Spring 4 - reject "null" @RequestBody for all endpoints

Question

Jackson deserializes the "null" string as a null request body which is expected (although it would be nice to be able to switch this behaviour off).

The code below triggers validation in case of "{}" payload but not in case of "null" payload. This forces me to do another check for null payload which doesn't seem normal to me since the PayloadValidator could include the null check itself.

@InitBinder
protected void initBinder(WebDataBinder binder) {
  binder.setValidator(new PayloadValidator());
}

@RequestMapping(method = POST, value = "/my/path/here")
public ResponseEntity<String> create(
  @Validated @RequestBody Payload payload
) {
  if (payload == null) {
    // Payload validation logic not in one place 
  }
  // useful work here
}

1. Is there a generic way of rejecting null @RequestBody altogether (i.e. for all endpoints)?
2. If not, can I have all the validation logic in one place and be automatically triggered (i.e. via @Validated or @Valid)?

Thank you, Emanuel

Answer 1

The @RequestBody annotation has an attribute required which is trueby default, so request with an empty body should not work here and the server should respond with an HTTP 400 error.

In this case, a "null" payload effectively means that the request body is not null and that Jackson will deserialize it as a null value. In this case, I don't think that the @Validated validation is triggered, which leaves you with your current arrangement.

As pointed out in your issue, this has been solved with SPR-13176 in Spring Framework 4.2+.