[hibernate-dev] JPA Compliance
andrea boriero
andrea at hibernate.org
Tue Nov 28 05:38:24 EST 2017
It is not about the order but about duplicates.
With the following
class A {
List<b> bsl
@JoinTable(name = "A_B",
joinColumns = @JoinColumn(name = "A_ID"),
inverseJoinColumns = @JoinColumn(name = "B_ID"),
)
@ManyToMany
public List<B> getBs() {
return b;
}
}
class *B*{
List<A> as;
....
@ManyToMany(mappedBy = "bs", cascade=CascadeType.ALL)
public List<A> getAs() {
return as;
}
}
and it seems JPA expects the JoinTable A_B to have a PK (A_ID,B_ID).
On 28 November 2017 at 05:44, Vlad Mihalcea <mihalcea.vlad at gmail.com> wrote:
> I don't understand what is the requirement for the @Bag annotation and the
> `hibernate.jpa.compliance=list` setting.
>
> From the JPA spec, only if we provide @OredrBy or @OrderColumn we get an
> ordered List.
> Otherwise, the order is undefined.
> Is there anything I'm missing about handling Lists according to the JPA
> spec?
>
> Vlad
>
> On Mon, Nov 27, 2017 at 11:29 PM, Steve Ebersole <steve at hibernate.org>
> wrote:
>
>> So then how about the following:
>>
>>
>> 1. Add a multi-valued setting to define various categories of JPA
>> compliance. E.g. `hibernate.jpa.compliance` with multi-selectable values
>> such as:
>> 1. query (strict jpql compliance)
>> 2. txn (transaction handling per spec)
>> 3. close (multiple calls to EMF and EM #close methods)
>> 4. list (no bags)
>> 5. others?
>> 6. all (there should be some form of specifying all)
>> 2. Add @Bag as an explicit declaration of a bag, even if
>> `hibernate.jpa.compliance=list` is specified - that setting just
>> controls how List with no @OrderColumn is interpreted. I vote to delay
>> adding that until 6.0
>> 3. Retain current behavior for "double close" calls unless "close"
>> compliance has been specified.
>> 4. Keep current behavior unless "txn" compliance has been specified
>>
>>
>>
>> On Mon, Nov 27, 2017 at 4:54 AM andrea boriero <andrea at hibernate.org>
>> wrote:
>>
>>> On 24 November 2017 at 17:39, Steve Ebersole <steve at hibernate.org>
>>> wrote:
>>>
>>>> Andrea, SF is a EMF. Unwrapping simply returns the same instance.
>>>>
>>>
>>> yes but has you pointed out due to the bootstrapping the behaviour of
>>> the SF will be strict JPA compliant.
>>>
>>>>
>>>> Another thing I was discussing with Andrea in chat is possibly making
>>>> these multi-valued, or having multiple values for this. I can't imagine
>>>> the FQN case is really all that appealing to a user. I'm fairly certain a
>>>> user would rather simply say "yeah, treat transactions according the JPA
>>>> spec" as opposed to "here is a class I will provide that will tell will
>>>> treat transactions according to the JPA spec".
>>>>
>>>> We have started to identify some cases where we deviate from the
>>>> spec[1], such as:
>>>> * Strict query compliance. As I mentioned earlier we do have such a
>>>> setting already for this in particular
>>>> * List versus Bag determination from mappings.
>>>> * Closed EMF (SF) handling
>>>> * EntityTransaction status checking - JPA says we should throw
>>>> exceptions whereas we just ignore the call.
>>>>
>>>> We need to decide also which of these we want to just change outright
>>>> versus controlling via a setting.
>>>>
>>>> * Setting
>>>> * Setting, or introduce a new @Bag annotation - the annotation option
>>>> is actually pretty appealing since often times the bag behavior is so
>>>> unexpected from users...
>>>>
>>>
>>> @Bag seems really a good idea to me but that means changing the current
>>> default behaviour, forcing users to change the code, so not sure if we need
>>> also a setting.
>>>
>>>
>>>> * I think we should just change the behavior of calling EMF#close on a
>>>> closed EMF. Any application that happens to be relying on us no-op'ing
>>>> this call can easily change that to protect the call with an `#isOpen`
>>>> check. In fact I think we should change all of these to match the JPA
>>>> expectations such that it is an error to call any of the following: #close,
>>>> #getCache, #getMetamodel, #getCriteriaBuilder, #getProperties,
>>>> #getPersistenceUnitUtil, #createEntityManager. To me these all seem pretty
>>>> reasonable. And in fact I think we used to handle this all properly from
>>>> the EMF side. I think we just lost that behavior when we changed to have
>>>> our contracts extend the JPA ones since we kept the legacy Hibernate
>>>> behavior in SessionFactory.
>>>>
>>>
>>> I do not like the EMF#close behaviour, probably a prefer a separate
>>> setting for this.
>>>
>>>
>>>> * This one I am very undecided. I can see very valid arguments for
>>>> each.
>>>>
>>>
>>> probably for such case a setting may be a good option.
>>>
>>>>
>>>> [1] we really ought to start keeping a list of these. I have started
>>>> adding them to the migration guide. Just as a list of things we need to
>>>> support configuring or switch to the JPA "way".
>>>>
>>>> On Fri, Nov 17, 2017 at 11:06 AM andrea boriero <andrea at hibernate.org>
>>>> wrote:
>>>>
>>>>> I think for 5.3 it's still fine to rely on isJpaBootstrap may be
>>>>> documenting that a SF obtained from unwrapping an EMF will conform to the
>>>>> JPA spec in term of exceptions.
>>>>>
>>>>> On 16 November 2017 at 21:09, Vlad Mihalcea <mihalcea.vlad at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> When I said multiple modes, I was thinking of defining all these
>>>>>> situations
>>>>>> In some interface which declares methods like:
>>>>>>
>>>>>> boolean throwsExceptionWhenClosingAClosedEMF()
>>>>>>
>>>>>> The interface can have two implementations for Strict JPA and Native
>>>>>> mode.
>>>>>>
>>>>>> However, the setting could take the FQN of the interface
>>>>>> implementation, so
>>>>>> a user can define those compatibility methods according to their
>>>>>> needs.
>>>>>>
>>>>>> E.g. Maybe someone wants the Strict JPA mode but with just 2
>>>>>> differences;
>>>>>>
>>>>>> - don't throw exception when closing the ENG twice
>>>>>> - use the native Hibernate FlushMode.AUTO instead of the JPA one.
>>>>>>
>>>>>> Vlad
>>>>>>
>>>>>> On 16 Nov 2017 10:49 pm, "Steve Ebersole" <steve at hibernate.org>
>>>>>> wrote:
>>>>>>
>>>>>> > There is already a similar setting, although specific to query
>>>>>> language:
>>>>>> > `hibernate.query.jpaql_strict_compliance` - so there is precedence
>>>>>> for
>>>>>> > such a solution.
>>>>>> >
>>>>>> > I'm not sure about the "with multiple modes" aspect though. What
>>>>>> are
>>>>>> > these other enumerated mode values?
>>>>>> >
>>>>>> >
>>>>>> > On Thu, Nov 16, 2017 at 2:15 PM Vlad Mihalcea <
>>>>>> mihalcea.vlad at gmail.com>
>>>>>> > wrote:
>>>>>> >
>>>>>> >> Where the JPA way is questionable, let's add one configuration:
>>>>>> >> hibernate.jpa.compliance with multiple modes:
>>>>>> >>
>>>>>> >> - strict: we do whatever the JPA standard says we should do, like
>>>>>> >> throwing an exception when trying to close the EMF twice
>>>>>> >> - native: we bend the rule where we don't agree with the standard
>>>>>> >>
>>>>>> >> Maybe we should expose all those cases and group them in some
>>>>>> interface
>>>>>> >> to allow the user to customize the level of compliance they need.
>>>>>> >>
>>>>>> >> Vlad
>>>>>> >>
>>>>>> >> On Thu, Nov 16, 2017 at 10:06 PM, Steve Ebersole <
>>>>>> steve at hibernate.org>
>>>>>> >> wrote:
>>>>>> >>
>>>>>> >>> It was added deprecated. Meaning I added it knowing it would go
>>>>>> away
>>>>>> >>> and I wanted to avoid users using it.
>>>>>> >>>
>>>>>> >>> BTW, I am talking about a 5.3 release specifically covering 5.2 +
>>>>>> JPA
>>>>>> >>> 2.2. Yes there is a longer term aspect as well with 6.0 and
>>>>>> beyond.
>>>>>> >>>
>>>>>> >>> Its specifically the "where the JPA way is questionable" aspect I
>>>>>> am
>>>>>> >>> asking about. Like to me, it really never makes sense to throw an
>>>>>> >>> exception when I close something that is already closed. So how
>>>>>> do we
>>>>>> >>> handle cases like this?
>>>>>> >>>
>>>>>> >>>
>>>>>> >>> On Thu, Nov 16, 2017 at 1:51 PM Vlad Mihalcea <
>>>>>> mihalcea.vlad at gmail.com>
>>>>>> >>> wrote:
>>>>>> >>>
>>>>>> >>>> Hi Steve,
>>>>>> >>>>
>>>>>> >>>> I think that for 5.2 was ok to have the isJpaBootstrap method to
>>>>>> avoid
>>>>>> >>>> breaking compatibility for the native bootstrap.
>>>>>> >>>> For 6.0, maybe it's easier if we just align to the JPA spec
>>>>>> where it
>>>>>> >>>> makes sense,
>>>>>> >>>> and only provide a separation where the JPA way is questionable.
>>>>>> >>>>
>>>>>> >>>> I noticed that the isJpaBootstrap method is deprecated. Was it
>>>>>> >>>> intended to be removed in 6.0?
>>>>>> >>>>
>>>>>> >>>> Vlad
>>>>>> >>>>
>>>>>> >>>> On Thu, Nov 16, 2017 at 6:21 PM, Steve Ebersole <
>>>>>> steve at hibernate.org>
>>>>>> >>>> wrote:
>>>>>> >>>>
>>>>>> >>>>> Part of 5.2 was merging the JPA contracts into the corresponding
>>>>>> >>>>> Hibernate
>>>>>> >>>>> ones. So, e.g., we no longer "wrap" a SessionFactory in an
>>>>>> impl of
>>>>>> >>>>> EntityManagerFactory - instead, SessionFactory now extends
>>>>>> >>>>> EntityManagerFactory.
>>>>>> >>>>>
>>>>>> >>>>> This caused a few problems that we handled as they came up. In
>>>>>> >>>>> working on
>>>>>> >>>>> the JPA 2.2 compatibility testing, I see that there are a few
>>>>>> more
>>>>>> >>>>> still
>>>>>> >>>>> that we need to resolve. Mostly they relate to JPA expecting
>>>>>> >>>>> exceptions in
>>>>>> >>>>> certain cases where Hibernate has historically been lenient.
>>>>>> E.g., JPA
>>>>>> >>>>> says that calling EntityManagerFactory#close on an EMF that is
>>>>>> already
>>>>>> >>>>> closed should result in an exception. Historically, calling
>>>>>> >>>>> SessionFactory#close on a SF that is already closed is simply
>>>>>> ignored.
>>>>>> >>>>> Philosophical debates aside[1], we need to decide how we want
>>>>>> to handle
>>>>>> >>>>> this situation such that we can throw the JPA-expected
>>>>>> exceptions when
>>>>>> >>>>> needed. Do we simply change SF#close to match the JPA
>>>>>> expectation?
>>>>>> >>>>> Or do
>>>>>> >>>>> we somehow
>>>>>> >>>>> make SF#close aware of JPA versus "native" use? This latter
>>>>>> option
>>>>>> >>>>> was the
>>>>>> >>>>> intent of `SessionFactoryOptions#isJpaBootstrap` and we can
>>>>>> certainly
>>>>>> >>>>> continue to use that as the basis of the solution here for
>>>>>> other cases.
>>>>>> >>>>>
>>>>>> >>>>> This `#isJpaBootstrap` flag is controlled by the JPA bootstrap
>>>>>> code.
>>>>>> >>>>> So if
>>>>>> >>>>> the EMF is created in either of the 2 JPA-defined bootstrap
>>>>>> mechanisms,
>>>>>> >>>>> that flag is set to true. It's an ok solution, but it does
>>>>>> have some
>>>>>> >>>>> limitations - mainly, there was previously a distinction between
>>>>>> >>>>> SF#close
>>>>>> >>>>> being called versus EMF#close being called (they were different
>>>>>> >>>>> classes, so
>>>>>> >>>>> they could react differently). Therefore, regardless of
>>>>>> bootstrap
>>>>>> >>>>> mechanism, if the user unwrapped the EMF to a SF, they would
>>>>>> always
>>>>>> >>>>> get the
>>>>>> >>>>> legacy SF behavior.
>>>>>> >>>>>
>>>>>> >>>>> So long story short, so we want to consider an alternative
>>>>>> approach to
>>>>>> >>>>> deciding what to do in "some"[2] of these cases? Again, we
>>>>>> clearly
>>>>>> >>>>> need
>>>>>> >>>>> these to throw the spec-mandated exceptions in certain "strict
>>>>>> >>>>> compliance"
>>>>>> >>>>> situations. The question really is how to do that. Should we:
>>>>>> >>>>>
>>>>>> >>>>> 1. just completely change the behavior to align with the
>>>>>> spec?
>>>>>> >>>>> 2. change the behavior to match the spec *conditionally*,
>>>>>> where that
>>>>>> >>>>> condition could be:
>>>>>> >>>>> 1. `#isJpaBootstrap`
>>>>>> >>>>> 2. some setting
>>>>>> >>>>> 3. some extension contract
>>>>>> >>>>> 4. something else?
>>>>>> >>>>
>>>>>> >>>>
>>>>>> >>>>>
>>>>>> >>>>> Thoughts?
>>>>>> >>>>>
>>>>>> >>>>>
>>>>>> >>>>> [1] It's not relevant e.g. that I think JPA is wrong here. We
>>>>>> need to
>>>>>> >>>>> comply with the spec, at least in certain cases ;)
>>>>>> >>>>>
>>>>>> >>>>> [2] I say "some" here, because I think the spec is correct in
>>>>>> some
>>>>>> >>>>> cases -
>>>>>> >>>>> for example, I think its clearly correct that a closed EMF
>>>>>> throws an
>>>>>> >>>>> exception when `#createEntityManager` is called. Personally I
>>>>>> think
>>>>>> >>>>> its
>>>>>> >>>>> questionable whether closing an already closed EMF should be an
>>>>>> >>>>> exception.
>>>>>> >>>>>
>>>>>> >>>> _______________________________________________
>>>>>> >>>>> hibernate-dev mailing list
>>>>>> >>>>> hibernate-dev at lists.jboss.org
>>>>>> >>>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>>>>>> >>>>>
>>>>>> >>>>
>>>>>> >>>>
>>>>>> >>
>>>>>> _______________________________________________
>>>>>> hibernate-dev mailing list
>>>>>> hibernate-dev at lists.jboss.org
>>>>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>>>>>>
>>>>>
>>>>>
>
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