java - 保存父对象后自动保存子对象

Question

我已经看过了 - Save child objects automatically using JPA Hibernate

Hibernate: OneToMany save children by cascade

我有以下表格 -

• Instructor_Detail(id、youtubechannel、爱好)- PRIMARY_KEY (id)
• 讲师(id、名字、姓氏、电子邮件、讲师详细信息 ID)-PRIMARY_KEY (id)、FOREIGN_KEY (instructor_detail_id)
• 类(class)(id、标题、instructor_id)- PRIMARY_KEY (id)、FOREIGN_KEY(instructor_id)

我正在尝试在我的 MainApp 中保存(instructorDetail)，并期望自动保存关联的讲师和类(class)

这是我的类(class) -

<p></p>

@Entity
@Table(name="instructor_detail")
public class InstructorDetail { 
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="id")
    private int id;

    @Column(name="youtube_channel")
    private String youtubeChannel;

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

    @OneToOne(mappedBy = "instructorDetail", cascade= {
            CascadeType.DETACH,CascadeType.MERGE,CascadeType.PERSIST,CascadeType.REFRESH
    })
    private Instructor instructor;
    //getters and setters
}

@Entity
@Table(name="instructor")
public class Instructor {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="id")
    private int id;

    @Column(name="first_name")
    private String firstName;

    @Column(name="last_name")
    private String lastName;

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

    @OneToOne(cascade=CascadeType.ALL)
    @JoinColumn(name="instructor_detail_id")
    private InstructorDetail instructorDetail;

    @OneToMany(mappedBy="instructor",
            cascade = 
        {CascadeType.DETACH,CascadeType.MERGE,CascadeType.PERSIST,CascadeType.REFRESH})
    private List<Course> courses;

//...getters and setters

//one more method to add courses
public void addCourse(Course c) {
        if(courses == null) {
            courses = new ArrayList<>();
        }
        courses.add(c);
        c.setInstructor(this);
    }
}

@Entity
@Table(name="course")
public class Course {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="id")
    private int id;

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

    @ManyToOne(cascade= 
        {CascadeType.DETACH,CascadeType.MERGE,CascadeType.PERSIST,CascadeType.REFRESH})
    @JoinColumn(name="instructor_id")
    private Instructor instructor;

//getters and setters
}

//MainClass -
public class OneToManyBiDirectionalDemo {

    public static void main(String[] args) {
        Course c1 = new Course("Multithreading");
        Course c2 = new Course("WebDevelopment");
        Instructor ins1 = new Instructor("John","Purcell","john.purcell@email.com");
        InstructorDetail insDet1 = new InstructorDetail("com.john.purcell","teaching");

        insDet1.setInstructor(ins1);
        ins1.setInstructorDetail(insDet1);

        ins1.addCourse(c1);
        ins1.addCourse(c2);

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

        Session session = factory.getCurrentSession();
        session.beginTransaction();
        session.save(insDet1);
        session.getTransaction().commit();
        session.close();
        factory.close();    
    }
}

我的期望是 - 当在 MainClass 中调用 save(instructorDetail) 时，讲师和类(class)也应该自动保存。但是，执行当前仅保存讲师详细信息，而不保存讲师和类(class)。日志中仅触发一次插入，并且不会生成异常。我是 Hibernate 的新手，所以我的期望或理解可能会有所偏差。但这可能吗？

Answer 1

JPA CascadeType您配置的( DETACH 、 MERGE 、 PERSIST 、 REFRESH )仅在与 Session 一起使用时具有级联效果的evict() , merge() , persist() , refresh() 。 (参见this)

但是您正在使用 session.save()用于保存对象。这就是为什么它没有任何级联效果。更改为以下任一内容应该可以解决问题:

(1) 全部更改 CascadeType至ALL .

(2) 使用session.persist()插入记录:

  session.persist(insDet1);