Hi all, i've read some tutorials for Inheritance Mapping, which couldnt quitely solve my questions.

Say i have an abstract class : User
And 3 more other subclasses : UserA, UserB, UserC, those all extend User.

Every Subclass has its own table, Superclass User, meanwhile, doesn't.

In my other class Website i have a ArrayList, or should i say Collections, of Users.

The list should fetch all users of the Website.

Which strategy should i use ? I thought of MappedSuperclass, but since in my Website class the List is of User type, so am not sure what to do here.

Thanks for any help!

If you use @MappedSuperclass, then the inheritance model is materialized only in Java, but not the DB. Hence, you cannot run polymorphic queries or map polymorphic associations.

The only reasonable way to make it work is to use JOINED inheritance here and accept the fact that the common columns will be mapped to the base class associated table.

You should never use TABLE_PER_CLASS because it's not very efficient in terms of SQL statements. While JOINED is probably the first choice for your mapping requirements, if the subclasses don't differ too much, then you should consider using SINGLE_TABLE inheritance which is the most efficient inheritance strategy.

Hi, i have read some examples about Joined Inheritance, sadly it requires that my SuperClass must have its own table, which i dont have. Am i forced to use @MappedSupperclass in this case?

If you cannot alter the database, then you will need to use @MappedSuperclass and you will not be able to do polymorphic queries and associations.