我有几个域类，用户界面包括
“重复”命令。作为执行这些命令的一部分，
我已经在相应的域类中实现了clone() 方法。
我一直在努力改正我执行不当的坏习惯
clone()（通常）基于使用“new”而不是"super.clone(),"
所以一旦我想到对我的 Grails 域做同样的事情
类，我想知道如何使用super.clone() 获取克隆可能
与GORM/Hibernate 持久化交互。特别是，我是
想知道处理隐式“id”属性的正确方法。如果
我只是super.clone()，什么都不做，以后试试save()
克隆的实例，它会正常工作吗（创建一个新的持久性
条目？）还是会导致某种错误或静默失败？
复制 Grails 域的正确或首选方法是什么 实例？
【问题讨论】：
标签： grails clone grails-orm
将以下方法添加到接口GormInstanceApi的元类中，所有域都实现了它。
：
def cloneForDomains={def cloned=delegate.class.newInstance();
cloned.properties=delegate.properties;
return cloned;}
然后：
org.grails.datastore.gorm.GormInstanceApi.clone=cloneForDomains ;
恭喜！现在您可以使用clone 方法，例如save，delete .....
用例：
Person p=Person.get(1);
Person cloned=p.clone();
cloned.id=null;
cloned.save();
更新：您也可以循环所有域类：
grailsApplication.getDomainClasses().each{cls->
cls.metaClass.clone=cloneForDomains
}
更新： 用于深度克隆：
grailsApplication.getDomainClasses().each{cls->
cls.metaClass.clone={
return deepClone(delegate);
}
}
知道deepClone是一个方法如下：
Object deepClone(domainInstanceToClone) {
//TODO: PRECISA ENTENDER ISSO! MB-249 no youtrack
//Algumas classes chegam aqui com nome da classe + _$$_javassist_XX
if (domainInstanceToClone.getClass().name.contains("_javassist"))
return null
//Our target instance for the instance we want to clone
// recursion
def newDomainInstance = domainInstanceToClone.getClass().newInstance()
//Returns a DefaultGrailsDomainClass (as interface GrailsDomainClass) for inspecting properties
GrailsClass domainClass = domainInstanceToClone.domainClass.grailsApplication.getDomainClass(newDomainInstance.getClass().name)
def notCloneable = domainClass.getPropertyValue("notCloneable")
for(DefaultGrailsDomainClassProperty prop in domainClass?.getPersistentProperties()) {
if (notCloneable && prop.name in notCloneable)
continue
if (prop.association) {
if (prop.owningSide) {
//we have to deep clone owned associations
if (prop.oneToOne) {
def newAssociationInstance = deepClone(domainInstanceToClone?."${prop.name}")
newDomainInstance."${prop.name}" = newAssociationInstance
} else {
domainInstanceToClone."${prop.name}".each { associationInstance ->
def newAssociationInstance = deepClone(associationInstance)
if (newAssociationInstance)
newDomainInstance."addTo${prop.name.capitalize()}"(newAssociationInstance)
}
}
} else {
if (!prop.bidirectional) {
//If the association isn't owned or the owner, then we can just do a shallow copy of the reference.
newDomainInstance."${prop.name}" = domainInstanceToClone."${prop.name}"
}
// @@JR
// Yes bidirectional and not owning. E.g. clone Report, belongsTo Organisation which hasMany
// manyToOne. Just add to the owning objects collection.
else {
//println "${prop.owningSide} - ${prop.name} - ${prop.oneToMany}"
//return
if (prop.manyToOne) {
newDomainInstance."${prop.name}" = domainInstanceToClone."${prop.name}"
def owningInstance = domainInstanceToClone."${prop.name}"
// Need to find the collection.
String otherSide = prop.otherSide.name.capitalize()
//println otherSide
//owningInstance."addTo${otherSide}"(newDomainInstance)
}
else if (prop.manyToMany) {
//newDomainInstance."${prop.name}" = [] as Set
domainInstanceToClone."${prop.name}".each {
//newDomainInstance."${prop.name}".add(it)
}
}
else if (prop.oneToMany) {
domainInstanceToClone."${prop.name}".each { associationInstance ->
def newAssociationInstance = deepClone(associationInstance)
newDomainInstance."addTo${prop.name.capitalize()}"(newAssociationInstance)
}
}
}
}
} else {
//If the property isn't an association then simply copy the value
newDomainInstance."${prop.name}" = domainInstanceToClone."${prop.name}"
if (prop.name == "dateCreated" || prop.name == "lastUpdated") {
newDomainInstance."${prop.name}" = null
}
}
}
return newDomainInstance
}
【讨论】：
这种方法让我更幸运：
YourDomainClass clonedObject = new YourDomainClass(objectToClone.properties)
【讨论】：