Question

我有一个课程复习一对多关系。在“课程”表中，有id和title列。在“评论”表中，有id，注释和带有“ course_id”的Course_id，FK指向课程ID。我想知道这样的情况：课程一经删除，相关的评论应自动删除。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
}

客户代码：

public class Client_OneToMany_bidirectional {
    public static void main(String[] args) {

        SessionFactory sf = new Configuration()
                .configure("hibernate.cfg.xml")
                .addAnnotatedClass(Instructor.class)
                .addAnnotatedClass(InstructorDetail.class)
                .addAnnotatedClass(Course.class)
                .addAnnotatedClass(Review.class)
                .buildSessionFactory();

        Session session = sf.getCurrentSession();

        try{
            //add course and review
            Course course = new Course("How to learn Java");

            course.addReview(new Review("Good course!"));
            course.addReview(new Review("I love it!"));
            course.addReview(new Review("Need some more!"));

            session.beginTransaction();
            System.out.println(course);
            System.out.println(course.getReviews());
            session.save(course);
            session.getTransaction().commit();

            //start to delete the course
            session = sf.getCurrentSession();
            session.beginTransaction();
            Course crs = session.get(Course.class, 12);
            if(crs != null ){
                session.delete(crs);
            }
            session.getTransaction().commit();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            session.close();
            sf.close();
        }
    }
}

我发现我可以成功删除该课程，但未删除这三个评论。在搜索与stackoverflow相关的帖子之后，我还尝试使用orphanRemoval = true，但仍然无法正常工作。

Answer 1

由于您从未初始化关联的拥有部分：sh "curl -0 https://url.com/path1/somefile.1 curl -0 https://url.com/path2/somefile.2 curl -0 https://url.com/path3/somefile.3 aws s3 copy ./somefile.1 s3:bucket aws s3 copy ./somefile.2 s3:bucket aws s3 copy ./somefile.3 s3:bucket"，因此您的评论永远不会真正属于该表述。将您的Review.course方法更改为

addReview()

休眠一对多关系：移除父母后就无法移除孩子

1 个答案: