服务通过应用程序引擎的端点API Blob存储图像 [英] serving blobstore image through app-engine endpoints api

问题描述

我建立一个应用程序引擎的端点的API，它需要的画面从用户（Android应用程序），并将其保存到Blob存储编程。然后，我保存在我的数据存储在blob_key。在code是这样的：

I am building an app-engine endpoint api that takes picture from a user (android app) and saves it to blobstore programmatically. Then I save the blob_key in my datastore. The code goes like this:

• 首先，我通过接收到的图像我的 @ endpoint.method 为 messages.BytesField ：

= IMAGE_DATA messages.BytesField（1，必需= TRUE）

image_data = messages.BytesField(1, required=True)

然后，我保存到这样的Blob存储：

Then I save to the blobstore like this:

from google.appengine.api import files

def save_image(data):
  # Create the file
  file_name = files.blobstore.create(mime_type='image/png')

  # Open the file and write to it
  with files.open(file_name, 'a') as f:
    f.write('data')

  # Finalize the file. Do this before attempting to read it.
  files.finalize(file_name)

  # Get the file's blob key
  blob_key = files.blobstore.get_blob_key(file_name)
  return blob_key # which is then saved to datastore

现在我想为图像了。我不知道如何适应以下code到我的终端API：

Now I want to serve the image back. I don't see how to fit the following code into my endpoints api:

from google.appengine.ext import blobstore
from google.appengine.ext.webapp import blobstore_handlers
class ServeHandler(blobstore_handlers.BlobstoreDownloadHandler):
  def get(self, resource):
    resource = str(urllib.unquote(resource))
    blob_info = blobstore.BlobInfo.get(resource)
    self.send_blob(blob_info)

在最后，我想像这样的一个服务程序：

In the end I imagine a serving procedure like this:

• 在@ endpoints.method：

• in @endpoints.method:

获取blob_key从数据存储

get blob_key from datastore

获取图像blob_key

obtain image with blob_key

图像添加到StuffResponseMessage

add image to StuffResponseMessage

发送StuffResponseMessage到前端（Android应用程序）

send StuffResponseMessage to front-end (android app)

我的做法是，因为我要保护我的用户的隐私。就如何做好这一点有什么想法？ 我的code段一般由谷歌开发者教程。

My approach is because I want to protect the privacy of my users. Any thoughts on how to do this well? My code snippets are generally from the google developer tutorial.

编辑：

我不明白我怎么会通过blob_key从数据存储到下面的方法来获取图像：

I don't see how I would pass the blob_key from the datastore to the following method to retrieve the image:

from google.appengine.ext import blobstore
from google.appengine.ext.webapp import blobstore_handlers
class ServeHandler(blobstore_handlers.BlobstoreDownloadHandler):
  def get(self, resource):
    resource = str(urllib.unquote(resource))
    blob_info = blobstore.BlobInfo.get(resource)
    self.send_blob(blob_info)

什么是资源啊？

推荐答案

我相信资源是 BlobKey 对象你想成为，作为字符串，从URL路径retreived什么。如果你看看 google.appengine.ext.blobstore.BlobInfo 的 GET 方法使用功能<$源C $ C> __ normalize_and_convert_keys ，它利用一个参数 BlobKey 对象或字符串。

I believe resource is the BlobKey object of what you want to serve, as a string, retreived from url path. If you look at the source of google.appengine.ext.blobstore.BlobInfo the get method uses a function __normalize_and_convert_keys that takes an argument of BlobKey object OR string.

如果BLOB是图像，也许这是最好送服务的URL，而不是到你的Andr​​oid应用，在 StuffResponseMessage 也许在你的情况。从谷歌的服务的Blob DOC：

If the blob is an image, maybe it's best to send the serving url instead to your Android app, in StuffResponseMessage maybe in your case. From google's Serving a Blob doc:

如果您是服务的图像，更有效的和潜在的较便宜的方法是使用的使用App Engine的图像API，而不是send_blob get_serving_url 。该get_serving_url功能可让您直接服务于图像，而不必通过您的App Engine的实例。

If you are serving images, a more efficient and potentially less-expensive method is to use get_serving_url using the App Engine Images API rather than send_blob. The get_serving_url function lets you serve the image directly, without having to go through your App Engine instances.

因此​​，在你保存图像，拿回来 blob_key （按你的方法 save_image（数据）以上）做一个服务的URL，然后在你的Andr​​oid应用获取图像从返回的URL。这当然意味着暴露的图片网址没有隐私保护。

So after you save the image, take the returned blob_key (as per your method save_image(data) above) to make a serving url, then in your Android app get the image from the returned url. That of course means exposing the image url without privacy protection.

如果你想与保护做到这一点，使用 BlobReader 的类用类似的界面文件中读取的斑点。不能从服务的Blob的例子使用的方法/类，因为你做了 remote.Service 的子类，而不是一个处理程序。

If you want to do it with protection, use BlobReader class to read the blob with file like interface. You can't use the method/class from Serving a Blob example because you do it in a remote.Service subclass rather than a handler.

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