Earlier in this chapter, we discussed how the command-line runners can be used as a place to start the scheduled executor thread pools to run the worker threads in intervals. While that is certainly a possibility, Spring provides you with a more concise configuration to achieve the same goal: @EnableScheduling.

We will enhance our application so that it will print a count of books in our repository every 10 seconds. To achieve this, we will make the necessary modifications to the BookPubApplication and StartupRunner classes.

1. Let's add an @EnableScheduling annotation to the BookPubApplication class, as follows:

@SpringBootApplication 
@EnableScheduling 
public class BookPubApplication {...}

2. As a @Scheduled annotation can be placed only on methods without arguments, let's add a new run() method to the StartupRunner class and annotate it with the @Scheduled annotation, as shown in the following line:

@Scheduled(initialDelay = 1000, fixedRate = 10000) 
public void run() { 
    logger.info("Number of books: " +  
        bookRepository.count()); 
} 

3. Start the application by executing ./gradlew clean bootRun from the command line so as to observe the Number of books: 0 message that shows in the logs every 10 seconds.

@EnableScheduling, as many other annotations that we have discussed and will discuss in this book, is not a Spring Boot; it is a Spring Context module annotation. Similar to the @SpringBootApplication and @EnableAutoConfiguration annotations, this is a meta-annotation and internally imports SchedulingConfiguration via the @Import(SchedulingConfiguration.class) instruction, which can be found inside ScheduledAnnotationBeanPostProcessor that will be created by the imported configuration and will scan the declared Spring beans for the presence of the @Scheduled annotations. For every annotated method without arguments, the appropriate executor thread pool will be created. It will manage the scheduled invocation of the annotated method.