[hibernate-dev] @Entity and inheritance with annotations

[Hardy Ferentschik]

On Mar 14, 2012, at 9:17 PM, Steve Ebersole wrote:

> Can someone help me understand whether this is valid annotation mapping:
> 
> @Entity
> class A {
> }
> 
> @Entity
> class B extends A {
> }

That's valid. The @Inheritance annotation is optional. If not specified InheritanceType.SINGLE_TABLE is used.

> My understanding was that an @Entity extending an @Entity had to specify 
> an inheritance strategy?  And that this example is really the point of 
> @MappedSuperclass:
> 
> @MappedSuperclass
> class A {
> }
> 
> @Entity
> class B extends A {
> }

Citing from the spec here:

An entity may inherit from a superclass that provides persistent entity state and mapping information,
but which is not itself an entity. Typically, the purpose of such a mapped superclass is to define state
and mapping information that is common to multiple entity classes.

--Hardy