為什么在一對一關系的情況下，Hibernate會進行內部聯接？

Question

我有兩個實體： UnsubscribedPartner用於退訂郵件合作伙伴

@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伙伴的班級

@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
}

我構造了以下條件查詢：

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"));

但是結果SQL查詢是

    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

內LEFT OUTER JOIN在這里不合適，因為unsubscribed_partner表可能不是partner表中的任何伙伴，因此我需要LEFT OUTER JOIN 。 我該如何解決？

Answer 1

該文檔指出， 使用 CriteriaSpecification.INNER_JOIN for the joinType ， createCriteria(String, String)在功能上等效於 createCriteria(String, String, int) 。

因此，請嘗試使用createCriteria("unsubscribedPartner", "unsbcr", CriteriaSpecification.LEFT_JOIN) 。