Return null in ResponseEntity body (Spring Boot RESTful)

Question

I'm creating a RESTFul Web Service with the following service available:

@RequestMapping(value = "/test", produces = "application/json", method = RequestMethod.GET)
public ResponseEntity<List<GenericModel>> returnEmpty() {
    List<GenericModel> genericModelList = new ArrayList<>();

    HttpHeaders headers = new HttpHeaders();
    headers.add("Content-Type", "application/json; charset=utf-8");

    return responseEntity = new ResponseEntity<>(genericModelList, headers, HttpStatus.OK);
}

When the empty list returns, I'm getting the following response in browser:

[]

How can I do to receive in browser a "null" response instead of []? There's some way to tell Spring to render my list size 0 as "null" and not as []?

Answer 1

One way of pivoting it based on if the genericModelList is empty of not could be:-

if(genericModelList.isEmpty()) {
    return new ResponseEntity<>(null, headers, HttpStatus.OK);
} else {
    return new ResponseEntity<>(genericModelList, headers, HttpStatus.OK);
}

or else you can skip the body using ResponseEntity(MultiValueMap<String,String> headers, HttpStatus status) constructor as well.

Answer 2

Because you just initialize the genericModelList as an empty list, not null. Or you can check the size of list before sending response back with different body.