如何使用angular4 rest API和spring-boot上传文件

Question

我使用spring为后端部分实现了这部分代码

@PostMapping("/upload")
public ResponseEntity<String> handleFileUpload(@RequestParam("file") MultipartFile file) {
        String message = "";
        try {
            sp.store(file);
            files.add(file.getOriginalFilename());

            message = "You successfully uploaded " + file.getOriginalFilename() + "!";
            return ResponseEntity.status(HttpStatus.OK).body(message);
        } catch (Exception e) {
            message = "FAIL to upload " + file.getOriginalFilename() + "!";
            return ResponseEntity.status(HttpStatus.EXPECTATION_FAILED).body(message);
        }
    }

并且角度部分我有这个用于前端但是我在hhtpRequest / post中有错误

pushFileToStorage(file: File): Observable<HttpEvent<{}>> {
    let formdata: FormData = new FormData();
    formdata.append('file', file);

    const req = new HttpRequest('POST', '/post', formdata, {
      reportProgress: true,
      responseType: 'text'
    });




    return this.http.request(req);
  }