I am trying to hook into the creation of the context using a custom application listener like this
@Component
public class ContextStartedListener implements ApplicationListener<ContextStartedEvent> {
@Override
public void onApplicationEvent(ContextStartedEvent event) {
System.out.println("Context started"); // this never happens
}
}
But the onApplicationEvent
method never fires. If I use a different event such as ContextRefreshedEvent
then it works just fine, but I need to hook into before it is created. Any advice? Thanks!
[Edit]
Editing answer adding more info because of the downvote.
The reason why you are not getting a callback by the listener is because you are not explicitly calling the LifeCycle start()
method ( JavaDoc ).
This cascades down to your ApplicationContext normally via the AbstractApplicationContext on in Spring Boot case via the ConfigurableApplicationContext .
Example of working code below demonstrating how your callback would work (just explicitly call the start() method)
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationListener;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.event.ContextStartedEvent;
import org.springframework.stereotype.Component;
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
ConfigurableApplicationContext applicationContext = SpringApplication.run(DemoApplication.class, args);
applicationContext.start();
}
@Component
class ContextStartedListener implements ApplicationListener<ContextStartedEvent> {
@Override
public void onApplicationEvent(ContextStartedEvent event) {
System.out.println("Context started");
}
}
}
The reason why I suggested below the ContextRefreshedEvent
callback instead is because behind the scenes the refresh()
code is getting invoked.
If you drill down the SpringApplication#run()
method you'll eventually see it .
Again here's a working example of how this would work using the ContextRefreshedEvent
:
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
@Component
class ContextStartedListener implements ApplicationListener<ContextRefreshedEvent> {
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
System.out.println("Context refreshed");
}
}
}
[Before Edit]
Change the Generic type to ContextRefreshedEvent
instead and then it should work.
For more details read this article from the Spring Blog . Just to quote the part about the ContextRefreshedEvent
:
[..]This allows MyListener to be notified when the context has refreshed and one can use that to run arbitrary code when the application context has fully started.[..]
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