浅谈Hibernate中加载的三种类型
一：Hibernate实体对象的加载
比如说：用户和订单的关系是一对多，虽然它们有关联，但是默认是延迟加载Lazy=“true”，最终得到的是代理对象，如果要访问代理对象的属性的话，则会抛出异常，
解决方法：leftjoinfetch迫切抓取连接
selectufromUseruleftjoinfetchOrdero;
二：Hibernate普通属性
默认是：lazy=“false”
如果要改为延迟方法较麻烦
三：Hibernate集合对象
setlistmap默认Lazy=“true”
1:List
Java代码 <listnamelistname="diarys"table="petDiary"cascade="all"inverse="true"> <keycolumnkeycolumn="petId"></key> <indexcolumnindexcolumn="listindex"></index> <one-to-manyclassone-to-manyclass="com.lovo.po.PetDiary"/> </list> <listnamelistname="diarys"table="petDiary"cascade="all"inverse="true"> <keycolumnkeycolumn="petId"></key> <indexcolumnindexcolumn="listindex"></index> <one-to-manyclassone-to-manyclass="com.lovo.po.PetDiary"/> </list>
2:set
Java代码 <setnamesetname="orders" table="t_order" cascade="all" inverse="true" lazy="true" > <keycolumnkeycolumn="fk_customer_id"></key> <one-to-manyclassone-to-manyclass="Order"/> </set> <setnamesetname="orders" table="t_order" cascade="all" inverse="true" lazy="true" > <keycolumnkeycolumn="fk_customer_id"></key> <one-to-manyclassone-to-manyclass="Order"/> </set>
3:map
Java代码
privateMapschool=newHashMap();
publicMapgetSchool(){
returnschool;
}
publicvoidsetSchool(Mapschool){
this.school=school;
}
privateMapschool=newHashMap();
publicMapgetSchool(){
returnschool;
}
publicvoidsetSchool(Mapschool){
this.school=school;
} Xml代码
<mapnamemapname="school"table="schools">
<keycolumnkeycolumn="pid"not-null="true"/>
<map-keytypemap-keytype="string"column="indet"/>
<elementtypeelementtype="float"column="score"/>
</map>
privateMapschool=newHashMap();
publicMapgetSchool(){
returnschool;
}
publicvoidsetSchool(Mapschool){
this.school=school;
}
privateMapschool=newHashMap();
publicMapgetSchool(){
returnschool;
}
publicvoidsetSchool(Mapschool){
this.school=school;
}