2018-05-31 19:59 GMT+02:00 Lyor Goldstein <lgoldst...@apache.org>: > >>> > I disagree with the characterization that they do not have a "real > concept > > behind them" they represent contracts of entities that have similar > > attributes. IMO, all the various *XxxHolder*(s) represent an entity that > > provides whatever these "attribute" interfaces hold. > > >>> Well, I would agree on this principle in theory. > However, I've seen no evidence throughout the code that this is actually > useful. > > Here is something that I see as a useful consequence of these "marker" > interfaces - some degree of standardization: e.g., if more than 1 entity > displays the same "behavior" and/or "attributes", it makes sense to call > them by some standard name - e.g., avoid *getSession, getClientSession, > getCurrentSession, getEstablishedSession* in different entities that > basically expose a *ClientSession*. To me it is another aspect of the > D.R.Y. principle since it makes it easier to search for code that refers to > a known entity knowing that it will use a standard way to expose it. >
I fully understand that it's the reason why they have been introduced. But I think that's somewhat wrong. The most obvious example to me is the SessionHolder / ClientSessionHolder / ServerSessionHolder or the NamedResource#getName. Those are actually never used (on the interface), because almost every time when the method is used, it's inside the class implementation itself, so the interface is not used. I actually found the use of the interface very annoying because whenever I want to find where the getSession() is used, I end up with *all* references to the SessionHolder, so basically, all calls to getSession() in the whole code base. That make search for method usage quite useless. -- ------------------------ Guillaume Nodet
