Hibernate/JPA单向OneToMany,在源表中具有常量值的连接条件

Question

我想使用Hibernate注释来表示使用连接的单向一对多关系.我想在连接上添加一个条件,这样只有当源表中的列("一")等于一个常量值时才会发生这种情况.例如.

SELECT *
FROM buildings b
LEFT JOIN building_floors bf on bf.building_id = b.id AND b.type = 'OFFICE'

我想表示该b.type = 'OFFICE'查询的一部分.

我的问题与此问题非常相似,只是我在源表上有条件.JPA/Hibernate加入恒定价值

Java实体看起来像这样:

@Entity
@Table(name = "buildings")
public class Building {

    @Id
    @Column(name = "id")
    private int id;

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

    @OneToMany(mappedBy = "buildingId",
            fetch = FetchType.EAGER,
            cascade = {CascadeType.ALL},
            orphanRemoval = true)
    @Fetch(FetchMode.JOIN)
    // buildings.type = 'OFFICE'   ????
    private Set<BuildingFloors> buildingFloors;

    // getters/setters
}

@Entity
@Table(name = "building_floors")
public class BuildingFloor {

    @Id
    @Column(name = "building_id")
    private int buildingId;

    @Id
    @Column(name = "floor_id")
    private int floorId;

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

    // getters/setters
}

我尝试了一些我有占位符评论的东西:

@Where注释

这不起作用,因为它适用于目标实体.

@JoinColumns注释

@JoinColumns({
        @JoinColumn(name = "building_id", referencedColumnName = "id"),
        @JoinColumn(name = "'OFFICE'", referencedColumnName = "type")
})

这不起作用,因为我得到以下错误(为简洁起见,简化): Syntax error in SQL statement "SELECT * FROM buildings b JOIN building_floors bf on bf.building_id = b.id AND bf.'OFFICE' = b.type"

一个不同的@JoinColumns注释

@JoinColumns({
        @JoinColumn(name = "building_id", referencedColumnName = "id"),
        @JoinColumn(name = "buildings.type", referencedColumnName = "'OFFICE'")
})

这不起作用,因为在使用单向OneToMany关系时,referencedColumnName来自源表.所以我得到错误:org.hibernate.MappingException: Unable to find column with logical name: 'OFFICE' in buildings

提前致谢!

Answer 1

为什么不使用继承？(我用JPA,我从不直接使用hibernate)

@Entity
@Inheritance
@Table(name = "buildings")
@DiscriminatorColumn(name="type")
public class Building {

    @Id
    @Column(name = "id")
    private int id;

    @Column(name = "type")
    private String type;
}

而且:

@Entity
@DiscriminatorValue("OFFICE")
public class Office extends Building {
    @OneToMany(mappedBy = "buildingId",
        fetch = FetchType.EAGER,
        cascade = {CascadeType.ALL},
        orphanRemoval = true)
    private Set<BuildingFloors> buildingFloors;
}