18:19:01.035 INFO 6428 --- [nio-8080-exec-3] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext#1262db58: startup date [Fri Jan 11 18:19:01 MSK 2019]; parent: org.springframework.context.annotation.AnnotationConfigApplicationContext#66e31414
2019-01-11 18:19:01.035 INFO 6428 --- [nio-8080-exec-3] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext#66e31414: startup date [Fri Jan 11 18:18:58 MSK 2019]; root of context hierarchy
Notice 'Started application in 3.585 seconds (JVM running for 73.771)'. This happens every 30 seconds. It looks like in order to run the Scheduled bean Spring runs a new separate Spring application every time. Why would it do that, and can this be avoided? Can Scheduled bean run as part of currently started Spring Boot app?