Angular 6从rest api下载文件

Question

我有我的 REST API，我将我的 pdf 文件放在其中，现在我希望我的 angular 应用程序通过我的网络浏览器点击下载它，但我得到了 HttpErrorResponse

“位置 0 处 JSON 中的意外令牌百分比”

"SyntaxError: JSON.parse 中位置 0↵ 处的 JSON 中的意外标记 % (

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);

}

和调用

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

Answer 1

我通过这种方式解决了这个问题（请注意，我已经合并了在堆栈溢出时找到的多个解决方案，但我找不到引用。请随意将它们添加到 cmets 中）。

在我的服务中，我有：

public getPDF(): Observable<Blob> {   
//const options = { responseType: 'blob' }; there is no use of this
    let uri = '/my/uri';
    // this.http refers to HttpClient. Note here that you cannot use the generic get<Blob> as it does not compile: instead you "choose" the appropriate API in this way.
    return this.http.get(uri, { responseType: 'blob' });
}

在组件中，我有（这是从多个答案合并的部分）：

public showPDF(fileName: string): void {
    this.myService.getPDF()
        .subscribe(x => {
            // It is necessary to create a new blob object with mime-type explicitly set
            // otherwise only Chrome works like it should
            var newBlob = new Blob([x], { type: "application/pdf" });
            
            // IE doesn't allow using a blob object directly as link href
            // instead it is necessary to use msSaveOrOpenBlob
            if (window.navigator && window.navigator.msSaveOrOpenBlob) {
                window.navigator.msSaveOrOpenBlob(newBlob, fileName);
                return;
            }
            
            // For other browsers: 
            // Create a link pointing to the ObjectURL containing the blob.
            const data = window.URL.createObjectURL(newBlob);
            
            var link = document.createElement('a');
            link.href = data;
            link.download = fileName;
            // this is necessary as link.click() does not work on the latest firefox
            link.dispatchEvent(new MouseEvent('click', { bubbles: true, cancelable: true, view: window }));
            
            setTimeout(function () {
                // For Firefox it is necessary to delay revoking the ObjectURL
                window.URL.revokeObjectURL(data);
                link.remove();
            }, 100);
        });
}

以上代码适用于 IE、Edge、Chrome 和 Firefox。但是，我不太喜欢它，因为我的组件是用浏览器特定的东西拉出来的，这些东西肯定会随着时间的推移而改变。

Answer 2

我是这样解决的：

// header.component.ts
this.downloadService.getPdf().subscribe((data) => {

  this.blob = new Blob([data], {type: 'application/pdf'});

  var downloadURL = window.URL.createObjectURL(data);
  var link = document.createElement('a');
  link.href = downloadURL;
  link.download = "help.pdf";
  link.click();

});



//download.service.ts
getPdf() {

  const httpOptions = {
    responseType: 'blob' as 'json')
  };

  return this.http.get(`${this.BASE_URL}/help/pdf`, httpOptions);
}

Answer 3

您可以使用角度指令来做到这一点：

@Directive({
    selector: '[downloadInvoice]',
    exportAs: 'downloadInvoice',
})
export class DownloadInvoiceDirective implements OnDestroy {
    @Input() orderNumber: string;
    private destroy$: Subject<void> = new Subject<void>();
    _loading = false;

    constructor(private ref: ElementRef, private api: Api) {}

    @HostListener('click')
    onClick(): void {
        this._loading = true;
        this.api.downloadInvoice(this.orderNumber)
            .pipe(
                takeUntil(this.destroy$),
                map(response => new Blob([response], { type: 'application/pdf' })),
            )
            .subscribe((pdf: Blob) => {
                this.ref.nativeElement.href = window.URL.createObjectURL(pdf);
                this.ref.nativeElement.click();
            });
    }
    
    // your loading custom class
    @HostBinding('class.btn-loading') get loading() {
        return this._loading;
    }

    ngOnDestroy(): void {
        this.destroy$.next();
        this.destroy$.complete();
    }
}

在模板中：

<a
      downloadInvoice
      [orderNumber]="order.number"
      class="btn-show-invoice"
  >
     Show invoice
  </a>

Answer 4

我的答案是基于@Yennefer 的，但我想使用来自服务器的文件名，因为我的 FE 中没有它。我使用 Content-Disposition 标头来传输它，因为这是浏览器用于直接下载的。

首先，我需要访问请求的标头（注意 get 方法选项对象）：

public getFile(): Observable<HttpResponse<Blob>> {   
    let uri = '/my/uri';
    return this.http.get(uri, { responseType: 'blob', observe: 'response' });
}

接下来，我需要从标题中提取文件名。

public getFileName(res: HttpResponse<any>): string {
    const disposition = res.headers.get('Content-Disposition');
    if (!disposition) {
        // either the disposition was not sent, or is not accessible
        //  (see CORS Access-Control-Expose-Headers)
        return null;
    }
    const utf8FilenameRegex = /filename\*=UTF-8''([\w%\-\.]+)(?:; |$)/;
    const asciiFilenameRegex = /filename=(["'])(.*?[^\\])\1(?:; |$)/;

    let fileName: string = null;
    if (utf8FilenameRegex.test(disposition)) {
      fileName = decodeURIComponent(utf8FilenameRegex.exec(disposition)[1]);
    } else {
      const matches = asciiFilenameRegex.exec(disposition);
      if (matches != null && matches[2]) {
        fileName = matches[2];
      }
    }
    return fileName;
}

此方法检查 ascii 和 utf-8 编码的文件名，首选 utf-8。

一旦我有了文件名，我就可以更新链接对象的下载属性（在@Yennifer 的回答中，即link.download = 'FileName.ext' 和window.navigator.msSaveOrOpenBlob(newBlob, 'FileName.ext'); 行）

关于这段代码的几点说明：

1. Content-Disposition 不在默认的 CORS 白名单中，因此根据您的服务器配置，可能无法从响应对象访问它。如果是这种情况，请在响应服务器中将标头 Access-Control-Expose-Headers 设置为包含 Content-Disposition。

2. 一些浏览器会进一步清理文件名。我的 chrome 版本似乎用下划线替换了 : 和 "。我敢肯定还有其他人，但这超出了范围。

Answer 5

//Step: 1
//Base Service
this.getPDF() {
 return this.http.get(environment.baseUrl + apiUrl, {
      responseType: 'blob',
      headers: new HttpHeaders({
        'Access-Control-Allow-Origin': '*',
        'Authorization': localStorage.getItem('AccessToken') || ''
      })
    });
}

//Step: 2
//downloadService
getReceipt() {
    return new Promise((resolve, reject) => {
      try {
        // {
        const apiName = 'js/getReceipt/type/10/id/2';
        this.getPDF(apiName).subscribe((data) => {
          if (data !== null && data !== undefined) {
            resolve(data);
          } else {
            reject();
          }
        }, (error) => {
          console.log('ERROR STATUS', error.status);
          reject(error);
        });
      } catch (error) {
        reject(error);
      }
    });
  }


//Step 3:
//Component 
getReceipt().subscribe((respect: any) => {
  var downloadURL = window.URL.createObjectURL(data);
  var link = document.createElement(‘a’);
  link.href = downloadURL;
  link.download = “sample.pdf";
  link.click();
});

Answer 6

这也适用于 IE 和 Chrome，几乎相同的答案仅适用于其他浏览器答案有点短。

getPdf(url: string): void {
    this.invoiceService.getPdf(url).subscribe(response => {

      // It is necessary to create a new blob object with mime-type explicitly set
      // otherwise only Chrome works like it should
      const newBlob = new Blob([(response)], { type: 'application/pdf' });

      // IE doesn't allow using a blob object directly as link href
      // instead it is necessary to use msSaveOrOpenBlob
      if (window.navigator && window.navigator.msSaveOrOpenBlob) {
          window.navigator.msSaveOrOpenBlob(newBlob);
          return;
      }

      // For other browsers:
      // Create a link pointing to the ObjectURL containing the blob.
      const downloadURL = URL.createObjectURL(newBlob);
        window.open(downloadURL);
    });
  }