Vaadin-upload:415 unsupported media type while uploading csv file using vaadin upload

Question

I am using Vaadin upload web component https://vaadin.com/elements/vaadin-upload to upload a CSV file from front end after uploading csv file using vaadin upload i am getting 500 internal server error the vaadin upload component is

<vaadin-upload id="calibration"
target="/imdex/idp/api/v1/upload"
method="POST"
timeout=15000
on-upload-start="uploadStarted" >
<iron-icon slot="drop-label-icon" icon="description"></iron-icon>
<span slot="drop-label">Drop your calibration file</span>
</vaadin-upload>

I checked in the header multipart/form data is getting appended to the header, I have checked my server side code from postman i able to send csv file through postman to server side, but the same is not happening from UI. Can anyone help me i am unable to figure out ?

The server side code is :

@RestController
@RequestMapping("imdex/idp/api/v1")
public class BlobstoreController {
@Autowired
BlobstoreService objectStoreService;

@RequestMapping(value = "/upload", method = RequestMethod.POST)
 public @ResponseBody String singleSave(@RequestParam("file") MultipartFile 
file) throws Exception {

 System.out.println("in  upload");

  if (file != null) {
 S3Object obj = new S3Object();
  try {
 obj.setKey(file.getOriginalFilename());
 obj.setObjectContent(file.getInputStream());

  objectStoreService.put(obj);

  } catch (Exception e) {

  throw e;
   } finally {
  obj.close();
  }
  }
  return "uploaded successfully";
  }