Hibernate Grails—将多对多父/子关系映射到单个联接表
我的问题基于以下(简化的)Grails域类Hibernate Grails—将多对多父/子关系映射到单个联接表,hibernate,grails,groovy,nhibernate-mapping,gorm,Hibernate,Grails,Groovy,Nhibernate Mapping,Gorm,我的问题基于以下(简化的)Grails域类 class Dimension { String name static hasMany = [ children: Dimension, parents: Dimension ] } 有没有办法将多对多父/子关系映射到单个联接表?据我所知,唯一的方法是创建另一个表示父-子关系的域类 class DimensionDependency { Dimension parent Dimen
class Dimension {
String name
static hasMany = [
children: Dimension,
parents: Dimension
]
}
有没有办法将多对多父/子关系映射到单个联接表?据我所知,唯一的方法是创建另一个表示父-子关系的域类
class DimensionDependency {
Dimension parent
Dimension child
static belongsTo = Dimension
}
class Dimension {
static hasMany = [parentDependencies: DimensionDependency]
static mappedBy = [parentDependencies: 'child']
static mapping = { parentDependencies cascade: 'all-delete-orphan' }
}
mappedBy
关键字指定引用DimensionDependency
的对象始终是子对象。通过在映射中指定all delete orphan
,我们可以确保在从子级删除parentDependency
时,关联的DimensionDependency
会从数据库中删除
您还可以向维度
类添加方便的方法,以封装维度依赖项
上的操作,使接口更像GORM
static transients = ['children', 'parents']
Set<Dimension> getChildren()
{
AssignmentDependency.findAllByParent(this).child
}
Set<Dimension> getParents()
{
parentDependencies?.parent ?: []
}
Dimension addToParents(Dimension parent)
{
if (!parentDependencies.find { it.parent == parent && it.child == this })
{
addToParentDependencies(new DimensionDependency(parent: parent, child: this))
}
return this
}
Dimension removeFromParents(Dimension parent)
{
def dep = parentDependencies.find { it.parent == parent }
removeFromParentDependencies(dep)
dep.delete(flush: true)
return this
}
static transients=['children','parent']
Set getChildren()
{
AssignmentDependency.findAllByParent(this).child
}
设置getParents()
{
父依赖项?.parent?:[]
}
维度addToParents(维度父级)
{
如果(!parentDependencies.find{it.parent==parent&&it.child==this})
{
addToParentDependencies(新维度相关性(父:父,子:此))
}
还这个
}
维度从父维度移除(维度父维度)
{
def dep=parentDependencies.find{it.parent==parent}
removeFromParentDependencies(dep)
副删除(刷新:真)
还这个
}
我已经使用这种方法一段时间了,到目前为止还没有遇到任何问题