How to mapping the relationship Store <- Stock -> Product with OpenJPA?

Question

I have the next relationship:

Currently, I have the next code:

@Embedded
public class StockPK implements Serializable {

    private int storeId;

    private int productId

}

@Entity
public class Stock implements Serializable {

    @EmbeddedId
    private StockPK id;

    private int cantidad;

    @ManyToOne
    private Store store;

    @ManyToOne
    private Product product;

}

But the DDL generated (I'm using OpenJPA in TomEE) adds two aditional fields.

CREATE TABLE STOCK (
    productId  INTEGER NOT NULL,
    storeId    INTEGER NOT NULL,
    quantity   INTEGER NOT NULL,
    PRODUCT_ID INTEGER         ,
    STORE_ID   INTEGER         ,
    PRIMARY KEY (productId, storeId)
)

How should specify this relationship?

Answer 1

Thanks JBNizet :) — The solution was as follows:

@Embeddable
public class StockPK implements Serializable {

    @Column(name = "store_id")
    private int storeId;

    @Column(name = "product_id")
    private String productId;

    // Getters, setters, hashCode, equals

}

@Entity
@Table(name = "stock")
public class Stock implements Serializable {

    @EmbeddedId
    private StockPK id;

    @MapsId("storeId")
    @ManyToOne
    private Store store;

    @MapsId("productId")
    @ManyToOne
    private Product product;

    @Column(nullable = false)
    private int quantity;

    // Getters, setters

}

@Entity
@Table(name = "store")
public class Store implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    // Other fields, getters, setters ...

}

@Entity
@Table(name = "product")
public class Product implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    // Other fields, getters, setters ...

}