[hibernate-dev] [ORM/OGM] String-typed version properties

[Gunnar Morling]

All,

I'm working on supporting on the CouchDB backend for OGM, and more
specifically on integrating the optimistic locking functionality which is
built into CouchDB [1].

For that purpose, each CouchDB document has a defined field "_rev" which is
a UUID and is updated on the server-side upon each write. So I thought I
could map this attribute like this:

    @Generated //this prop. needs to be read back value after writes
    @Version //this prop. is used for optimistic locking
    String _rev;

But this gave me a CCE since @Version is not allowed on Strings
(org.hibernate.type.StringType is no VersionType).

Looking around, I found BinaryType which looks like what'd I need for
Strings, there is also a note mentioning basically the same use case case
[2]. If I register a custom type derived from StringType with an equivalent
implementation of the VersionType contract, I get the behavior I need.

Does anyone see a problem with making o.h.t.String a VersionType in this
way (i.e. it'd only support DB-generated values)?

Thanks,

--Gunnar

[1] https://hibernate.atlassian.net/browse/OGM-392
[2] "only known application of binary types for versioning is for use with
the TIMESTAMP datatype supported by Sybase and SQL Server, which are
completely db-generated values"