not able to publish custom event in spring before context load

问题

I am trying to publish a custom event in Spring MVC, but is is not firing while context is loading, below are the code snippet,

The onConnectionOpened will be called after connecting to a server which is triggered after bean initialization using @PostConstruct

@Autowired
private ApplicationEventPublisher publisher;

public void onConnectionOpened(EventObject event) {
    publisher.publishEvent(new StateEvent("ConnectionOpened", event));

}

I am using annotation in listener part as below

@EventListener
public void handleConnectionState(StateEvent event) {
   System.out.println(event);
}

I am able to see events fired after the context is loaded or refreshed, is this expected that custom application events can be published after the context loaded or refreshed?.

I am using Spring 4.3.10

Thanks in advance

回答1:

The @EventListener annotations are processed by the EventListenerMethodProcessor which will run as soon as all beans are instantiated and ready. As you are publishing an event from a @PostConstruct annotated method it might be that not everything is up and running at that moment and @EventListener based methods haven't been detected yet.

Instead what you can do is use the ApplicationListener interface to get the events and process them.

public class MyEventHandler implements ApplicationListener<StateEvent> {

    public void onApplicationEvent(StateEvent event) {
        System.out.println(event);
    }
}

回答2:

You should publish event after ContextRefreshedEvent occur, but if you wait ContextRefreshedEvent in @PostConstruct, it will make whole applicaiton hang up, so use @Async will solve this problem.

@EnableAsync
@SpringBootApplication
public class YourApplication
    public static void main(String[] args) {
        SpringApplication.run(YourApplication.class, args);
    }
}

@Slf4j
@Service
public class PublishHelper {
    private final ApplicationEventPublisher publisher;

    private final CountDownLatch countDownLatch = new CountDownLatch(1);

    @EventListener(classes = {ContextRefreshedEvent.class})
    public void eventListen(ContextRefreshedEvent contextRefreshedEvent) {
        log.info("publish helper is ready to publish");
        countDownLatch.countDown();
    }

    public PublishHelper(ApplicationEventPublisher publisher) {
        this.publisher = publisher;
    }

    @Async
    @SneakyThrows
    public void publishEvent(Object event) {
        countDownLatch.await();
        publisher.publishEvent(event);
    }
}

来源：https://stackoverflow.com/questions/47271498/not-able-to-publish-custom-event-in-spring-before-context-load

标签

java

Spring

spring-mvc

spring-annotations