How can I send JSON via HTTP GET and get a status code in return?

Question

I've implemented a GetMapping that takes a RequestBody and returns a status code:

@GetMapping(consumes = "application/json", produces = "application/json")
public ResponseEntity getAgreement(@RequestBody DataObject payload) {
    Boolean found = agreementService.findSingleAgreement(payload);
    if (found) {
        return new ResponseEntity(HttpStatus.OK);
    } else {
        return new ResponseEntity(HttpStatus.NOT_FOUND);
    }
}

I do not want to implement a GetMapping with multiple RequestParams, that's what the JSON's for.

Now I'm having a hard time testing that Get-Request because ResponseEntity either can't be deserialized by Jackson or the RequestBody in HttpEntity is not being read:

@Test
public void testGetRequest() {

    DataObject dataObject = new DataObject();
    dataObject.setAgrType("A"); // more setters exist

    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_JSON);
    HttpEntity<DataObject> entity = new HttpEntity<>(dataObject, headers);

    ResponseEntity<DataObject> answer = this.restTemplate
            .withBasicAuth(username, password)
            .exchange(URL, HttpMethod.GET, entity,
                    new ParameterizedTypeReference<ResponseEntity>() {}); // exhange's causing trouble!!

    assertThat(answer.getStatusCode()).isEqualTo(HttpStatus.OK);
}

Here's the Exception from Jackson:

org.springframework.http.converter.HttpMessageConversionException: Type definition error: [simple type, class org.springframework.http.ResponseEntity]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `org.springframework.http.ResponseEntity` (no Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator) at [Source: (PushbackInputStream); line: 1, column: 2]

Answer 1

@GetMapping is a specialized version of @RequestMapping annotation that acts as a shortcut for @RequestMapping(method = RequestMethod.GET). consumes makes sense for @RequestMapping(method = RequestMethod.POST) (or for the specialized version, @PostMapping) but not for @GetMapping. You need to use HTTP POST to be able to consume your JSON data.