Typescript Angular 6从rest api下载文件

我有我的REST API，我把我的pdf文件放在那里，现在我想我的angular应用程序通过我的web浏览器点击下载它，但我得到了HttpErrorResponse

"JSON中位置0处的意外标记%

"SyntaxError:JSON中位于位置0的意外标记%↵ 在JSON.解析(

这是我的终点

    @GetMapping("/help/pdf2")
public ResponseEntity<InputStreamResource> getPdf2(){

    Resource resource = new ClassPathResource("/pdf-sample.pdf");
    long r = 0;
    InputStream is=null;

    try {
        is = resource.getInputStream();
        r = resource.contentLength();
    } catch (IOException e) {
        e.printStackTrace();
    }

        return ResponseEntity.ok().contentLength(r)
                .contentType(MediaType.parseMediaType("application/pdf"))
                .body(new InputStreamResource(is));

}

这是我的服务

  getPdf() {

this.authKey = localStorage.getItem('jwt_token');

const httpOptions = {
  headers: new HttpHeaders({
    'Content-Type':  'application/pdf',
    'Authorization' : this.authKey,
    responseType : 'blob',
    Accept : 'application/pdf',
    observe : 'response'
  })
};
return this.http
  .get("http://localhost:9989/api/download/help/pdf2", httpOptions);

}

和召唤

this.downloadService.getPdf()
  .subscribe((resultBlob: Blob) => {
  var downloadURL = URL.createObjectURL(resultBlob);
  window.open(downloadURL);});