[hibernate-dev] JPA Compliance

Chris Cranford chris at hibernate.org
Mon Nov 27 20:06:52 EST 2017 

That seems fine to me.

On 11/27/2017 04:29 PM, Steve Ebersole 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
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>>>>>>>>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>>>>>>>>>>
>>>>>>>>>
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>>>>
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