[hibernate-dev] Another @Access quandry
Steve Ebersole
steve at hibernate.org
Wed Mar 26 14:37:23 EDT 2014
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.
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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