= JDO Annotations

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The table below lists the xref:pjdo:ROOT:about.adoc[JDO/DataNucleus] annotations currently recognized by Apache Isis.


.JDO Annotations
[cols="2,4a,1,1", options="header"]
|===
|Annotation
|Purpose
|Layer
|Applies to


|xref:refguide:applib-ant:Column.adoc[@javax.jdo.annotations. +
Column]
|Used to determine whether a property is mandatory or optional.  For `String` and `BigDecimal` properties, used to determine length/precision/scale.

|Domain / persistence
|Property


|xref:refguide:applib-ant:Discriminator.adoc[@javax.jdo.annotations. +
Discriminator]
|Override for the object type, as used in `Bookmark`s, URLs for xref:vro:ROOT:about.adoc[RestfulObjects viewer] and elsewhere. +

Note that the discriminator overrides the object type that may otherwise be inferred from the xref:refguide:applib-ant:PersistenceCapable.adoc[@PersistenceCapable] annotation.
|Domain / persistence
|Class


|xref:refguide:applib-ant:NotPersistent.adoc[@javax.jdo.annotations. +
NotPersistent]
|Used to determine whether to enforce or skip some metamodel validation for `@Column` versus equivalent Isis annotations.

|Domain / persistence
|Property



|xref:refguide:applib-ant:PersistenceCapable.adoc[@javax.jdo.annotations. +
PersistenceCapable]
|Used to build Apache Isis' own internal identifier for objects. +

If the `schema` attribute is specified (and if xref:refguide:applib-ant:Discriminator.adoc[@Discriminator] __hasn't__ been specified), is also used to derive the object type, as used in `Bookmark`s, URLs for xref:vro:ROOT:about.adoc[RestfulObjects viewer] and elsewhere.

|Domain / persistence
|Class


|xref:refguide:applib-ant:PrimaryKey.adoc[@javax.jdo.annotations. +
PrimaryKey]
|Used to ensure Apache Isis does not overwrite application-defined primary keys, and to ensure is read-only in the UI.

|Domain / persistence
|Property



|===



Isis also parses the following JDO annotations, but the metadata is currently unused.

.JDO Annotations (unused within Apache Isis)
[cols="2,4a,1,1", options="header"]
|===
|Annotation
|Purpose
|Layer
|Applies to


|@javax.jdo.annotations. +
DataStoreIdentity
|Unused
|Persistence
|Class


|@javax.jdo.annotations. +
Queries
|Unused
|Persistence
|Class


|@javax.jdo.annotations. +
Query
|Unused
|Persistence
|Class


|@javax.jdo.annotations. +
Version
|Unused
|Persistence
|Class


|===



