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Personally, I would recommend using the blobstore API for this since it is officially supported by google and means it won't break in the future. It also has nice bindings into the imageservice. http://code.google.com/appengine/docs/java/blobstore/overview.html

I made some code public that does what you describe: it is a simple   cache interface that has implementations for in-memory, memcache and   the datastore.  You get about 100MB of heap space to use which can   significantly speed up your caching. There is also a CompositeCache class that allows you to layer the   caches so that it first checks in-memory, then memcache , then the   datastore.  Puts go to all levels and cache hits refresh the higher   levels.  e.g. if an item is not in-memory and has been flushed from   memcache but is still present in the datastore then the other two will   be updated.

There's a 30 second deadline for web requests, and a 10 second deadline for URLFetch requests. You'll want to make sure you aren't exceeding either of these.

You must have two things in consideration: the appid and version must match, and you should enable datastore writes.

I have an Entity with an id type of Long, and the id gets filled in after I call makePersistent(). Here is what the code looks like:     GameEntity game = new GameEntity();    log.warning("before makePersistent id is " + game.getId());    pm.makePersistent(game);    log.warning("after makePersistent id is " + game.getId()); Here is a snippet of the GameEntity class: @PersistenceCapable(identityType = IdentityType.APPLICATION)public class GameEntity {    @PrimaryKey    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)    private Long id; And the output shows what you'd expect: WARNING 6428 - before makePersistent id is nullWARNING 6444 - after makePersistent id is 6 UPDATE: It occurred to me belatedly that you might want an actual Key object. You can create that yourself if you have the id: public Key getKey() {    return KeyFactory.createKey(GameEntity.class.getSimpleName(), id);}

signed requests will still be redirected. Auth-constraint only applies to Users logged in via the web or OpenID. This is a good feature request, however, and I will bring it up.

That was referring to the bulkloader, which lets you do those things. App Engine's datastore isn't a relational database. We can't do a dump of all your data without iterating through all of your indexes, then retrieving your Entities.

queue.add(     DatastoreServiceFactory.getDatastoreService().getCurrentTransaction(),     TaskOptions.Builder.url("/path/to/my/worker"));