how to define an Entity for interface

[koeiease]

hello,
i have some classes:

Interface Item{...}
Class ItemImplA implements Item{...}
Class ItemImplB implements Item{...}
@Entity
Class Order{
 Item item;
 ...
}

i think @TargetEntity can only use for one class.but now i have 2 classes implements Item, how can i write annotation for item in Order?