How to change keys in Objectify

I have a problem. I used to have an entity that had a @id private String key . But now I have to change t开发者_如何学Chat to a @id private Long key. Problem is Objectify wont let me. I get an

IllegalStateException: Loaded Entity has name but com.XX.YYY.MyClass has no String @id

So Im not sure what to do.

---

I'm not up on Objectify (so hopefuly someone who is can step in), but assume that Objectify is passing through the restriction that an Entity key must have exactly one of a name or an id. Once an Entity is created, the key is immutable.

The only ways to re-type a key are

1. Export the data, fix it up outside the datastore, then clear out the datastore and reload, or
2. Create and populate a parallel set of Entities of a new kind, migrating corresponding data from the old entity to the new.

In both case, you have to find and migrate references by hand.

Both of these involve careful work.