休眠一对多关系：一旦父母被移除就无法移除孩子

Question

我有一个课程评论一对多的关系。在课程表中有 id 和 title 列。在 Review 表中有 id、comment 和 course_id，其中“course_id”作为 FK 指向 Course id。我想实现这样的场景，一旦课程被删除，相关的评论就会被自动删除。我有以下代码：

@Entity

@Table(name = "course")

public class Course {

    @Id

    @GeneratedValue(strategy = GenerationType.IDENTITY)

    @Column(name = "id")

    private int id;

    @Column(name = "title")

    private String title;

    @OneToMany(mappedBy = "course", fetch = FetchType.LAZY, cascade = CascadeType.ALL, orphanRemoval = true)

    private List<Review> reviews;

    public void addReview(Review review){

        if(reviews==null) reviews = new ArrayList<>();

        reviews.add(review);

    }

    //other codes below omitted

}

@Entity

@Table(name = "review")

public class Review {

    @Id

    @GeneratedValue(strategy = GenerationType.IDENTITY)

    @Column(name = "id")

    private int id;

    @Column(name = "comment")

    private String comment;

    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)

    @JoinColumn(name = "course_id")

    private Course course;

//other codes omitted

}

Answer 1

您的评论从未真正属于该课程，因为您从未初始化关联的拥有部分：Review.course。将您的addReview()方法更改为@OneToMany(mappedBy = "course", fetch = FetchType.LAZY, cascade = CascadeType.ALL, orphanRemoval = true)private List<Review> reviews = new ArrayList<>();public void addReview(Review review){&nbsp; &nbsp; review.setCourse(this);&nbsp; &nbsp; reviews.add(review);}