while making exchange call trying to store multipart file response in an "ResponseEntity<Response<T>> ResponseEntity", here responseEntity is NULL

Question

    **For this method is to create a file, inside this we are calling upload method:**
    ```public ResponseHolder<File> createFile(String id, java.io.File multipartFile) throws Exception {
            // TODO Auto-generated method stub POST /resources/{id}/file
            logger.info("Entered create File: "+multipartFile.getName());
            //validate(id, multipartFile);
            ResponseHolder<File> responseHolder;
            String url = new StringBuilder(SUB_URL).append(id).append("/file").toString();;
            responseHolder = focisService.upload(url, multipartFile, HttpMethod.POST,
                    File.class, focisService.getAuthToken());
            logger.info("Exiting create");
            return responseHolder;
        
        }
    ```
    *------------------------------------------------------------------------------------------------*
    **This upload method, so in this method i m trying to store multipart file response in an object but  i have checked in debug mode the response "ResponceEntity" is null.**
    
  ```  public <T extends GenericModel> ResponseHolder<T> upload( String url, File request, HttpMethod httpMethod,
                Class<T> responseType,
                AuthToken authToken )
        {
            String requestName = "";
    
            if ( logger.isTraceEnabled() )
            {
                if ( request == null )
                {
                    requestName = null;
                }
                else
                {
                    requestName = request.toString();
                }
                logger.trace("exchange: " + url + " : " + " : " + requestName + " : " + httpMethod.toString() + " : "
                        + responseType.toString());
            }
    
            ResponseHolder<T> responseHolder = new ResponseHolder<>();
            Response<T> response = null;
            HttpEntity<LinkedMultiValueMap<String, Object>> requestEntity = getUploadRequestEntity(authToken, request);
    
            @SuppressWarnings("unchecked")
            ParameterizedTypeReference<Response<T>> typeDef = typeMap.get(responseType);
    
            ResponseEntity<Response<T>> responseEntity = null;
    
            logger.info("requestEntity in upload():" + requestEntity);
            if ( null == requestEntity )
            {
                responseHolder.setStatusCode(HttpStatus.UNAUTHORIZED);
                return responseHolder;
            }
    
            try
            {
                try
                {
        responseEntity = restOperations.exchange(getUrl(url), httpMethod, requestEntity, typeDef);
    
                }
                catch ( HttpClientErrorException e )
                {
                    throw e;
                }

no comments ``` ---------------------------------------------------------------------------------------------- ** In console getting this error("400 Bad Request")** 400 Bad Requestenter code here

Bad Request

Your browser sent a request that this server could not understand.

enter code here ] | 400 Bad Request: [ no comments while making exchange call trying to store multipart file response in an "ResponseEntity<Response> ResponseEntity", here responseEntity is NULL ---------------------------------------------------------------------------------------- Where i have to make changes to get proper response