Spring4 #RequestBody required doesn't work - spring

Question

I've upgrade Spring version from 4.0.x to 4.2.3 (4.2.4 just now), suddenly, "required = false" property from #RequestBody annotation does not work as expected (as it did before the version change).
Server response with HttpStatus 415 - Unsupported Media Type.
The controller method (same for every Spring versions).
#RequestMapping(value = "/entity/{entityId}/{from}/{size}", method = RequestMethod.POST)
#ResponseBody
#JsonView(ToShowIn.App.class)
public ResponseEntity<?> getActiveEntityPaged(
#PathVariable int entityId, #PathVariable int from, #PathVariable int size,
#RequestBody(required = false) EntityFilterParam entityFilterParam) {
...
}
Really, it's not problem because from the client, avoiding send null, for example, setting empty EntityFilterParam instance is enough to fix it. But I would like to understand if this bothering issue is because a wrong concept from me or rather is due for a bug from the new Spring versions.
UPDATE#1
Versions
<spring-version>4.2.4.RELEASE</spring-version>
<jackson-2-version>2.3.2</jackson-2-version>
Request is from Android device, working with spring-android library (AKA RestTemplate).
Generic method, works on 4.0.x version, where EntityFilterParam can be null.
super.doRestList(
new HttpEntity<EntityFilterParam>(EntityFilterParam, this.getHttpHeaders()),
HttpMethod.POST,
urlBuilder);
On 4.2.3 and 4.2.4, to fix the issue, EntityFilterParam can't be null. -> HttpStatus 415 - Unsupported Media Type. To fix it.
super.doRestList(
new HttpEntity<EntityFilterParam>((EntityFilterParam != null) ? EntityFilterParam : new EntityFilterParam(), this.getHttpHeaders()),
HttpMethod.POST,
urlBuilder);
Inside doRestList, RestTemplate request is performed.
final ResponseEntity<E[]> responseEntity =
(ResponseEntity) super.getRestTemplate()
.exchange(urlBuilder.getURL(), httpMhetod,
requestEntity, this.entityArray.getClass());
Where, urlBuilder.getURL() (URL string, here #PathVariables are working fine) and this.getHttpHeaders() return the next HttpHeaders configuration.
RestFactory.httpHeaders = new HttpHeaders();
RestFactory.httpHeaders.setAuthorization(this.getAuthorization(user));
RestFactory.httpHeaders.set(HttpHeaders.CONNECTION, "Close"); // Switch off keep-alive.
RestFactory.httpHeaders.set(HttpHeaders.ACCEPT_LANGUAGE, "en-US,en;q=0.8");
RestFactory.httpHeaders.set(HttpHeaders.ACCEPT, MediaType.APPLICATION_JSON_VALUE);
super.getRestTemplate() is the singleton method which returns the RestTemplate instance set with my own CloseableHttpClient configuration.
I know HttpHeaders.CONTENT_TYPE for application/json is missing, but is consciously, in fact, it works when the http body payload is not empty, and fails when it is.
When the error occurs, 415 is performed before the flow of the request goes inside the controller method, therefore, any operation is doesn't performed.
UPDATE#2
Another interesting point, Jackson2 serializes the null value as "null" string, then the body payload is not being null, is filled with "null".

Answer 1

I've tried reproducing this exact issue, without much success.
Do you confirm that with a curl command the problem still exists?
Something like curl -vvv -X POST https://example.com/entity/12/50/10 (if so, paste here the output)
I'm not 100% about this for RestTemplate in spring-android, but if no content type is provided, the template adds by default a "Content-Type: application/x-www-form-urlencoded". If this is the case, configuring a "DEBUG" log level for "org.springframework.web" should show something like
[INFO] [talledLocalContainer] org.springframework.web.HttpMediaTypeNotSupportedException:
Content type 'application/x-www-form-urlencoded' not supported
I think you should set the Content-Type anyway. You mentioned this fails when you do - could you elaborate a bit on that?