默认情况下, Grails中多对多的映射是通过中间表来完成的. 以下面的多对多关联为例:class Group {
…
static hasMany = [people:Person]
}
class Person {
…
static belongsTo = Group
static hasMany = [groups:Group]
}在上面的例子中Grails将会创建一个 group_person 表包含外键 person_id 和 group_id 对应 person 和 group 表. 假如你需要改变列名，你可以为每个类指定一个列映射.class Group {
…
static mapping = {
people column:'Group_Person_Id'
}
}
class Person {
…
static mapping = {
groups column:'Group_Group_Id'
}
}你也可以指定中间表的名称:class Group {
…
static mapping = {
people column:'Group_Person_Id',joinTable:'PERSON_GROUP_ASSOCIATIONS'
}
}
class Person {
…
static mapping = {
groups column:'Group_Group_Id',joinTable:'PERSON_GROUP_ASSOCIATIONS'
}
}