Agfdhyk

I have several Spring Services in my application which are independent from each other. In an init method of the services, annotated with @PostConstruct, some dependencies to external services will be initialized. However if this initialization process fails an error screen with message 500 javax.servlet.ServletException: Servlet.init() exception will be displayed with root cause BeanCreationException of the service who's @PostConstruct init could not be executed successfully.

I understand that in case of a Bean initialization failure the application is not consistent anymore and therefore the whole app might not work as intended. However since the services are independent from the rest of the application I would like to catch this initialization exception and still access the application in some maintenance mode where you will get an error screen in case the page of the service, which could not be initialized, should be accessed.

I tried several approaches using a Global Controller Exception annotated with @ControllerAdvice or an @ExceptionHandler method but they wont get triggered. The error screen is displayed immediately.

Another try was using a Filter or a HandlerExceptionResolver, but both don't get triggered in this case.

After some research I found some discussions that this error is fatal and therefore cannot be handled or cached. Also it seem that the exception is thrown before the request is passed to the controller handle method or any configured filter, therefore the controller exception handler are not triggered as well.

My questions is now: Is there any other approach which I am still missing in order to handle BeanCreationExceptions? The final solution should start the application in some maintenance mode which offers an error screen when the failed Bean/Service should be accessed, or give some information about failed initialized services.

Thank in advance for anyone how has some hints or further explanation.

I found some workaround which might help someone else facing the same issue, so I would like to share my approach.

I ended up using a combination of the @Conditional annotation, which manages the creation of beans and a customer error page, configured in web.xml.

Basically, I used @Conditional on every service which depends on external resources. The Condition checks if any needed external dependencies can be initialized.
If the matches method of the Condition returns true the service annotated with my Condition class will be created otherwise spring ignores the creation of the bean for that service.

Here is an example of my Condition implementation (I just execute in matches what is contained in the @PostConstruct init method of the service):

public class ModuleCondition implements Condition {



   @Override

   public boolean matches(ConditionContext arg0, AnnotatedTypeMetadata arg1) {

    if (/*check external dependencies*/)

       return true;

    else

       return false;

  }

}

and here is the an example of using the Condition:

@Service

@Conditional(value = ModuleCondition.class)

public class MyService {

     ...

}

In order to handle the 404 error on case the interface of the service which could not be initialized I used a customer error page and a CustomerErrorController. (I followed the following tutorial here)

So, in case a service cannot be initialized, which got caused by a failed initialization of external resources, the user will be forwarded to a customer error page informing the user that the accessed module is currently not available.