@Entity
public class BasketItem
{
   @ManyToOne(cascade = CascadeType.MERGE, fetch = FetchType.EAGER)
    @JoinColumn(name = "BASKET_ID")
    public Basket basket;
}

@Entity
public class Basket
{
    @OneToMany(mappedBy = "basket", cascade = CascadeType.ALL,fetch = FetchType.LAZY)
    private List<BasketItem> basketItemsList;

    public Basket()
    {
        basketItemsList = new ArrayList<BasketItem>();  //чтобы избежать NullPointerException
    }

   public BasketItem addBasketItem(BasketItem basketItem)
    {
        basketItemsList.add(basketItem);
        basketItem.setBasket(this);
        return basketItem;
    }
}