调度executors

the command-line runners can be used as a place to start the scheduled executor thread pool in order to run the worker threads in intervals.虽然这是可行的，但Spring为我们提供了一个更简洁的配置来完成同样

的目标：@EnableScheduling

 

先给Application类加上@EnableScheduling注解

@SpringBootApplication

@EnableScheduling

public class BookPubApplication {

 

@Bean

public StartupRunner schedulerRunner() {

return new StartupRunner();

}

 

public static void main(String[] args) {

SpringApplication.run(BookPubApplication.class, args);

}

 

}

 

@Scheduled只能用在无参方法上

public class StartupRunner implements CommandLineRunner {

    Log logger = LogFactory.getLog(getClass());

 

    @Autowired

    private BookRepository bookRepository;

 

    @Override

    public void run(String... args) throws Exception {

        logger.info("Number of books: " + bookRepository.count());

    }

 

    @Scheduled(initialDelay = 1000, fixedRate = 3000)

    public void run() {

        logger.info("Number of books: " + bookRepository.count());

    }

}

 

@EnableScheduling不是一个Spring Boot注解，而是一个Spring Context模块注解。它和

@SpringBootApplication以及@EnableAutoConfiguration一样都是元注解。它在内部利用@Import

导入了SchedulingConfiguration，而它又会创建ScheduledAnnotationBeanPostProcessor，接着

扫描那些存在@Scheduled注解的Spring Beans，对于每一个无参的被注解的方法，相应的executor

thread pool会被创建出来。