Spring ApplicationListener gets fired twice on webapp

Question

I have an application listener that's supposed to execute only once per webapp startup, since it loads basic user info data.

public class DefaultUsersDataLoader implements ApplicationListener<ContextRefreshedEvent> {
  @Override
  @Transactional
  public void onApplicationEvent(ContextRefreshedEvent e) {...}
}

Somehow, it gets executed twice: on app startup and when the first request arrives to the server. Why is this happening and how can I prevent it?

Answer 1

Generally in a Spring MVC application you have both a ContextLoaderListener and DispatcherServlet. Both components create their own ApplicationContext which in turn both fire a ContextRefreshedEvent.

The DispatcherServlet uses the ApplicationContext as created by the ContextLoaderListener as its parent. Events fired from child contexts are propagated to the parent context.

Now if you have an ApplicationListener<ContextRefreshedEvent> defined in the root context (the one loaded by the ContextLoaderListener) it will receive an event twice.