@Embeddable 中的 JPA @ElementCollection

Question

@Entity
public class School {
 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer schoolId;
...
 @ElementCollection
 @CollectionTable(
            name = "grades",
            joinColumns = @JoinColumn(name = "schoolId")
    )
 private Set<Grade> grades;

}
----------------------------------

@Embeddable
public class Grade {

private int gradeId

@ElementCollection
@CollectionTable(
            name = "Class",
            joinColumns = @JoinColumn(name = "gradeId")
    )
    private Set<Class> classes;

}


------------------------------------

@Embeddable
public class Class {

private int numOfStudent
private int female;
private int mamle;

}

我想要获取映射表。但是，出现此错误。

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Property 'com.School.grades.collection&&element.clases' belongs to an '@Embeddable' class that is contained in an '@ElementCollection' and may not be a '@ElementCollection'

我不确定上面的代码是否正确。我可以做什么来修复这个错误？

尝试使用@secondrytable和@AttributeOverride。 但是..找不到解决方案。

Answer 1

集合表没有自己的主键。因此，一个元素集合不能包含在另一个元素集合中。我认为至少类

Grade

具有标识符

gradeId

，您可以将其设为通常的

@Entity

并将

grades

字段映射从

@ElementCollection

更改为

@OneToMany

。