c# - 使用 Angular : Unexpected token P in JSON at position 0 at JSON. 解析下载 .xls 文件(<匿名>)

Question

我有以下服务器方法，用于为存储在 Azure Blob Storage 中的 xls 文档返回 byte[]。

[FunctionName("ReadBatchFile")]
        public async static Task<HttpResponseMessage> ReadBatchFile([HttpTrigger(AuthorizationLevel.Function, WebRequestMethods.Http.Get, Route = "Agreements/ReadBatchFile")]HttpRequestMessage req, TraceWriter log)
        {
            try
            {
                var fileName = req.GetQueryNameValuePairs()
                   .FirstOrDefault(q => string.Compare(q.Key, "fileName", true) == 0)
                   .Value;
                var response = new HttpResponseMessage(HttpStatusCode.OK);
                response.Content = new ByteArrayContent(await AzureHelpers.ReadFromBlobStorage(fileName));  //returns byte[] 
                response.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment") { FileName = fileName };
                response.Content.Headers.ContentType =
                    new MediaTypeHeaderValue("application/octet-stream");
                return response;
            }
            catch (Exception ex)
            {
                log.Error(ex.Message);
                req.CreateResponse(HttpStatusCode.InternalServerError);
            }
            return req.CreateResponse(HttpStatusCode.BadRequest);
        }

从上面可以看出，response.Content设置了一个ByteArrayContent，而我的contentType是application/octet -流。

在 Angular 中，我的服务中有以下方法来调用上述函数。

readBatchFile(fileName: string): Observable<Blob> {
    let endpoint = environment.endpoints.agreement.baseUrl + environment.endpoints.agreement.readBatchFile + "&fileName=" + fileName;
    const httpOptions = {
      headers: new HttpHeaders({ contentType: 'application/octet-stream' })}; //application/vnd.ms-excel   application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
    return this.http.get<Blob>(endpoint, httpOptions);
  }

虽然我指定 contentType 是 application/octet-stream，并且我的 get 方法应该返回一个 Blob 类型，我仍然得到以下错误:

Unexpected token P in JSON at position 0↵ at JSON.parse ()

为什么 Angular 仍然将服务器的响应视为 JSON？

更新

这是我的请求 header :

Accept: application/json, text/plain, */*
Authorization: Bearer ...
Origin: http://localhost:4200
Referer: http://localhost:4200/batches
responseType: application/octet-stream
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36

响应头:

Access-Control-Allow-Origin: *
Cache-Control: no-cache
Content-Disposition: attachment; filename=B4debe034-efc6-416f-8082-422a4122a857_MTN_Upgrade_20181017_T065548.xls
Content-Length: 3011
Content-Type: application/octet-stream
Date: Wed, 17 Oct 2018 06:55:48 GMT
Expires: -1
Pragma: no-cache
Server: Microsoft-IIS/10.0
X-Powered-By: ASP.NET

以及响应:

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Answer 1

对于 Angular 8+

return this.http.get(endpoint, { responseType: 'blob'});

return this.http.post(endpoint, postParams, { responseType: 'blob'});

它很微妙，但如果您查看文档，您会注意到 http.post和 http.get不采用 <T> 的通用返回类型当我们设置 responseType: 'blob' .所以我们不需要 <Blob>参与http.get<Blob>了。当您考虑它时，这是有道理的，因为我们告诉 HttpClient 响应的类型是 blob与 responseType: 'blob' .

https://angular.io/api/common/http/HttpClient#post

如果您需要除“blob”之外的其他内容，这里还有其他可用于 responseType 的选项。

responseType: 'arraybuffer' | 'blob' | 'json' | 'text'

https://angular.io/api/common/http/HttpRequest#responseType