如何注释抽象类实例的组成？

Question

I have a design of Person as shown in the following picture. The design is to allow a person to change his role from Staff to Student , Student to Faculty and so on.

I want to persist this system to DB using hibernate annotation. Does anyone know how to do that?

Thanks a lot!

Answer 1

So you have 1:N relation between Entity Persona and abstract entity Person Role. Think this may work for you.

@Entity
public class Person {
  // Here you have all roles in some collection.
  @OneToMany(mappedBy="person", fetch=FetchType.LAZY)
  private List<PersonRole> roles;
  ...
}

@Entity
public abstract class PersonRole {
    @ManyToOne
    @JoinColumn(name="PERSON_ID")
    private Person person;
    ...
}

@Entity
public class Staff extends PersonRole {
   ...
}

Also don't forget to set proper

@Inheritance(strategy=InheritanceType.<strategy>)

to define how class model is mapped to relational model.

Edit: Unfortunately @MappedSuperclass can't be used in relations mapping so this is not an option here as long as you would like to have PersonRole collection in Person entity.