For the record, I agree with what Tony has said. It's usually better to @CommitAfter on a page action or on a service rather than a low level DAO.
That being said, I think your problem is annotating the interface instead of the concrete class. Prior to recent 5.4 builds, annotations were not copied from interface to service. Thiago has fixed this recently and if you upgrade to 5.4 beta you can annotate the interface.