JPA : Entity extend with entity - jpa

Question

How can I extend an entity with another entity but both of them referring to the same table ? Is it possible ? The structure is something like this :
#Entity
#Table(name = "users")
#NamedQuery(name="User.findAll", query="SELECT u FROM User u")
public class User implements Serializable{
private int id;
private String name;
}
#Entity
#Table(name = "users")
#NamedQuery(name="SubUser.findAll", query="SELECT su FROM SubUser su")
public class SubUser extends User {
#Override
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
public int getId() {
return super.getId();
}
//- Other fields and getter setter
}
I tried this way Extend JPA entity to add attributes and logic
but I got this exception
org.hibernate.mapping.SingleTableSubclass cannot be cast to org.hibernate.mapping.RootClass
Update 1
I already put the #Id for the SubUser because the #Entity shows this exception
The entity has no primary key attribute defined

Answer 1

Add the #Inheritance annotation to the super class
Implement Serializable
Add a getter for id (you don't need a setter necessarily)
id should be Integer, not int, so that you can represent unassigned ids with null.
Code:
#Entity
#Table(name = "users")
#Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class User implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private Integer id;
private String name;
public Integer getId() {
return id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
#Entity
public class SubUser extends User {
}

Answer 2

Any basic JPA docs would describe inheritance, discriminators and use of #Id.
#Entity
#Inheritance(strategy=InheritanceType.SINGLE_TABLE)
#DiscriminatorColumn(name="DISCRIM", discriminatorType=DiscriminatorType.STRING)
#DiscriminatorValue("User")
#Table(name="users")
#NamedQuery(name="User.findAll", query="SELECT u FROM User u")
public class User implements Serializable{
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private int id;
private String name;
}
#Entity
#DiscriminatorValue("SubUser")
#NamedQuery(name="SubUser.findAll", query="SELECT su FROM SubUser su")
public class SubUser extends User {
}