title: Google AppEngine Blobstore: Downloading a Blob by Filename in Java
body: <p>Suppose I've uploaded a bunch of files (images in this case, if it matters) to GAE's BlobStore.<br>
  Later, I want to be able to download those files from somewhere else.<br>
  I know that I can use BlobStoreService's serve method to grab a blob by BlobKey, but how do I get the blobkey associated with a given filename?<br>
  I can't seem to find any built-in functionality for this.</p>