grails - 如何保持多对多关系的秩序

Question

我的项目要求我保持多对多关系的插入和检索顺序。默认情况下，groovy将元素保存为多对多关系中的Set。我想在 list 中做。我不确定如何更新关系以使用List而不是Set。任何帮助，将不胜感激。

class Course{
        static belongsTo = Teacher
        static hasMany = [teacher:Teacher]

        static mapping = {
            teacher joinTable : [name: TeacherCourse]
        }
    }

    class Teacher{

        static hasMany = [course:Course]
        static mapping = {
            course joinTable : [name: TeacherCourse]
        }
    }

在Teacher或Course上调用save()还会在TeacherCourse表中插入新行。它没有问题。在数据库中，表为:
老师(PK:Id)
类(class)(PK:Id)
TeacherCourse(PK:[Teacher_id，Course_id])

有没有一种方法可以维持多对多关系中的插入和检索顺序？

谢谢..

编辑
在 Controller 中save()

def courseInstance = new Course()
List <Teacher> teacherList= []
teacherList.add(Teacher.findById(65))
teacherList.add(Teacher.findById(36))
courseInstance.courseUnits = teacherList
courseInstance.save(flush:true)

Answer 1

试试这个:

class Course {
    List teachers

    static belongsTo = Teacher
    static hasMany = [teachers:Teacher]

    static mapping = {
        teachers joinTable : [name: TeacherCourse]
    }
}

class Teacher {
    List courses

    static hasMany = [courses:Course]
    static mapping = {
        courses joinTable : [name: TeacherCourse]
    }
}

Reference