hibernategrailsinheritancepolymorphismgrails-orm

abstract class in GORM polymorphism

I'm working on a Grails project, Grails version: 2.2.0.
I have these classes:

public abstract class A {}
public class B extends A {}
public class C extends A {}

For now, everything is OK
class A is in: src/groovy so in DB I have two tables B & C.
now I add a new class:

public class D{
A aa
}

now that no longer works because hibernate doesn't cognize the Type A. One solution is to omit the abstract term but that allows instantiation of A object which is not so right! Does any one have an idea about how fix this problem?
thank you

Solution

  • The problem is this: GORM/Hibernate must be able to instantiate the domain class properties (except for the transient ones, of course). Because of this, a property cannot be of an abstract type. Interfaces don't work for the same reason.

    To keep inheritance, unfortunately you'll have to do that not so right thing: drop the abstract and make A a domain class.