控制器checkEmail为“ false”返回“错误解析JSON：undefined false”，“ true”按预期工作

Question

I've got a little problem with returning false from controller. First off, true is being returned normally as "true" in JSON without any problem, but when it should return false this is displayed :

Error parsing JSON: undefined
undefined:

false

Here is my DAO

@Override
    public Boolean checkEmail(String email) {
        System.out.println(email);
        Query query = em.createQuery("SELECT s FROM StudenciEntity s WHERE s.email LIKE :email");
        query.setParameter("email", email);
        if (query.getResultList().isEmpty()) {
            return false;
        }
        else {
            return true;
        }
    }

Here is Controller

@RequestMapping(value = "/email/{email:.+}", method = RequestMethod.GET)
    public ResponseEntity<Boolean> checkEmail(@PathVariable String email) {
        Boolean checkEmail = istudenciService.checkEmail(email);
        if (checkEmail !=null) {
            return new ResponseEntity<Boolean>(checkEmail, HttpStatus.OK);
        }
        else {
            return new ResponseEntity<Boolean>(HttpStatus.NOT_FOUND);
        }
    }

At the beginning i was returning Long for email (1 and -1) and it worked, then wanted to make it boolean and all this happened.