Spring The Boot container performs specific operations when loaded. of recommends

In some cases we need to do something after the Spring container has been started and loaded, in which case we can implement ApplicationListener < E extends ApplicationEvent > Interface and specify events to perform operations, such as starting some custom daemon threads

ApplicationContextEvent is the base class for events raised by ApplicationContext, which has several implementation classes:

ContextRefreshedEvent: This event is emitted when the ApplicationContext container is initialized or refreshed. This event is executed once
ContextStartedEvent: This event is emitted when the ApplicationContext container is started using the start() method of the ConfigurableApplicationContext interface
ContextClosedEvent: This event is emitted when the ApplicationContext container is closed using the close() method of the ConfigurableApplicationContext interface
ContextStopedEvent: This event is emitted when the ApplicationContext container is stopped using the stop() method of the ConfigurableApplicationContext interface

The code example

@Component
public class ApplicationStartup implements ApplicationListener<ContextRefreshedEvent> {
 @Override
 public void onApplicationEvent(ContextRefreshedEvent event) {
  System.out.println(" This event is emitted when the container is initialized or refreshed , perform 1 time ");
 }
}

conclusion