I am making a POS like system. I wonder how to map subclass using JPA (this is for my DAO). Product class has product details and OrderProduct class has information about the Product and details about the order.

@Entity
@Table(name="products")
public class Product implements Serializable{
    @Id
    @Column(name="id")
    @GeneratedValue(strategy = GenerationType.AUTO
    public int getId(){ return id;}

    /**
     Other get/set methods
    */
}

@Entity
@Table(name="order_products")
public class OrderProduct extends Product{
        @Id
        @Column(name="id")
        @GeneratedValue(strategy = GenerationType.AUTO)
        public int getId(){ return id;}

        /**
         Other get/set methods
        */
}

I got complain about duplicate @Id. But OrderProduct class really need another id than the product one. How should I map this?

DB is something like this

Table products
id int
name varchar(32)

Table order_product
id int
quantity int
productid int fk referencing product table

Would @IdClass or @AttributeOverride help?