java listen to ContextRefreshedEvent

java, javabeans, spring

Solution

A `ContextRefreshEvent` occurs

when an `ApplicationContext` gets initialized or refreshed.

so you are on the right track.

What you need to do is declare a bean definition for `classX`.

Either with `@Component` and a component scan over the package it's in

@Component
public class X implements ApplicationListener<ContextRefreshedEvent> {
    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
       //do something if all apps have initialised
    }
}

or with a `<bean>` declaration

<bean class="some.pack.X"></bean>

Spring will detect that the bean is of type `ApplicationListener` and register it without any further configuration.

Later Spring version support annotation-based event listeners. The documentation states

As of Spring 4.2, you can register an event listener on any public method of a managed bean by using the `@EventListener` annotation.

Within the `X` class above, you could declare an annotated method like

@EventListener
public void onEventWithArg(ContextRefreshedEvent event) {
}

or even

@EventListener(ContextRefreshedEvent.class)
public void onEventWithout() {

}

The context will detect this method and register it as a listener for the specified event type.

The documentation goes into way more detail about the full feature set: conditional processing with SpEL expression, async listeners, etc.

Just FYI, Java has naming conventions for types, variables, etc. For classes, the convention is to have their names start with an uppercase alphabetic character.

Problem

I have a classX in my spring application in which I want to be able to find out if all spring beans have been initialized. To do this, I am trying to listen ContextRefreshedEvent. So far I have the following code but I am not sure if this is enough. ``` import org.springframework.context.ApplicationListener; import org.springframework.context.event.ContextRefreshedEvent; public classX implements ApplicationListener<ContextRefreshedEvent> { @Override public void onApplicationEvent(ContextRefreshedEvent event) { //do something if all apps have initialised } } ``` - Is this approach correct to find out if all beans have initialsed? - What else do I need to do to be able to listen to the ContextRefreshedEvent ? DO I need to register classX somewhere in xml files ?

Original source