在hibernate中使用复合主键持久保存1-M个实体

Question

我有以下100万个实体的关系，指导学生。mentor有复合主键，我在student中使用它作为外键

@Entity
public class Mentor implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    private MentorPK id;
    private String email;
    @OneToMany(mappedBy="mentor")
    private Set<Student> students;

    public MentorPK getId() {
        return id;
    }            
    //getters and setters
}

@Embeddable
public class MentorPK implements Serializable {

    private static final long serialVersionUID = 1L;
    private String name;
    private String add;
    //getters and setters
    //override equals and hashcode
}


@Entity
public class Student implements Serializable{
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String name;    

    @ManyToOne
    @MapsId("id")
    @JoinColumns({
        @JoinColumn(name="name_fk", referencedColumnName="name"),
        @JoinColumn(name="address_fk", referencedColumnName="address")
    })
    private Mentor mentor;

    //Getters and setters
}

然后，我将上面的内容保持为下面的内容，但在student表为空的地方，只有mentor被保持。

我如何坚持与学生的导师？

Set<Student> students = new HashSet<Student>();

Student s1 = new Student();
s1.setName("Student 1");

Student s2 = new Student();
s2.setName("Student 2");

students.add(s1);
students.add(s2);

MentorPK mpk = new MentorPK();
mpk.setAddress("C");
mpk.setName("D");

Mentor m = new Mentor();
m.setId(mpk);
m.setEmail("emaill");
m.setStudents(students);

studentManager.saveMentor(m);

Answer 1

尝试将students字段的注释更改为

@OneTomany(MappedBy=“Mentor”,cascade=CascadeType.Persist)