Google App Engine downloadable and not downloadable blob items

i am a newbie in Google Web Toolkit and Google App Engine Technology so i need your help based on blobs. I am developing a web application for a company which needs to upload some files and serve them to their customers. The problem is that when someone uploads an item to the blobstore a url is created and whoever has that link can download/view the file but the specifications are the file to be downloaded to the user who have paid for that. Of course the user should be logged in before. So, how can i have some restrictions to the blob items and make t开发者_JS百科hem private to the prepaid customers?

Thanks in advance, Stefanos Antaris

The problem is that when someone uploads an item to the blobstore a url is created and whoever has that link can download/view the file but the specifications are the file to be downloaded to the user who have paid for that.

That's not the case. The upload URL can only be used to upload the file, not to download it. If you use the image serving API, a URL is generated for your image that anyone can use, but that only happens if you explicitly call that API. Other than that, the only way to download a blob is if your app sets the correct header, as documented here.