hibernate - JPA如何选择没有多个属性的对象

Question

我使用休眠 3.5.4-final。我有两个 JPA 课程。

    @Entity
    @Table(name = "SPI_V_OP_OBJ_SUBJECT_VR")
    public class OpSubject_vr extends PersistenceEntity implements Serializable {

        private static final long serialVersionUID = 1858749317461707015L;
        /** id */
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        @Column(name = "ID",
                nullable = false)
        private Long id;

        /** name */
        @Column(name = "F_NAME")
        private String f_name;


        /** type */
        @Column(name = "SUBJECT_TYPE")
        private String subject_type;


        /** okved */
        @ManyToMany
        @JoinTable(name = "SPI_V_OP_OBJ_SUBJECT_VR_OKVED",
                   joinColumns = {@JoinColumn(name = "OBJECT_ID",
                                              referencedColumnName = "ID",
                                              nullable = false)},
                   inverseJoinColumns = {@JoinColumn(name = "SPR_ID",
                                                     referencedColumnName = "ID",
                                                     nullable = false)})
        private List<OpSprOkved> okved_id_mult = new ArrayList<>();
}

和

@Entity
@Table(name = "SPI_V_OP_SPR_OKVED")
public class OpSprOkved extends PersistenceEntity implements Serializable {

    /** id */
    @Id
    @Column(name = "ID", nullable = false)
    private Long id;

    /** code*/
    @Column(name = "CODE")
    private String code;

    /** name*/
    @Column(name = "name")
    private String name;
}

属性 okved_id_mult 是多个。我想选择具有空属性 okved_id_mult 的对象 OpSubject_vr。

我试过

select ent from OpSubject_vr ent where okved_id_mult is empty; (hibernate error)

select ent from OpSubject_vr ent where okved_id_mult is null; (hibernate error)

select distinct ent from OpSubject_vr ent join ent.okved_id_mult i1 where i1.code is null;(return 0 objects)

Answer 1

1. 查询很好，但您需要将 okved_id_mult 限定为 ent.okved_id_mult。
2. 限制集合属性是非法的。
3. 您需要修改查询以使用左连接。那么它在逻辑上等价于第一个查询。

请参阅https://github.com/BatooOrg/BatooJPA/tree/master/community/src/test/java/org/batoo/jpa/community/test/t2上的测试用例

Answer 2

使用“not in”运算符。此查询将检查您的“okved_id_mult.id”是否未出现在所有现有的 OpSprOkved.id 中：

 select ent from OpSubject_vr ent where okved_id_mult.id not in
   ( select O.id from OpSprOkved O)