How to inject HttpServletRequest into a Spring AOP request (custom scenario)?

Question

I know the standard way of writing an AOP advice around a controller method and that you can get access to the HttpServletRequest arg, if declared in controller method.

But my scenario is that I have a translation service, that is currently session-scoped maintaining the user's locale for translation. I feel this makes the service stateful and also I do not want it to be session-scoped, as I think it is really Singleton. But there are multiple places where the translation service methods are called and so I do not want to change the signature to add request/locale in these methods. The problem is that all the callers of the translation service's methods do not have access to HttpServletRequest (not controller methods)? Can I write an aspect around the translation service methods and somehow magically get access to HttpServletRequest regardless of whether it is available in the caller's context or not?

@Service
public class TranslationService {
    public void translate(String key) {
        ...
    }
}

@Aspect
@Component
public class LocaleFinder {
    @PointCut("execution(* TranslationService.translate(..))")
    private void fetchLocale() {}

    @Around("fetchLocale()") // in parameter list
    public void advice(JoinPoint joinpoint, HttpServletRequest request) { .... } 
}

If now, the caller of translate does not have HttpServletRequest, can't I get request in the advice? Is there a workaround?

Answer 1

You should be able to auto-wire a HttpServletRequest in your aspect. Spring provides a proxy to the current thread local request instance that way.

So just add:

@Autowired private HttpServletRequest request;

to your aspect. Better yet is to use constructor injection.