Answer by Nicolae Albu for One to many map in Hibernate - error

Use nullable = false to tell Hibernate that the join column cannot be null:

@Entity@Table(name = "ITEM")public class Item  implements Serializable {    // ...    @OneToMany(cascade = CascadeType.ALL)    @JoinColumn(name = "ID_ITEM", referencedColumnName = "ID", nullable = false)    private List<ItemDetail> itemDetails;    // ...}

and remove the itemId property from ItemDetail as it is already mapped by the @JoinColumn annotation. If you need the itemId, then use a bi-directional relationship (hold a reference to the entire Item object, not just the ID).