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note about embeddable types and polymorphism

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Gavin 2023-05-15 13:28:52 +02:00 committed by Christian Beikov
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documentation/src/main/asciidoc/introduction/Entities.adoc
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@ -865,6 +865,9 @@ JPA provides an `@Embedded` annotation to identify an attribute of an entity tha
This annotation is completely optional, and so we don't usually use it. This annotation is completely optional, and so we don't usually use it.
==== ====
On the other hand a reference to an embeddable type is _never_ polymorphic.
One `@Embeddable` class `F` may inherit a second `@Embeddable` class `E`, but an attribute of type `E` will always refer to an instance of that concrete class `E`, never to an instance of `F`.
Usually, embeddable types are stored in a "flattened" format. Usually, embeddable types are stored in a "flattened" format.
Their attributes map columns of the table of their parent entity. Their attributes map columns of the table of their parent entity.
Later, in <<mapping-embeddables>>, we'll see a couple of different options. Later, in <<mapping-embeddables>>, we'll see a couple of different options.