Hibernate / JPA：此条件查询不包含隐式ON子句

Question

JPWH book表示使用Hibernate的条件查询中的连接操作会产生带有外键约束的on子句。我在数据库中添加了这些外键约束：

alter table BID add foreign key (BIDDER_ID) references USER (ID)
alter table BID add foreign key (ITEM_ID) REFERENCES ITEM (ID)
alter table ITEM add foreign key (SELLER_ID) REFERENCES ITEM (ID)

所以我期待这个标准查询：

private static void implicitJoin(EntityManager em) {
    CriteriaBuilder cb = em.getCriteriaBuilder();
    CriteriaQuery criteria = cb.createQuery();

    Root<Bid> b = criteria.from(Bid.class);
    criteria.select(b).where(
            cb.equal(
                    b.get("item").get("seller").get("username"), "johndoe")
    );

    TypedQuery<Item> query = em.createQuery(criteria);
    List<Item> results = query.getResultList();
}

翻译成：

select b.* from BID b inner join ITEM i on b.ITEM_ID = i.ID inner join
USER u on i.SELLER_ID = u.ID where u.USERNAME = 'johndoe';

但是我得到了这个SQL语句：

    /* select
        generatedAlias0 
    from
        Bid as generatedAlias0 
    where
        generatedAlias0.item.seller.username=:param0 */ select
            bid0_.BID_ID as BID_ID1_0_,
            bid0_.BIDDER_ID as BIDDER_I2_0_,
            bid0_.ITEM_ID as ITEM_ID3_0_ 
        from
            BID bid0_ cross 
        join
            ITEM item1_ cross 
        join
            USER user2_ 
        where
            bid0_.ITEM_ID=item1_.id 
            and item1_.SELLER_ID=user2_.id 
            and user2_.username=?

如何将bid0_.ITEM_ID=item1_.id and item1_.SELLER_ID=user2_.id放入on子句？可能吗？这是实体：

@Entity
@Table(name = "BID")
public class Bid implements Serializable {

    @Id @GeneratedValue
    @Column(name = "BID_ID")
    private Long id = null;

    @ManyToOne
    @JoinColumn(name = "ITEM_ID", nullable = false, updatable = false, insertable = false)
    private Item item;

    @ManyToOne
    @JoinColumn(name = "BIDDER_ID", nullable = false, updatable = false)
    private User bidder;
}

@Entity
@Table(name = "ITEM")
public class Item implements Serializable {

    @Id
    private Long id = null;

    private String name;
    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "SELLER_ID", nullable = false)
    private User seller;

    @OneToMany(mappedBy = "item", fetch = FetchType.LAZY)
    private List<Bid> bids;
}

@Entity
@Table(name = "USER")
public class User implements Serializable {

    @Id
    private Long id = null;
    private String firstname;
    private String lastname;
    private String username; // Unique and immutable
}