Extending EJB3 Objects

Small and fast tip.

In order to be able to extend an EJB Entity object (be it a main object or a primary key embbedable) you need to write the MappedSuperclass anotation in the super class.

The following is taken from hibernate documentation :

@MappedSuperclass
public class BaseEntity {
    @Basic
    @Temporal(TemporalType.TIMESTAMP)
    public Date getLastUpdate() { ... }
    public String getLastUpdater() { ... }
    ...
}

@Entity class Order extends BaseEntity {
    @Id public Integer getId() { ... }
    ...
}

Some other notes taken from the documentation :

• Properties from superclasses not mapped as @MappedSuperclass are ignored;
• The access type (field or methods), is inherited from the root entity, unless you use the Hibernate annotation @AccessType;
• Any class in the hierarchy non annotated with @MappedSuperclass nor @Entity will be ignored.

Read the documentation to understand it fully : http://docs.jboss.org/hibernate/stable/annotations/reference/en/html/entity.html chapter 2.2.4.4

Please note that even though i’ve used the Hibernate documentation as a reference this anotation also exists in javax.persistence so it can be used with JPA