title: @Valid does not work when @RequestPart is used in Spring
body: <p><code>@Valid</code> annotation is not calling validator when <code>@RequestPart</code> is used. In other places I used <code>@Valid</code> with <code>@RequestBody</code> and it works fine.
  There is no error just passing the wrong validation also.</p>
  
  <p>Below is the code.</p>
  
  <pre><code>@InitBinder("campaignCreatorDTO")
  public void initCreatorDTOBinder(WebDataBinder binder) {
  
      binder.addValidators(new CreatorDTOValidator());
  }
  
  @PostMapping(value = "/creator", consumes = {"multipart/form-data"}, produces = {"application/json"})
  @ResponseBody
  @ResponseStatus(HttpStatus.CREATED)
  public @Valid
  ResponseDTO creator(@Valid @RequestPart("json") CampaignCreatorDTO campaignCreatorDTO,
                      @RequestPart(name = "file", required = false) MultipartFile adGraphic) {
  }
  </code></pre>