Hi konstantin thanks alot for your reply, do you mean that i shoul have : @Entity @Table(name = "Daughter") @IdClass(DaughterKey.class) @PrimaryKeyJoinColumn(name = "Mother_id") public class Daughter extends Mother{ private String daughter_id; @Id private DaughterKey myKey=new DaughterKey(); public Daughter(){ super(); myKey.setMotherId(super.getId()); myKey.setDaughterId(getDaugherId())), } //.. getter/setter for all fields } instead of : @Entity @Table(name = "Daughter") @IdClass(DaughterKey.class) @PrimaryKeyJoinColumn(name = "Mother_id") public class Daughter extends Mother{ @Id private String daughter_id; public Daughter(){ super();} //.. getter/setter for all fields } Is it your idea ? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3984978#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...