Hibernate通过java注释将java中的嵌套集合映射到映射表？

发布于 2024-09-25 16:37:22 字数 666 浏览 4 评论 0原文

我在使用 java 注释编写 hibernate 映射来解决问题时遇到困难，如下所示。

问题：

表格

Table:Courses_Teachers
columns:
id
course_id
teacher_id
year(academic year)

Table: Courses_Students
columns:
id
course_id
student_id
year(academic year)

Table: Courses_Teachers_Students
course_teacher_id
course_student_id

课程

class Student {
    Map<Course,List<Teacher>> courseTeachersMap;  
}

要求

一门课程可以由多名教师向同一学生组教授。
一门课程被分配到一个年级。
一个年级可以有多个学生组，为课程分配不同的教师组。

请建议我如何在学生班级中为 courseTeachersMap 属性指定注释。

原文

I am facing difficulty to write hibernate mapping with java annotation for problem as given below.

Problem:

Tables

Table:Courses_Teachers
columns:
id
course_id
teacher_id
year(academic year)

Table: Courses_Students
columns:
id
course_id
student_id
year(academic year)

Table: Courses_Teachers_Students
course_teacher_id
course_student_id

Classes

class Student {
    Map<Course,List<Teacher>> courseTeachersMap;  
}

Requirements

A course can be taught by multiple teachers to same student group .
A course is assigned to a grade level.
A grade level can have multiple student groups who are assigned different set of teachers for a course.

Please suggest me how to specify annotation for courseTeachersMap property in class student.

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如果没结果 2024-10-02 16:37:22

可以使用 Map 映射 ManyToMany 关联，这种映射的典型用例是当您具有三元关联时。例如，如果您有：

STUDENT_TEACHER_COURSE
STUDENT_ID(FK, PK)
TEACHER_ID(FK, PK)
COURSE_ID (FK, PK)

那么您可以定义以下映射（假设您使用的是 Hibernate Annotations <3.5）：

@Entity
public class Student {
    ...
    @ManyToMany
    @JoinTable(
        name="STUDENT_TEACHER_COURSE", 
        joinColumns= { @JoinColumn(name="STUDENT_ID") },
        inverseJoinColumns= { @JoinColumn(name="TEACHER_ID") }
    )
    @MapKeyManyToMany(joinColumns = @JoinColumn(name="COURSE_ID",unique = false))
    protected Map<Course,Teacher> teachers ;
    ...
}

但是我认为您不能有一个“嵌套”List; 作为 Map 内的值，我认为 Hibernate 无法映射它，我会考虑从实体获取 List 。

参考资料

Hibernate Annotations 3.4 参考指南
- 2.4.6.2 .2.地图
Hibernate 注解 3.5 参考指南
- 2.2.5.3 .4.索引集合（列表、地图）

资源

It is possible to map a ManyToMany association using a Map, and a typicall use case for this kind of mapping is when you have a ternary association. For example, if you have:

STUDENT_TEACHER_COURSE
STUDENT_ID(FK, PK)
TEACHER_ID(FK, PK)
COURSE_ID (FK, PK)

Then you could define the following mapping (assuming you're using a Hibernate Annotations < 3.5):

@Entity
public class Student {
    ...
    @ManyToMany
    @JoinTable(
        name="STUDENT_TEACHER_COURSE", 
        joinColumns= { @JoinColumn(name="STUDENT_ID") },
        inverseJoinColumns= { @JoinColumn(name="TEACHER_ID") }
    )
    @MapKeyManyToMany(joinColumns = @JoinColumn(name="COURSE_ID",unique = false))
    protected Map<Course,Teacher> teachers ;
    ...
}

But I don't think you can have a "nested" List<Teacher> as value inside the Map, I don't think Hibernate can map that and I'd consider getting the List from an entity instead.