我是Angular和Sping Boot 的新手，目前正在做一个涉及上传文件的项目。我已经使用Sping Boot 设置了后端，使用Angular设置了前端，但我遇到了文件上传过程的问题。我用Postman测试了backeend，一切顺利，但与前端的连接不好，它返回500内部服务器错误
这里是一个照片与错误从控制台：
enter image description here
Sping Boot 控制器：

@PostMapping("/upload")
    public ResponseEntity<List<String>> uploadFiles(@RequestParam("files")List<MultipartFile> multipartFiles) throws IOException {
        List<String> filenames = new ArrayList<>();
        for(MultipartFile file : multipartFiles) {
            String filename = StringUtils.cleanPath(file.getOriginalFilename());
            Path fileStorage = get(DIRECTORY, filename).toAbsolutePath().normalize();
            copy(file.getInputStream(), fileStorage, REPLACE_EXISTING);
            filenames.add(filename);
        }
        return ResponseEntity.ok().body(filenames);
    }

字符串
超文本标记语言：

<div class="upload-box">
  <form class="form-inline" method="POST"  enctype="multipart/form-data">
    <div class="form-group">
      <div class="icon">
        <i class="fa-solid fa-2x fa-file-arrow-up"></i>
        <p>Select your PDF file or drop it here</p>
      </div>
      <input class="select" type="file" class="form-control" id="pdfile" placeholder="file" accept="application/pdf" name="pdfFile"(change)="onSelectFile($event)" multiple>
    </div>
    <div class="button">
      <input class="submit" type="submit" value="Upload Pdf" (click)="uploadFile()">
    </div>
    
  </form>
</div>

型
TS：

onSelectFile(event: any): void {
    this.selectedFiles= event.target?.files;

    
  }

  uploadFile()  {
    if (this.selectedFiles.length == 0) {
      console.log('No files selected.');
      return;
    }
    const formData = new FormData();
    for (const file of this.selectedFiles) {
      formData.append('files', file);
    }

    this.dataService.upload(formData).subscribe(
      event => {
        console.log(event);
        this.reportProgress(event);
      },
      error => {
        console.error(error);
      }
    );
  }

型
售后服务：

uploadFile(files: File) {
    const formData = new FormData();
    formData.append('files', files, files.name);
    const httpOptions = {
      headers: new HttpHeaders({
        'Content-Type': 'multipart/form-data'
      })
      
    };

    return this.http.post<any>(this.apiUrl2 + 'file/upload', formData, httpOptions);
  }

型