Question

我在使用Hibernate中的@JoinColumnOrFormula检索嵌入式记录时遇到问题。

嵌入式：

    @Embeddable
    public class Location implements Serializable {

        @Id
        @Column(name = "loc_id")
        private String id;

        @Column(name = "loc_city")
        private String city;

        @Column(name = "loc_building")
        private String building;

        @Column(name = "loc_floor")
        private String floor;

        @Column(name = "loc_room")
        private String room;
    }

正在使用：

    @Entity
    @Table(name = "Persons")
    public class Person implements Serializable {

    ...
      @ManyToOne
      @JoinColumnsOrFormulas({
              @JoinColumnOrFormula(formula = @JoinFormula(value = "prs_loc_city", referencedColumnName = "loc_city")),
              @JoinColumnOrFormula(formula = @JoinFormula(value = "prs_loc_building", referencedColumnName = "loc_building")),
              @JoinColumnOrFormula(formula = @JoinFormula(value = "prs_loc_floor", referencedColumnName = "loc_floor")),
              @JoinColumnOrFormula(formula = @JoinFormula(value = "prs_loc_room", referencedColumnName = "loc_room"))})
      private Location location = new Location();

    ...
    }

生成正确的Oracle SQL以检索人员的位置：

    SELECT
    ...
           FROM PERSONS this_
           LEFT OUTER JOIN LOCATIONS location_
              ON this_.prs_loc_city = location_.loc_city
                 AND this_.prs_loc_building = location_.loc_building
                 AND this_.prs_loc_floor = location_.loc_floor
                 AND this_.prs_loc_room = location_.loc_room

但是，这适用于提供所有四列的所有情况。列prs_loc_room为空（null）的人不会从Locations表中检索相应的记录，尽管它存在（loc_room为null）。

正确的SQL工作方式如下：

    SELECT
    ...
           FROM PERSONS this_
           LEFT OUTER JOIN LOCATIONS location_
              ON NVL(this_.prs_loc_city, 'null') = NVL(location_.loc_city, 'null')
                 AND NVL(this_.prs_loc_building, 'null') = NVL(location_.loc_building, 'null')
                 AND NVL(this_.prs_loc_floor, 'null') = NVL(location_.loc_floor, 'null')
                 AND NVL(this_.prs_loc_room, 'null') = NVL(location_.loc_room, 'null')

但是如何使用Hibernate达到这个目标？

Hibernate @JoinColumnOrFormula比较空值

0 个答案: