CODEWITHSUNDEEP
javainheritancejpapersistence
Mike Minicki
Mike Minicki

Reputation: 8466

Persisting non-entity class that extends an entity (jpa) - example?

The JPA tutorial states that one can have a non-entity that extends entity class:

Entities may extend both entity and non-entity classes, and non-entity classes may extend entity classes. - http://java.sun.com/javaee/5/docs/tutorial/doc/bnbqa.html

Is it possible to persist such structure?

I want to do this:

@Entity
abstract class Test { ... }

class FirstConcreteTest extends Test { ... } // Non-ntity
class SecondConcreteTest extends Test { ... } // Non-entity

Test test = new FirstConcreteTest();

em.persist(test);

What I would like it to do is to persist all fields mapped on abstract Test to a common database table for all concrete classes (first and second), leaving all fields of first and second test class unpersisted (these can contain stuff like EJBs, jdbc pools, etc).

And a bonus question. Is it possible to persist abstract property too?

@Entity
abstract class Test {

    @Column
    @Access(AccessType.PROPERTY)
    abstract public String getName();

}

class SecondConcreteTest extends Test {
    public String getName() {
        return "Second Concrete Test";
    }
}

Upvotes: 2

Views: 11316

Answers (2)

Pascal Thivent
Pascal Thivent

Reputation: 570385

Upvotes: 2

DataNucleus
DataNucleus

Reputation: 15577

Read that link again. "An entity class must follow these requirements: * The class must be annotated with the javax.persistence.Entity annotation."

If a class is a non-Entity, then it is a non-Entity so is not persisted as an Entity. Anything persistable has to be marked as such, so mark your subclass as an Entity, and mark fields that you don't want to persist as "transient"

Upvotes: 2

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