//где-то в контроллере
    @AssertEntityExistsById(entityClass = User.class)
    @RequestMapping(value = "/{id}", method = RequestMethod.GET)
    @ResponseBody
    public User getUser(@PathVariable("id") @EntityIdentifier int id) {
        return userService.findUserById(id);
    }

    //эдвайс
    @Around("@annotation(assertEntityExistsById) && args(..)")
    public Object assertEntityExists(ProceedingJoinPoint proceedingJoinPoint, AssertEntityExistsById assertEntityExistsById) throws Throwable {
        MethodSignature methodSignature = (MethodSignature) proceedingJoinPoint.getSignature();
        Object[] arguments = proceedingJoinPoint.getArgs();
        Object id = null;

        List<Parameter> parameters = Arrays.asList(methodSignature.getMethod().getParameters());

        for (int index = 0; index < parameters.size(); index++) {
            Parameter parameter = parameters.get(index);
            List<Annotation> parameterAnnotations = Arrays.asList(parameter.getAnnotations());

            for (Annotation annotation: parameterAnnotations) {
                if (annotation instanceof EntityIdentifier) {
                  id = arguments[index];
                }
            }
        }

        Repositories repositories = RepositoriesSingleton.getInstance();
        JpaRepository jpaRepository = (JpaRepository) repositories.getRepositoryFor(assertEntityExistsById.entityClass()).get();

        if (!jpaRepository.existsById(id)) {
            throw entityNotFoundExceptionFactory.createForEntityClass(assertEntityExistsById.entityClass());
        }

        return proceedingJoinPoint.proceed();
    }