So to be clear, yes you can post the data from your code to the blobstore, but you are limited by the 1mb request limit.
I've previously posted some sample code in another thread: http://groups.google.com/group/google-appengine-java/browse_thread/thread/2bea1295a3f542de/854ea95dcd986dab -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appeng...@googlegroups.com. To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.