Spring Controller @RequestBody with file upload is it possible?

You can actually simplify your life here since all you are doing is submitting a form that contains some fields and file.
You don’t need @RequestBody for what you are trying to do. You can use regular Spring MVC features, so your controller method would look like:

@ResponseBody
public WebResponse<Boolean> updateEUSettings(
     Locale locale, 
     @Valid EUPSettingsWrapper endUserPortalSettingsWrapper, 
     @RequestParam(value = "file1", required = true) MultipartFile logo
) {


}

The client that submits the request to this controller will need to have a form with enctype="multipart/form-data".

In your Spring MVC test you would write something like this:

getMockMvc().perform(fileUpload(uri).file("file1", "some-content".getBytes()) 
                        .param("someEuSettingsProperty", "someValue")
                        .param("someOtherEuSettingsProperty", "someOtherValue")
                        .accept(MediaType.APPLICATION_JSON)
                        .contentType(MediaType.MULTIPART_FORM_DATA))
                        .andExpect(status().isOk());