Getting datastore Info through an API

How does one get image data (image url, image info) from datastore through an api?

Is there a tutorial or a project that lets you upload imag开发者_如何学Goes like FotoRatan but also has an api which can be used to get the image and image info from another website?

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Here is an example how to store and serve files (maybe images) using Blobstore: http://code.google.com/appengine/docs/java/blobstore/overview.html#Uploading_a_Blob

You should also look at Picasa Web Albums Data API