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一：Hibernate實(shí)體對(duì)象的加載

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比如說(shuō)：用戶和訂單的關(guān)系是一對(duì)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(duì)象，如果要訪問(wèn)代理對(duì)象的屬性的話，則會(huì)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(duì)象

setlistmap默認(rèn)Lazy=“true”

1:List

 
 
 

  
  
  
Java代碼 
  
  
  
<listnamelistname="diarys"table="petDiary"cascade="all"inverse="true">
  
  
  
<keycolumnkeycolumn="petId">
  
  
  
<indexcolumnindexcolumn="listindex">
  
  
  
<one-to-manyclassone-to-manyclass="com.lovo.po.PetDiary"/>
  
  
  

  
  
  

  
  
  
<listnamelistname="diarys"table="petDiary"cascade="all"inverse="true">
  
  
  
  <keycolumnkeycolumn="petId">
  
  
  
  <indexcolumnindexcolumn="listindex">
  
  
  
  <one-to-manyclassone-to-manyclass="com.lovo.po.PetDiary"/>
  
  
  

 
 
 

2:set

 
 
 

  
  
  
Java代碼 
  
  
  
<setnamesetname="orders"
  
  
  
table="t_order"
  
  
  
cascade="all"
  
  
  
inverse="true"
  
  
  
lazy="true"
  
  
  
>
  
  
  
<keycolumnkeycolumn="fk_customer_id">
  
  
  
<one-to-manyclassone-to-manyclass="Order"/>
  
  
  

  
  
  

  
  
  
<setnamesetname="orders"
  
  
  
table="t_order"
  
  
  
cascade="all"
  
  
  
inverse="true"
  
  
  
lazy="true"
  
  
  
>
  
  
  
<keycolumnkeycolumn="fk_customer_id">
  
  
  
<one-to-manyclassone-to-manyclass="Order"/>
  
  
  

 
 
 

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"/>
  
  
  

  
  
  

  
  
  
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"/>
  
  
  

 
 
 

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。

當(dāng)前文章：淺談Hibernate中加載的三種類型
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