I'm migrating a project from JPA 1 to JPA 2 and I want to use derived identifiers, but I heard Gavin King say that he doesn't like them and even called them garbage, but I didn't see any explanation from him about why he thinks this way. So I thought that was prudent before moving on to ask: are derived identifiers a bad thing? If so, what are the reasons for that?
PS.: I'm not sure if it was Gavin King that called derived identifiers garbage. Maybe it was Steve Ebersole.