一：Hibernate實(shí)體對象的加載

比如說：用戶和訂單的關(guān)系是一對多，雖然它們有關(guān)聯(lián)，但是默認(rèn)是延遲加載Lazy=“true”，最終得到的是代理對象，如果要訪問代理對象的屬性的話，則會拋出異常，

解決方法：leftjoinfetch迫切抓取連接

selectufromUseruleftjoinfetchOrdero;

二：Hibernate普通屬性

默認(rèn)是：lazy=“false”

如果要改為延遲方法較麻煩

三：Hibernate集合對象

setlistmap默認(rèn)Lazy=“true”

1:List

Java代碼  
<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代碼  
<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代碼  
privateMapschool=newHashMap();  
 
publicMapgetSchool(){  
returnschool;  
}  
publicvoidsetSchool(Mapschool){  
this.school=school;  
}  
 
privateMapschool=newHashMap();  
 
publicMapgetSchool(){  
returnschool;  
}  
publicvoidsetSchool(Mapschool){  
this.school=school;  
} 

Xml代碼  
<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;  
} 

Xml代碼  
<mapnamemapname="school"table="schools"> 
<keycolumnkeycolumn="pid"not-null="true"/> 
<map-keytypemap-keytype="string"column="indet"/> 
<elementtypeelementtype="float"column="score"/> 
</map> 

key子元素用于映射外鍵列，而map-key子元素則用于映射Map集合的Key。

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5. Hibernate中hbm的generator屬性