Grails：如何在多对多的映射中查询对象？ [英] Grails: How to query objects in many to many mapping?

问题描述

  class Student {
 int age 
 static hasMany = [课程：课程] 
} 
 
课程{
字符串名称
 static hasMany = [学生：学生] 
} 
  

我想找到7岁的学生参加课程（ID为1）。

我可以使用动态查找器或条件构建器或HQL吗？

我不想做下面的事情，因为它会加载所有学生如此低效：

  def course = Course.get（1）; 
 course.students.findAll {it.age == 7} 
  

解决方案

  def studs = Student.withCriteria {
 eq（'age'，7）
 courses {
 eq（'id'， 1）
} 
} 
  

它位于 GORM doc ，查询关联部分。

Hello I have the follwing domain classes.

class Student {
   int age
   static hasMany = [courses:Course]
}

class Course {
   String name
   static hasMany = [students:Student]
}

I want to find the Students taking Course (with id 1), with age 7.

Could I do that with dynamic finder or criteria builder or HQL?

I do not want to do following as it load all students so inefficient:

def course = Course.get(1);
course.students.findAll{ it.age == 7 }

解决方案

def studs = Student.withCriteria {
  eq('age', 7)
  courses {
    eq('id', 1)
  }
}

It's in GORM doc, section "Querying Associations".

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