Question

我有以下MySQL表。这里的想法是轨道和课程是主键。轨道中的课程可能取决于“相同轨道”中的另一门课程因此我在（track_id，depends_on_course_id）上创建了一个复合FK

CREATE  TABLE IF NOT EXISTS `testdb_1`.`track_course` (
`track_id` INT UNSIGNED NOT NULL ,
`course_id` INT UNSIGNED NOT NULL ,
`depends_on_course_id` INT UNSIGNED NULL ,
PRIMARY KEY (`track_id`, `course_id`) ,
INDEX `tc_tbl_dependent_crs_fk_idx` (`track_id` ASC, `depends_on_course_id` ASC) ,
CONSTRAINT `tc_tbl_dependent_crs_fk`
FOREIGN KEY (`track_id` , `depends_on_course_id` )
REFERENCES `testdb_1`.`track_course` (`track_id` , `course_id` ))

以下是由hibernate工具自动生成的类

@Entity
@Table(name = "track_course", catalog = "testdb_1")
public class TrackCourse implements java.io.Serializable {

    private TrackCourseId id;
    private TrackCourse trackCourse;
    private Set<TrackCourse> trackCourses = new HashSet<TrackCourse>(0);

    public TrackCourse() {
    }

    public TrackCourse(TrackCourseId id, TrackCourse trackCourse) {
        this.id = id;
        this.trackCourse = trackCourse;
    }

    public TrackCourse(TrackCourseId id, TrackCourse trackCourse,
            Set<TrackCourse> trackCourses) {
        this.id = id;
        this.trackCourse = trackCourse;
        this.trackCourses = trackCourses;
    }

    @EmbeddedId
    @AttributeOverrides({
            @AttributeOverride(name = "trackId", column = @Column(name = "track_id", nullable = false)),
            @AttributeOverride(name = "courseId", column = @Column(name = "course_id", nullable = false)) })
    public TrackCourseId getId() {
        return this.id;
    }

    public void setId(TrackCourseId id) {
        this.id = id;
    }

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumns({
            @JoinColumn(name = "track_id", referencedColumnName = "track_id", insertable = false, updatable = false),
            @JoinColumn(name = "depends_on_course_id", referencedColumnName = "course_id", insertable = false, updatable = false) })
    public TrackCourse getTrackCourse() {
        return this.trackCourse;
    }

    public void setTrackCourse(TrackCourse trackCourse) {
        this.trackCourse = trackCourse;
    }

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "trackCourse", cascade= CascadeType.ALL)
    public Set<TrackCourse> getTrackCourses() {
        return this.trackCourses;
    }

    public void setTrackCourses(Set<TrackCourse> trackCourses) {
        this.trackCourses = trackCourses;
    }

}

我正在尝试按如下方式写入此表。

TrackCourse tc1 = new TrackCourse(new TrackCourseId(11, 1), null);
TrackCourse tc2 = new TrackCourse(new TrackCourseId(11, 2), tc1);
TrackCourse tc4 = new TrackCourse(new TrackCourseId(11, 4), tc1);

Set<TrackCourse> trackCourses = new HashSet<TrackCourse>();
trackCourses.add(tc2);
trackCourses.add(tc4);
tc1.setTrackCourses(trackCourses);
session.save(tc1); // I expect this statement to create three rows with following values

track_id    course_id   depends_on_course_id
11,         1,          null
11          2           1
11          4           1

但是我在“depends_on_course_id列”中得到了所有null，我想getTrackCourse方法上的映射有问题但我无法弄清楚是什么？非常感谢任何帮助。

Answer 1

似乎getTrackCourse（）具有空cascadeType，因此默认情况下不会级联任何操作。

顺便说一下。我建议使用生成的键而不是自然键，这会使事情变得更复杂。

复合自引用Hibernate中的外键映射

1 个答案: