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
