Mock the @ModelAttribute in the request handler of spring controller without using request paramter approach

Question

I need to mock the @ModelAttribute in the request handler of spring controller. I hope to pass diverse values via mock instead of passsing it via MockMVC request parameter. There is a request interceptor which works and possibly is nullyfying even the model object attribute is paased via request parameter hence this question.

So below is the partial code snippet; Componet1: Controller whose request handler's @ModelAtrribute is to be mocked.

@Controller public class MyController { /** some code here*/

@RequestMapping(path = "/myRequest", method = RequestMethod.POST)
@ResponseBody
public String requestHanderForMyRequest(HttpServletRequest request, @ModelAttribute(name="myBean") People person) {
    ...
    Date birthDate = person.getBirthDate();
    ...
    // do something with date
    /** prepare JSON response and return */
    return "{ ...}";
}

}

Component 2: DateFieldInterceptor.java Intercepts date field in request and processes it and then updates it if success flow otherwise resets to null.

Component 3: Mock test method in JUnit test class

@Test
public void testRequestHanderForMyRequest() {
    try {
        ResponseInstance responseInstance = testUtility .loadResponseFromFile("testFile.json");

        Assert.assertNotNull("No base data", responseInstance);

        MvcResult resultantMvc = mockMvc.perform(post("/myRequest")
                                                    .session(mockHttpSession)
                                                .param(START_DATE, START_DATE_VALUE)
                                                .param("birthdate", BIRTH_DATE_VALUE)
                                                .param("personName", "dfs edfsd")
                                                )
                                        .andExpect(status().isOk())
                                        .andExpect(jsonPath("$").exists())
                                        .andExpect(jsonPath("$").isNotEmpty())
                                        .andExpect(jsonPath("$", Matchers.hasKey(PAYLOAD)))
                                        .andExpect(jsonPath("$.*", Matchers.hasSize(1)))
                                        .andExpect(jsonPath(JSON_PATH_ROOT_PAYLOAD).isArray())
                                        .andExpect(jsonPath(JSON_PATH_ROOT_PAYLOAD).isNotEmpty())
                                        .andReturn();
        Assert.assertNotNull(MVC_RESULT_IS_MISSING_FOR_THE_REQUEST, resultantMvc);

        String payloadData = resultantMvc.getResponse().getContentAsString();

        Assert.assertTrue(RESPONSE_IS_MISSING_PAYLOAD_DATA, StringUtils.isNotBlank(payloadData));
    } catch (Exception e) {
        Assert.fail(e.getMessage());
    }
}

The date interceptor is somehow going to negative flow and resetting the date field to null. I wish to unit test the birthdate field of People instance. If I can somehow mock the person.getBirthDate() then I should be alright with the unit test. But mocks don't seem to work for @ModelAttribute parameters.