[hibernate-dev] Mapping JPA's @MapKeyEnumerated and @Enumerated on native-enum supporting datastores

[Gunnar Morling]

> I guess we could, but it's sad that we'd still have to default to the
> "wrong" mapping,
> at least for all those people who won't read all of our docs.

The default for our custom @Enumerated could be NATIVE, but I agree people
need to know about that instead of the JPA one.

> Would that live in OGM or ORM ?

Good question, depends on whether there is any RDBMS with native enum
support?


2016-08-26 13:02 GMT+02:00 Sanne Grinovero <sanne at hibernate.org>:

> On 26 August 2016 at 10:34, Gunnar Morling <gunnar at hibernate.org> wrote:
> > How about having a custom @Enumerated annotation which offers NATIVE as
> an
> > additional choice?
>
> I guess we could, but it's sad that we'd still have to default to the
> "wrong" mapping,
> at least for all those people who won't read all of our docs.
>
> Would that live in OGM or ORM ?
>
> >
> > 2016-08-26 10:16 GMT+02:00 Emmanuel Bernard <emmanuel at hibernate.org>:
> >>
> >> Can you give HotRod's example of native enum - I imagine Protobuf ?
>
> From the OGM testsuite:
>
> @Entity
> public class Bookmark {
>
> public enum Classifier {
> HOME, WORK
> }
>
> @Id
> private String id;
> @Enumerated(EnumType.STRING)
> private Classifier classifier;
> [...]
> }
>
> Is mapped as:
>
>   message Bookmark {
>     required string id = 1;
>     optional string classifier = 2;
>   [...]
>
> (correctly as it's explicitly requesting a STRING EnumType)
>
> A more "native" Protobuf mapping would look like:
>
>   enum Classifier {
>     HOME = 0;
>     WORK = 1;
>   }
>
>   message Bookmark {
>     required string id = 1;
>     optional Classifier classifier = 2;
>   [...]
>
> I had already implemented this, just realising later that there's no
> way to enable this better looking mapping.
>
> >>
> >> The issue I see is that ordinal could be an acceptable explicit decision
> >> that would not be available to the user if you use default as native.
> >>
> >> I'm tempted to go native all the time at the detriment of people that
> >> need high customization.
>
> I'd be tempted too as the second mapping looks much more natural,
> however this would break things for people who need it to be an
> integer, e.g. if they have other clients who expect an int.
> On the other hand, the "I need compatibility with another client"
> argument is quite weak, as at this stage the Hot Rod Dialect generates
> its own schema and pretty much mandates using the one it generates.
>
> Proposal: I have it mapped as "native enums" by default, and give a
> global configuration property to honour the annotations instead? This
> would be a global setting though, so if one wants one attribute
> "native encoded" and another "int encoded" that wouldn't be possible.
>
> Thanks,
> Sanne
>
> >>
> >> Emmanuel
> >>
> >> On Mon 2016-08-15 18:14, Sanne Grinovero wrote:
> >> > In the context of Hibernate OGM, it turns out that some datastores
> >> > have a rather nice "native" support for enums.
> >> >
> >> > We aim to map each property of the user's domain model to its most
> >> > appropriate "physical type", unless the choice is overriden by the an
> >> > explicit user request.
> >> >
> >> > In the case of an Enum, JPA annotations such as @Enumerated have an
> >> > attribute EnumType to choose the physical representation:
> >> >
> >> > public enum EnumType {
> >> >     /** Persist enumerated type property or field as an integer. */
> >> >     ORDINAL,
> >> >
> >> >     /** Persist enumerated type property or field as a string. */
> >> >     STRING
> >> > }
> >> >
> >> > However, there's no support for a "NATIVE". Also, the annotation
> >> > specifies that "ORDINAL" is the default value so I can't just assume
> >> > that the user didn't specify anything and we're good to use our own
> >> > NATIVE implementation.
> >> >
> >> > Assuming that we can't change the JPA spec, any suggestion on when I
> >> > could have the Hot Rod dialect for OGM to actually produce a "nice"
> >> > mapping into native enums?
> >> >
> >> > I'm tempted to just use natives all the time; In the case in which the
> >> > user opted for "STRING" I could drop a warning - or decide to honour
> >> > that - but in case of ORDINAL I just can't tell if it's a default
> >> > choice or not so I think a warning would be too much.
> >> >
> >> > Another alternative would be that I "go native" when the @Enumerated
> >> > annotation isn't specified at all: looks like this mapping is valid
> >> > according to ORM as it seems to treat it as if there was an implicit
> >> > @Enumerated annotation; I'm not happy about having to rely on people
> >> > to not use an explicit annotation though.
> >> >
> >> > Thanks,
> >> > Sanne
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