I'm trying to send an image file from Android retrofit2 to a spring server, but I couldn't work on it, so I'm posting a questioncrying

public static insertPromoteMsg insertPromoteMsgAPI() {
        return (insertPromoteMsg) retrofit(insertPromoteMsg.class);
    }

    public interface insertPromoteMsg {
        @Multipart
        @POST("/insertPromoteMsgApp3.do")
        Call<ResponseCode> insertPromoteMsg(@Part MultipartBody.Part uploadFile);
    }

private void insertPromote(EditText writingArea, EditText promoteTitle) {
        File file = new File(imgPath);
        RequestBody requestFile = RequestBody.create(MediaType.parse("multipart/form-data"), file);
        MultipartBody.Part uploadFile = MultipartBody.Part.createFormData("file", file.getName(), requestFile);
        Log.i("test", "insertPromote: "+ file.getName());
        Log.i("test", "insertPromote: "+ requestFile.contentType());
        Log.i("test", "insertPromote: "+ uploadFile.body());
        Call<ResponseCode> call = NetworkService.insertPromoteMsgAPI().insertPromoteMsg(uploadFile);
        call.enqueue(new Callback<ResponseCode>(){
            @Override
            public void onResponse(Call<ResponseCode> call, Response<ResponseCode> response) {
                if(response.isSuccessful()){
                }else{
                }
            }

            @Override
            public void onFailure(Call<ResponseCode> call, Throwable t) {
                Log.i("test", "onFailure: "+t.getMessage());
            }
        });
    }

    @RequestMapping(value = "insertPromoteMsgApp.do", method = RequestMethod.POST)
    @ResponseBody
    public int insertPromoteMsgApp(MultipartFile uploadFile) {
        System.out.println ("insertPromoteMsgApp call");
        if(uploadFile == null) {
            System.out.println("null");
        }else {
            System.out.println(uploadFile.getContentType());
        }
        return 101;
    }