Based on spring documentation @ControllerAdvice is annotated with @Component which means it will be scanned by Spring Boot normally.

So, let's focus on your calss implementation, I see you are depending on the @ExceptionHandler(ApplicationContextException.class) although you want to listen to application failed event, right? I have good news ! there is something ready to use already provided by springboot, the ApplicationFailedEvent.

All what you need is just to create a custom expetion handler that listen for the ApplicationFailedEvent, I have tweaked you code submitted above to work as the explanasion above:

@ControllerAdvice
public class GenericExceptionHandler implements ApplicationListener<ApplicationFailedEvent> {
    private static final Logger log = LoggerFactory.getLogger(GenericExceptionHandler.class);

    @Value("${server.port}")
    private String serverPort;


    @Override
    public void onApplicationEvent(ApplicationFailedEvent event) {
        Throwable exception = event.getException();
        if (exception instanceof ApplicationContextException
                && exception.getCause() instanceof PortInUseException) {
            log.error("Port Already in use, Refer Step 3.1 for configuring new port");
            System.exit(1);
        }
    }

}