How to do it...

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

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

1. 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()); 
} 

1. 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.