App Engine Blobstore回调未被调用并返回302

Question

我正在尝试在Google App Engine上创建一个REST API，允许将视频上传到Blobstore。在我的本地开发服务器上一切正常，但在部署到GAE时失败。在GAE上它存储视频，但不调用我的回调URL。相反，它返回302，其中位置标头设置为我的回调URL。我尝试从我的客户端手动访问回调URL，但GAE然后抛出异常：java.lang.IllegalStateException: Must be called from a blob upload callback request。我正在使用Spring MVC。

客户端上传代码：

/**
 * URL has been generated by going to /game/{gameId}/video
 */
private void uploadVideo(String uploadUrl) throws Exception {
    HttpClient httpClient = new DefaultHttpClient();
    httpClient.getParams().setBooleanParameter(ClientPNames.HANDLE_REDIRECTS, false);
    HttpPost post = new HttpPost(uploadUrl);
    MultipartEntity mp = new MultipartEntity();
    File video = new File("src/test/resources/video.mp4");
    assertTrue("Couldn't find video file.", video.exists());
    mp.addPart("video", new FileBody(video));
    post.setEntity(mp);
    HttpResponse resp = httpClient.execute(post);
    //Getting 302 here.
    assertEquals("Unexpected HTTP status code.", 200, resp.getStatusLine().getStatusCode());
}

服务器代码：

private BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService();

/**
 * Create a video entity and generate an upload URL.
 */
@RequestMapping(value = "/game/{gameId}/video", method=RequestMethod.POST)
@ResponseBody
public VideoMeta createVideo(@PathVariable Long gameId, @RequestBody VideoMeta meta, Principal auth) {
    //Omitted authentication and video creation logic

    //Get blobstore upload URL.  Callback is /video/{videoId}/blob.
    String uploadUrl = blobstoreService.createUploadUrl("/video/" + video.getId() + "/blob");

    //Create response
    VideoMeta videoMeta = new VideoMeta();
    videoMeta.setVideoId(video.getId());
    videoMeta.setUploadUrl(uploadUrl);
    return videoMeta;
}


/**
 * This method is never called on GAE!
 */
@RequestMapping(value = "/video/{videoId}/blob", method=RequestMethod.POST)
@ResponseBody
public VideoMeta uploadVideo(@PathVariable Long videoId, HttpServletRequest req) {
    Map<String, List<BlobKey>> blobs = blobstoreService.getUploads(req);
    List<BlobKey> blobKeys = blobs.get("video");
    blobstoreService.getByteRange(req);

    int numBlobs = blobKeys.size();
    if(numBlobs != 1) {
        throw new RestException(HttpServletResponse.SC_NOT_ACCEPTABLE, "You should upload exactly one blob.");
    }
    BlobKey blobKey = blobKeys.get(0);

    //Omitted video update logic

    VideoMeta videoMeta = new VideoMeta();
    videoMeta.setVideoId(video.getId());
    return videoMeta;
}