@MappedSuperclass is not an @Entity in JPA?
Solution 1
I can suggest two solutions:
Change Inheritance
The exception you get clearly describes your problem: User
is not an entity. Any class declared as superclass with the interface @MappedSuperclass
cannot be an entity (in standard JPA - depends on your JPA-provider)... let me point you to an answer I just gave to quite a similar problem
--> Superclass-Types
So defining your superclass as an abstract entity will give you the desired behaviour, you described.
Extra:
If you choose your inheritance mapping strategy as @Inheritance(strategy = InheritanceType.SINGLE_TABLE)
you don't even need multiple database-tables. Here is a good example: JPA Single-Table Inheritance
Change Model (suggested)
Don't split your user entity in several entities just by their roles. Make an Enum
with all your desired roles and add it as a field to your User
-entity. This is widely more common, unless u need your admin, guests etc to be an own object...
Solution 2
@MappedSupperclass
is different than the @Inheritance
annotation.
@MappedSuperclass
tells the JPA provider to include the base class persistent properties as if they were declared by the child class extending the superclass annotated with @MappedSuperclass
.
However, the inheritance is only visible in the OOP world, since, from a database perspective, there's no indication of the base class. Only the child class entity will have an associated mapped table.
The @Inheritance
annotation is meant to materialize the OOP inheritance model in the database table structure. More, you can query a base class annotated with @Inheritance
but you can't do that for a base class annotated with @MappedSuperclass
.
Solution 3
Sometimes to inherit child class we create a parent class but we don't use it as a table.Inheriting that parent class we create various table.That's why we don't use @Entity in a parent class. Rather than we use @MappedSuperClass in a parent or super class.
Rakim
Updated on January 10, 2021Comments
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Rakim over 3 years
So I am using DerbyDB and I am setting up some entities. I have a
@MappedSuperclass
which is used as a superclass for some entities (@Entity
). More specifically, I have a superclassUser
and 3 subclasses namelyadmin
,regular
andguest
. Now I have a different entity, let's sayfile
that should reference (as one of its fields) its owner. So I created a field calledUser owner
. The error I get is:Exception Description: [File] uses a non-entity [User] as target entity in the relationship attribute [field owner].
Is there a workaround?
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Rakim about 8 yearsI thought of that but can't really change model as each user has it's own attributes. Only a few basic stuff applies to all user-types
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XiCoN JFS about 8 yearsOk, i see. If there are a lot of different extra attributes I advice to use InheritanceType.JOINED. SINGLE_TABLE otherwise will result in a lot of redundant data (empty columns)... happy coding =)