HI there,
supposing to have an abstract SuperClass, with a single table inheritance, like this:

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorFormula("...")
@Table(name = "groups")
public abstract class AbstractGroup<H extends AbstractGroup<H>> implements Serializable {
  @ManyToOne
  @JoinColumn(name = "parent_groupid", referencedColumnName = "groupid")
  private H parent;
}

You can receive this error message:

Property entity.AbstractGroup.parent has an unbound type and no explicit target entity. Resolve this Generic usage issue or set an explicit target attribute (eg @OneToMany(target=) or use an explicit @Type.

I think that you could accept target type as an instance of AbstractGroup, because you're using inheritance on a single table, so you could know which is the right class.

What do you think about this?