N.B. that chancing the exception types thrown by our native methods is an API change in my opinion.
So while I think you can have some Hibernate exceptions now extend some of the types expected by JPA, a fully "clean room" approach is not something I'd do in a minor release. On 25 April 2016 at 15:25, Steve Ebersole <st...@hibernate.org> wrote: > I agree with Gunnar in that the underlying question here is in how we see > the "Hibernate API" long term. However I would consider the following > categories: > > Methods which are Hibernate-only > Methods which Hibernate had historically which share a signature with JPA > Methods which we added to Hibernate specifically for JPA. > > > Personally, in retrospect, I would say that group (3) unequivocally should > have been handled by just throwing the JPA exceptions. In a clean-room impl > that's what I would do. > > So I guess the question is whether we want to look at this as a clean-room > impl or if we want to constrain ourselves to the legacy exception types. I > do wonder if a hybrid approach may be the best, as touched on before. > Namely, where JPA expects an IllegalArgumentException, > IllegalStateException, etc we throw those; for the rest we'd have Hibernate > exception extend PersistenceException. I think that's a great compromise. > > I'd also mention that in the IllegalArgumentException, > IllegalStateException, etc cases there are a few places where > HibernateExceptions cover the JPA case already. E.g. JPA says that if there > is a problem with the JPQL query (String) used to create a Query an > IllegalArgumentException should be thrown; Hibernate currently handles this > by throwing a QuerySyntaxException - we could just make QuerySyntaxException > extend from IllegalArgumentException rather than Hibernate's > HibernateException hierarchy. > > I think the bottom line is that having Session and EntityManager split > before caused all kinds of difficult-to-debug complexity that I'd rather > avoid as we consolidate them together. > > > On Mon, Apr 25, 2016 at 5:37 AM Sanne Grinovero <sa...@hibernate.org> wrote: >> >> Gunnar's words seem wise to me: users will need to have the JPA API on >> classpath anyway, so I don't see why we should have - and maintain - >> strategies for different kind of exceptions. >> >> This might have been useful in the past, but looking forward? >> >> If the reasoning is that Hibernate - having more features - could >> throw more specific and informative exceptions, we could have some >> Hibernate exceptions to subclass the JPA ones? >> >> Would be nice to avoid breaking the expected exception types in a >> minor, so I'm not sure if you can do that in all cases by subclassing >> the JPA ones, but I suspect it can get you a long way. >> >> >> On 25 April 2016 at 10:13, Gunnar Morling <gun...@hibernate.org> wrote: >> > The strategy approach sounds nice on first thought, but it also adds >> > complexity. >> > >> > I think the underlying question is: What's the long-term strategy around >> > the "Classic API"? Should it remain in place for all times as a complete >> > alternative to the JPA API? >> > >> > Or should we begin to deprecate it and narrow it down in favour of the >> > corresponding functionality standardized in JPA, and only functionality >> > not >> > present in JPA would be exposed through some kind of unwrap()? >> > >> > Without having thought about all the implications too much, I'd lean >> > towards the latter, in which case I vote for "1. Just move to JPA >> > expected >> > exceptions" as part of such larger effort. >> > >> > It'd be interesting to run a poll to see some figures of people using >> > classic vs. JPA. >> > >> > --Gunnar >> > >> > >> > >> > 2016-04-25 10:47 GMT+02:00 andrea boriero <and...@hibernate.org>: >> > >> >> Having a Strategy gives us more flexibility so +1. >> >> >> >> About the expectations I think what Vlad says is reasonable. >> >> >> >> On 25 April 2016 at 06:04, Vlad Mihalcea <mihalcea.v...@gmail.com> >> >> wrote: >> >> >> >> > Your second email summarizes my thoughts as well. If we can separate >> >> > the >> >> > exception handling in two separate strategies that are defined during >> >> > bootstrap (JPA vs Hibernate), >> >> > I think that's the way to go. >> >> > >> >> > There so many projects out there that rely on the exception type >> >> > being >> >> > thrown, and changing those would make it very difficult for them to >> >> migrate >> >> > to this new version. >> >> > But that only affects Hibernate-native projects since, for those who >> >> > have >> >> > been using JPA, they already expect the JPA exceptions anyway. >> >> > >> >> > As for the other behavior discrepancies: >> >> > >> >> > 1. "calling EntityManager#close on a closed EntityManager should >> >> > result >> >> in >> >> > an >> >> > exception;" - that's a reasonable default and shouldn't cause too >> >> > much >> >> > trouble. >> >> > 2. "Another change in expectation is in regards to operations outside >> >> > of >> >> a >> >> > transaction" - in JPA we can execute queries outside a transaction, >> >> > but >> >> any >> >> > write will fail if there is no transactional context, which is >> >> > reasonable >> >> > for me too. If Hibernate allows writes outside of a transactional >> >> context, >> >> > that's definitely a thing we should not support anyway. >> >> > 3. "Asking a Session if is contains (Session/EntityManager#contains) >> >> > a >> >> > non-entity" - we can handle this with the separate exception handler >> >> > strategies to retain both JPA and Hibernate behaviors. >> >> > 4. "Accessing Session/EntityManager#getTransaction. JPA says that is >> >> > only allowed >> >> > for JDBC transactions. Hibernate always allows it." - I'd choose the >> >> > Hibernate behavior because I don;t see how it can cause any issue and >> >> it's >> >> > an enhancement as well. >> >> > >> >> > Vlad >> >> > >> >> > >> >> > >> >> > >> >> > >> >> > On Sat, Apr 23, 2016 at 5:29 PM, Steve Ebersole <st...@hibernate.org> >> >> > wrote: >> >> > >> >> > > Just realized that I should have mentioned an important plan that >> >> > > helps >> >> > > understand the idea behind the "exception handling strategy" route. >> >> > > I >> >> > plan >> >> > > to keep track of how a SessionFactory was bootstrapped in some >> >> > > fashion. >> >> > So >> >> > > when it was bootstrapped from EntityManagerFactoryBuilder (which >> >> > > JPA >> >> > > bootstrap methods leverage) we'd select the "JPA exception >> >> > > handling" >> >> > > strategy impl. When not, we'd use the "legacy Hibernate exception >> >> > > handling" strategy. >> >> > > >> >> > > On Sat, Apr 23, 2016 at 9:21 AM Steve Ebersole >> >> > > <st...@hibernate.org> >> >> > > wrote: >> >> > > >> >> > > > There are a number of "expectation changes" that come about from >> >> > > > consolidating hibernate-entitymanger into hibernate-core. Some >> >> > > > we >> >> have >> >> > > > discussed; some we have not. Hopefully we can come to a >> >> > > > consensus >> >> > > regards >> >> > > > how to deal with these changes... >> >> > > > >> >> > > > The first one is different exception types. We have discussed >> >> > > > this >> >> > > > before. For now, in an effort to fix test failures and move >> >> > > > forward >> >> > with >> >> > > > developing, I simply changed failing tests to expect the JPA >> >> > > > defined >> >> > > > exceptions. I had mentioned, where possible, to to throw a >> >> combination >> >> > > of >> >> > > > the 2 expected exceptions. Generally this falls into 2 discrete >> >> > > categories: >> >> > > > >> >> > > > >> >> > > > 1. JPA expects a PersistenceException and we have historically >> >> > thrown >> >> > > > a HibernateException >> >> > > > 2. JPA expects some form of JDK RuntimeException >> >> > > > (IllegalArgumentException, IllegalStateException, etc) and we >> >> > > > have >> >> > > > historically thrown a HibernateException >> >> > > > >> >> > > > It is unfortunate that Java does not allow exceptions to be >> >> > > > defined >> >> by >> >> > > > means of interfaces; that's the only "clean" way I see to do this >> >> > > > - >> >> > that >> >> > > > would have allowed us to define concrete exception classes that >> >> extend >> >> > > > PersistenceException, IllegalArgumentException, etc and that >> >> implement >> >> > > HibernateException. >> >> > > > >> >> > > > >> >> > > > So I see 3 potential solutions (feel free to bring up others). >> >> > > > >> >> > > > 1. Just move to JPA expected exceptions. >> >> > > > 2. Have HibernateException extend PersistenceException and >> >> > > > just >> >> not >> >> > > > worry about the change in expectation in regards to that >> >> > > > second >> >> > > category. >> >> > > > 3. Push exception handling behind a strategy. This would have >> >> > > > to >> >> > be a >> >> > > > pretty specific strategy for very specific cases. >> >> > > > >> >> > > > The first and second options are pretty self-explanatory and >> >> > > > straight-forward so I won't go into detail there. Just realize >> >> > > > that >> >> > > these >> >> > > > change the expectation for the user. They'd have to change their >> >> code >> >> > to >> >> > > > catch these JPA-defined exceptions. >> >> > > > The other option, I see, is to h >> >> > > > >> >> > > > The third option is perfect in theory, but it is very tedious. >> >> > > > For >> >> > > > example, take the case of trying to perform some operation on a >> >> closed >> >> > > > Session/EntityManager. Hibernate historically threw a >> >> > HibernateException >> >> > > > here. JPA says that should result in an IllegalStateException. >> >> > > > So >> >> in >> >> > > > SessionImpl#checkOpen, when the Session/EntityManager is closed, >> >> > > > we'd >> >> > > > call out to the strategy to handle that condition. Even more, >> >> > Hibernate >> >> > > > (historically) and JPA disagree about which methods getting >> >> > > > called >> >> on a >> >> > > > closed Session/EntityManager should lead to an exception. For >> >> example, >> >> > > > JPA says calling EntityManager#close on a closed EntityManager >> >> > > > should >> >> > > > result in an exception; Hibernate historically did not care if >> >> > > > you >> >> > called >> >> > > > Session#close on a closed Session. So that is a special case, >> >> > > > and >> >> > every >> >> > > > one of those special cases would have to be exposed and handled >> >> > > > in >> >> the >> >> > > > exception handling strategy in additional to the general cases. >> >> > > > >> >> > > > Another change in expectation is in regards to operations outside >> >> > > > of >> >> a >> >> > > > transaction, which I consider a questionable pattern anyway. >> >> Hibernate >> >> > > > historically allowed that; JPA explicitly disallows it. In a way >> >> this >> >> > > > could fall under the exception discussion above, meaning we could >> >> push >> >> > > that >> >> > > > distinction behind the exception handling strategy. Or we could >> >> decide >> >> > > > that we are going to stop supporting that. >> >> > > > >> >> > > > There are a lot of other highly questionable things I have seen >> >> > > > in >> >> the >> >> > > > tests that JPA explicitly disallows that I think we ought to just >> >> stop >> >> > > > supporting and opt for the JPA way, although I am open to >> >> > > > discussing >> >> > them >> >> > > > if any feels strongly about them. Some of these include: >> >> > > > >> >> > > > - Asking a Session if is contains >> >> (Session/EntityManager#contains) a >> >> > > > non-entity. Hibernate historically would just return false. >> >> > > > JPA >> >> > > states >> >> > > > that should be an exception. >> >> > > > - Accessing Session/EntityManager#getTransaction. JPA says >> >> > > > that >> >> is >> >> > > > only allowed for JDBC transactions. Hibernate always allows >> >> > > > it. >> >> > > > >> >> > > > If we go the route of an "exception handling strategy" a lot of >> >> > > > the >> >> > other >> >> > > > points I mentioned above could just be pushed behind that >> >> > > > strategy. >> >> > But >> >> > > I >> >> > > > really want to start looking critically at what we support today >> >> > > > that >> >> > we >> >> > > > maybe really should not be. >> >> > > > >> >> > > _______________________________________________ >> >> > > hibernate-dev mailing list >> >> > > hibernate-dev@lists.jboss.org >> >> > > https://lists.jboss.org/mailman/listinfo/hibernate-dev >> >> > > >> >> > _______________________________________________ >> >> > hibernate-dev mailing list >> >> > hibernate-dev@lists.jboss.org >> >> > https://lists.jboss.org/mailman/listinfo/hibernate-dev >> >> > >> >> _______________________________________________ >> >> hibernate-dev mailing list >> >> hibernate-dev@lists.jboss.org >> >> https://lists.jboss.org/mailman/listinfo/hibernate-dev >> >> >> > _______________________________________________ >> > hibernate-dev mailing list >> > hibernate-dev@lists.jboss.org >> > https://lists.jboss.org/mailman/listinfo/hibernate-dev >> _______________________________________________ >> hibernate-dev mailing list >> hibernate-dev@lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/hibernate-dev _______________________________________________ hibernate-dev mailing list hibernate-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev
