[hibernate-dev] Another @Access quandry
Sanne Grinovero
sanne at hibernate.org
Wed Mar 26 14:42:09 EDT 2014
On 26 March 2014 18:37, Steve Ebersole <steve at hibernate.org> wrote:
> My point is that I do not find annotating a getter method with
> @Access(FIELD) to be inherently common sense. It really boils down to the
> purpose/intent of @Access. If @Access *at the attribute level* is
> ultimately *just* indicating how to extract/inject then I think
> @Access(FIELD) on the getter does make sense. If @Access *at the attribute
> level* also directs where to look for annotations (consistent with @Access
> at class/hierarchy-level) then I think @AccessFile needs to be on the field
> along with the other annotations, assuming we stay with non-mixed placement
> for an attribute.
Here a use case: as convention the team likes to put all annotations
on getters, but then for some specific reason a field needs to be
configured to have the ORM to use field access.
Seems fair enough?
Sanne
>
> So let's decide that first. Since the spec does not say clearly one way or
> the other, I guess we have some leeway here.
>
> https://hibernate.atlassian.net/browse/HHH-9085 (Introduce @IdGetter and
> @IdSetter) plays in here as well.
>
>
>
> On Wed, Mar 26, 2014 at 11:21 AM, Emmanuel Bernard <emmanuel at hibernate.org>
> wrote:
>>
>> My take on the spec as always been that I'd rather follow the intent,
>> the common sense above the letter. Likewise, I favored user experience
>> over spec strict adherence.
>> I did clash numerous time with the TCK in these targets but I still
>> prefer that over just doing something stupid but spec to the letter.
>> (this is general and not specific to that case).
>>
>> Anyway so my take is pretty much as it was when I first implemented
>> @AccessType even if it steps over the spec at the margin.
>> BTW I'm also happy if we all decide I made a usability mistake that should
>> be fixed.
>>
>> Emmanuel
>>
>> On Wed 2014-03-26 11:14, Steve Ebersole wrote:
>> > On Wed, Mar 26, 2014 at 10:12 AM, Steve Ebersole
>> > <steve at hibernate.org>wrote:
>> >
>> > > It does violate the spec though, that's the problem:
>> > >
>> >
>> > Well it *could* be read to violate the spec. That's inherently the
>> > problem
>> > with specs that use unclear wording; they can be read and argued
>> > multiple
>> > ways.
>> >
>> >
>> >
>> > >
>> > > "... It is not permitted to specify a field as Access(PROPERTY) or a
>> > > property as Access(FIELD)..."
>> > >
>> > > which imo is exactly what this is doing (specifying a property as
>> > > FIELD):
>> > >
>> > > @Id
>> > > @GeneratedValue
>> > > @Access(AccessType.FIELD)
>> > > public long getId() {
>> > > return id;
>> > > }
>> > >
>> > >
>> > >
>> > > On Wed, Mar 26, 2014 at 9:56 AM, Sanne Grinovero
>> > > <sanne at hibernate.org>wrote:
>> > >
>> > >> I do of course agree that people should use a single strategy and
>> > >> stick to it, so I agree with your reading about what the "general
>> > >> expectation" is.
>> > >>
>> > >> But the original test represents a quite naturally looking example
>> > >> and
>> > >> it's hard to justify why that should be considered illegal; I'd
>> > >> probably be more inclined in making user's life easier than try to
>> > >> lecture them about how a proper mapping should look like.
>> > >>
>> > >> Ignoring any annotation leads to waste of time and debugging
>> > >> frustration, so rather than silently discarding a mis-positioned
>> > >> annotation I'd prefer a fail-fast approach; that said I think just
>> > >> applying them all - as long as there are no obvious conflicting
>> > >> annotations - would be even more user friendly and doesn't seem to
>> > >> violate any specific wording of the spec.
>> > >>
>> > >> Sanne
>> > >>
>> > >>
>> > >> On 26 March 2014 13:57, Steve Ebersole <steve at hibernate.org> wrote:
>> > >> > Again from the spec (still discussing class-level Access(PROPERTY))
>> > >> > :
>> > >> "The
>> > >> > behavior is undefined if mapping annotations are placed on any
>> > >> > instance
>> > >> > variables defined by the class for which Access(FIELD) is not
>> > >> specified".
>> > >> >
>> > >> > Which to me implies that the expectation for switching access for a
>> > >> > particular field within such a class is to annotate the *field*
>> > >> > with
>> > >> > Access(FIELD).
>> > >> >
>> > >> > Also the footnote to this sections seems very relevant:
>> > >> >
>> > >> > "[8] ... It is not permitted to specify a field as Access(PROPERTY)
>> > >> > or a
>> > >> > property as Access(FIELD)..."
>> > >> >
>> > >> >
>> > >> >
>> > >> > On Wed, Mar 26, 2014 at 8:02 AM, Emmanuel Bernard <
>> > >> emmanuel at hibernate.org>
>> > >> > wrote:
>> > >> >>
>> > >> >> My reading at the time and what I did find more intuitive is what
>> > >> >> the
>> > >> >> test represents.
>> > >> >>
>> > >> >> Entity level @AccessType expresses where the annotations should
>> > >> >> be. Otherwise the position of @Id is used to find the access type
>> > >> >> to
>> > >> >> consider annotation wise.
>> > >> >>
>> > >> >> If for a few attributes I wish to use the alternative property
>> > >> >> access,
>> > >> I
>> > >> >> can add @AccessType next to the other annotations but expressing
>> > >> >> that
>> > >> >> the actual property value access is based on the alternative
>> > >> >> access.
>> > >> >> That way, all annotations are in the same place.
>> > >> >>
>> > >> >> On Wed 2014-03-26 11:12, Sanne Grinovero wrote:
>> > >> >> > As a user I would not expect the @Access annotation to be
>> > >> >> > treated as
>> > >> a
>> > >> >> > special case by the framework in terms of when an annotation is
>> > >> >> > ignored, as for example that I can put this on either properties
>> > >> >> > or
>> > >> >> > fields, and it would not be ignored, while other annotations
>> > >> >> > could be
>> > >> >> > ignored depending on the position.
>> > >> >> >
>> > >> >> > Also I highly doubt that there is a practical use case to
>> > >> >> > "comment" a
>> > >> >> > mapping annotation by moving it to the wrong position (say I
>> > >> >> > move a
>> > >> >> > @GeneratedValue from a field to a property when using FIELD
>> > >> >> > access):
>> > >> >> > that would be extremely confusing to maintain.
>> > >> >> >
>> > >> >> > The spec's wording states "When Access(PROPERTY) is applied to
>> > >> >> > an
>> > >> >> > [...] mapping annotations **may** be placed on .."
>> > >> >> > I'd stress that it doesn' t say "must" but "may", and also
>> > >> >> > doesn't
>> > >> >> > seem to strictly ban the opposite.
>> > >> >> >
>> > >> >> > As a user if I put a mapping annotation anywhere I expect it to
>> > >> >> > be
>> > >> >> > respected, so I would expect the framework to work on the union
>> > >> >> > of
>> > >> the
>> > >> >> > possible positions, and probably even to throw an exception on
>> > >> >> > conflicting options. The @Access property would then only be
>> > >> >> > used to
>> > >> >> > state which access strategy should be used (and a nice effect is
>> > >> >> > tha
>> > >> >> > the name becomes particularly self-explanatory too).
>> > >> >> >
>> > >> >> > Also there are many types of possible contradictions in the
>> > >> >> > mapping
>> > >> >> > options:
>> > >> >> >
>> > >> >> > public class Course {
>> > >> >> > @Id @GeneratedValue(strategy=TABLE)
>> > >> >> > private long id;
>> > >> >> > ...
>> > >> >> >
>> > >> >> > @Id @GeneratedValue(strategy=SEQUENCE)
>> > >> >> > public long getId() {
>> > >> >> > return id;
>> > >> >> > }
>> > >> >> >
>> > >> >> > Or you could have a stronger conflict which isn't solvable via
>> > >> >> > AccesType "rules" either:
>> > >> >> >
>> > >> >> > public class Course {
>> > >> >> > @Id @GeneratedValue(strategy=TABLE)
>> > >> >> > @Access(AccessType.FIELD)
>> > >> >> > private long id;
>> > >> >> > ...
>> > >> >> >
>> > >> >> > @Id @GeneratedValue(strategy=SEQUENCE)
>> > >> >> > @Access(AccessType.PROPERTY)
>> > >> >> > public long getId() {
>> > >> >> > return id;
>> > >> >> > }
>> > >> >> >
>> > >> >> > This last example is the reason why I think you should always
>> > >> >> > consistently look at both to collect mapping options, and
>> > >> >> > possibly
>> > >> >> > throw runtime exceptions.
>> > >> >> >
>> > >> >> > Sanne
>> > >> >> >
>> > >> >> >
>> > >> >> >
>> > >> >> >
>> > >> >> > On 26 March 2014 04:13, Steve Ebersole <steve at hibernate.org>
>> > >> >> > wrote:
>> > >> >> > > >From the test
>> > >> >> > >
>> > >> >> > >
>> > >>
>> > >> org.hibernate.test.annotations.access.jpa.AccessMappingTest#testExplicitPropertyAccessAnnotationsWithHibernateStyleOverride
>> > >> >> > > we have the following:
>> > >> >> > >
>> > >> >> > >
>> > >> >> > > @Entity
>> > >> >> > > @Access(AccessType.PROPERTY)
>> > >> >> > > public class Course3 {
>> > >> >> > > private long id;
>> > >> >> > > ...
>> > >> >> > >
>> > >> >> > > @Id
>> > >> >> > > @GeneratedValue
>> > >> >> > > @Access(AccessType.FIELD)
>> > >> >> > > public long getId() {
>> > >> >> > > return id;
>> > >> >> > > }
>> > >> >> > > ...
>> > >> >> > > }
>> > >> >> > >
>> > >> >> > > The test asserts that this is a valid mapping. Granted that
>> > >> >> > > the
>> > >> spec
>> > >> >> > > is
>> > >> >> > > very unclear here, so I might be missing something. The
>> > >> >> > > pertinent
>> > >> >> > > spec
>> > >> >> > > section here states:
>> > >> >> > >
>> > >> >> > >
>> > >> >> > >
>> > >> >> > >
>> > >> >> > >
>> > >> >> > >
>> > >> >> > >
>> > >> >> > >
>> > >> >> > >
>> > >> >> > >
>> > >> >> > > *<quote>When Access(PROPERTY) is applied to an entity class,
>> > >> >> > > mapped
>> > >> >> > > superclass, or embeddableclass, mapping annotations may be
>> > >> >> > > placed
>> > >> on
>> > >> >> > > the
>> > >> >> > > properties of that class, and the persistenceprovider runtime
>> > >> accesses
>> > >> >> > > persistent state via the properties defined by that class. All
>> > >> >> > > proper-ties
>> > >> >> > > that are not annotated with the Transient annotation are
>> > >> persistent.
>> > >> >> > > WhenAccess(PROPERTY) is applied to such a class, it is
>> > >> >> > > possible to
>> > >> >> > > selectively designate indi-vidual attributes within the class
>> > >> >> > > for
>> > >> >> > > instance
>> > >> >> > > variable access. To specify a persistent instancevariable for
>> > >> access
>> > >> >> > > by the
>> > >> >> > > persistence provider runtime, that instance variable must be
>> > >> >> > > desig-nated
>> > >> >> > > Access(FIELD).</quote>*
>> > >> >> > >
>> > >> >> > >
>> > >> >> > > I can see a few different ways to read that:
>> > >> >> > >
>> > >> >> > > 1) @Access can be placed on the attribute to define both where
>> > >> >> > > to
>> > >> look
>> > >> >> > > for
>> > >> >> > > mapping annotations and the runtime access strategy for a
>> > >> >> > > given
>> > >> >> > > attribute.
>> > >> >> > > Here, we'd do:
>> > >> >> > >
>> > >> >> > > @Entity
>> > >> >> > > @Access(AccessType.PROPERTY)
>> > >> >> > > public class Course3 {
>> > >> >> > > @Id
>> > >> >> > > @GeneratedValue
>> > >> >> > > @Access(AccessType.FIELD)
>> > >> >> > > private long id;
>> > >> >> > > ...
>> > >> >> > >
>> > >> >> > > public long getId() {
>> > >> >> > > return id;
>> > >> >> > > }
>> > >> >> > > ...
>> > >> >> > > }
>> > >> >> > >
>> > >> >> > > 2) @Access can be placed on the attribute to define the
>> > >> >> > > runtime
>> > >> access
>> > >> >> > > strategy for a given attribute, but the class/hierarchy
>> > >> >> > > AccessType
>> > >> >> > > controls
>> > >> >> > > where to look for mapping annotations. This would lead to:
>> > >> >> > >
>> > >> >> > > @Entity
>> > >> >> > > @Access(AccessType.PROPERTY)
>> > >> >> > > public class Course3 {
>> > >> >> > > @Access(AccessType.FIELD)
>> > >> >> > > private long id;
>> > >> >> > > ...
>> > >> >> > >
>> > >> >> > > @Id
>> > >> >> > > @GeneratedValue
>> > >> >> > > public long getId() {
>> > >> >> > > return id;
>> > >> >> > > }
>> > >> >> > > ...
>> > >> >> > > }
>> > >> >> > >
>> > >> >> > > The test seems to illustrate that our legacy code made yet a
>> > >> >> > > 3rd
>> > >> >> > > reading of
>> > >> >> > > this passage such that @Access is still considered a "mapping
>> > >> >> > > annotation"
>> > >> >> > > even though that seems to directly contradict "To specify a
>> > >> persistent
>> > >> >> > > instance
>> > >> >> > > variable for access by the persistence provider runtime, that
>> > >> instance
>> > >> >> > > variable must be desig-
>> > >> >> > > nated Access(FIELD)."
>> > >> >> > >
>> > >> >> > >
>> > >> >> > > Is there some other passage I am missing that bears on what to
>> > >> >> > > do
>> > >> >> > > here?
>> > >> >> > > How do y'all feel about that passage and its implications on
>> > >> >> > > this
>> > >> >> > > test
>> > >> >> > > mapping?
>> > >> >> > > _______________________________________________
>> > >> >> > > 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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