java - 为什么Hibernate在一对一关系的情况下要放inner join？

Question

我有两个实体:UnsubscribedPartner 用于从邮寄合作伙伴取消订阅

@Entity
@Table(schema = "mailing", name = "unsubscribed_partner")
public class UnsubscribedPartner {

    @Id
    @Column(name = "partner_id")
    private int partnerId;

    @Column(name = "unsubscription_date")
    private Date date;

    @OneToOne(targetEntity = Partner.class, fetch = FetchType.EAGER)
    @JoinColumn(name = "partner_id")
    private Partner partner;

    //GET, SET
}

Partner 合作伙伴的类

@Entity
@Table(schema = "partner", name = "partner")
public class Partner {

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

    @Column(name = "email")
    private String email;

    @OneToOne(fetch = FetchType.EAGER, mappedBy = "partner")
    private UnsubscribedPartner unsubscribedPartner;

    //GET, SET
}

我构造了以下条件查询:

String email;
//...
Criteria criteria = getSession().createCriteria(Partner.class);
if(!(email == null)){
    criteria.add(Restrictions.eq("email", email));
}
Criteria unsubscribedCrieria = criteria.createCriteria("unsubscribedPartner", "unsbcr");
unsubscribedCrieria.add(Restrictions.isNull("unsbcr.reason"));

但是SQL查询的结果是

    select
        count(*) as y0_ 
    from
        partner.partner this_ 
    inner join
        mailing.unsubscribed_partner unsbcr1_ 
            on this_.id=unsbcr1_.partner_id 
    where
        unsbcr1_.unsubscription_reason_id is null

内部联接在这里不合适，因为unsubscribed_pa​​rtner表可能不是partner表中的任何合作伙伴，因此我需要LEFT OUTER JOIN来代替。我该如何解决这个问题？

Answer 1

documentation声明 createCriteria(String, String) 在功能上等同于 createCriteria(String, String, int) 使用 CriteriaSpecification.INNER_JOIN 作为 joinType。

因此，请尝试使用 createCriteria("unsubscribedPartner", "unsbcr", CriteriaSpecification.LEFT_JOIN) 来代替。