GAE: how can I combine a BlobstoreUploadHandler and a RequestHandler in 1 webpage

Question

I am making a mailing app in Python on the Google App Engine.

I want to enable an attachment upload (which posts to a BlobstoreUploadHandler) in a 'normal' webpage (posting to a RequestHandler).

If the user has filled part of the 'normal' form, how can I preserve those values after the user has uploaded his (or her) attachment (other then copying all the fields with javascript before submitting the post)?

Answer 1

You can write a request handler that derives from two classes:

class YourRequestHandler(BlobstoreUploadHandler, RequestHandler):
    pass

I also tried this with webapp2's RequestHandlers and it works.

P.S.: In order to prevent orphaned blobs because the user uploaded more files than your application expects (this can easily happen as you have no control over the user's browser), I suggest to write your post handler along the following lines:

def post(self):
    uploads = self.get_uploads()
    try:
        pass  # Put your application-specific code here.
        # As soon as you have stored a blob key in the database (using a transaction),
        # remove the corresponding upload from the uploads array.
    finally:
        keys = [upload.key() for upload in uploads]
        blobstore.delete_multi(keys)