<!-- [if !mso]> <style> v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} </style> <![endif]--><!-- [if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:DrawingGridVerticalSpacing>7.8 磅</w:DrawingGridVerticalSpacing> <w:DisplayHorizontalDrawingGridEvery>0</w:DisplayHorizontalDrawingGridEvery> <w:DisplayVerticalDrawingGridEvery>2</w:DisplayVerticalDrawingGridEvery> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:SpaceForUL/> <w:BalanceSingleByteDoubleByteWidth/> <w:DoNotLeaveBackslashAlone/> <w:ULTrailSpace/> <w:DoNotExpandShiftReturn/> <w:AdjustLineHeightInTable/> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:UseFELayout/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!-- [if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!-- [if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:普通表格; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--><!-- [if gte mso 9]><xml> <o:shapedefaults v:ext="edit" spidmax="1030"/> </xml><![endif]--><!-- [if gte mso 9]><xml> <o:shapelayout v:ext="edit"> <o:idmap v:ext="edit" data="1"/> </o:shapelayout></xml><![endif]-->
繼承映射
Animal 表
|
Id |
name |
Sex |
Weight |
Height |
Type |
|
1 |
小豬 |
True |
100 |
? |
P |
|
2 |
小鳥 |
False |
? |
20 |
B |
Extends.hbm.xml 如下：
< hibernate-mapping package = "com.test.hibernate" >
??? < class name = "Animal" table = "animal" >
?????? < id name = "id" >
?????????? < generator class = "native" ></ generator >
?????? </ id >
??? ??? < property name = "name" ></ property >
?????? < property name = "sex" ></ property >
?????? < discriminator column = "type" type = "string" />
?????? < subclass name = "Pig" discriminator-value = "P" >
?????????? < property name = "weight" ></ property >
?????? </ subclass >
?????? < subclass name = "Bird" discriminator-value = "B" >
?????????? < property name = "height" ></ property >
?????? </ subclass >
??? </ class >
</ hibernate-mapping >
?
Animal animal =(Animal)session.load(animal.Class, 1);
?????? if (animal instanceof Pig) {
?????????? System. out .println( "Pig" );
??????????
?????? }
?
當用 Pig 去加載時是可以的，用父類 Animal 去加載也可以，但是 load 默認是 lazy 加載，用 Animal 加載的是 animal 代理類不是真正的 Pig 類
如果你把 class 中的 lazy=”false”, 則用 Animal 加載的是是真正的 Pig 類（多態）
用 get() 方法和 sql 查詢支持多態查詢，返回的是真正的 Pig 類
Sql 的“ from java.lang.Object ”是查到所有的實體類對象；
2 每個類一張映射表
animal 表
|
Id |
Name |
sex |
|
1 |
小豬 |
True |
|
2 |
小鳥 |
false |
? pig 表
|
pid |
weight |
|
1 |
100 |
bird 表
|
bid |
height |
|
1 |
10 |
Extends.hbm.xml 如下：
< hibernate-mapping package = "com.test.hibernate" >
??? < class name = "Animal" table = "animal" >
?????? < id name = "id" >
?????????? < generator class = "native" ></ generator >
?????? </ id >
?????? < property name = "name" ></ property >
?????? < property name = "sex" ></ property >
?????? <join- subclass name = "Pig" table=”pig” >
?????????? <key column=”pid” />
?????????? < property name = "weight" ></ property >
?????? </ join- subclass >
?????? < join- subclass name = "Bird" table=”bird” >
?????????? <key column=”bid” />
?????????? < property name = "height" ></ property >
?????? </ join- subclass >
??? </ class >
這種對象模型不變而存儲模型的方法變了；缺點是建表多，效率低；
如果 User 對象的一些屬性也是其他對象的屬性（即他們有許多共同的屬性），因此將共同的屬性提取成為一個公用的類（此類包含了共同的屬性）如：
public class User {
??? private int id ;
??? private Contact conta ct ;
?
}
//set,get 方法略
public class Contact {
private String name ;
private boolean sex ;
}
//set,get 方法略
User.hbm.xml 如下：
< hibernate-mapping package = "com.test.hibernate" >
??? < class name = "User" table = "user" >
?????? < id name = "id" >
?????????? < generator class = "native" ></ generator >
?????? </ id >
?????? <component name= "contact">
?????????? < property name = "name" ></ property >
?????? ??? < property name = "sex" ></ property >
?????? </component>
??? </ class >
對關系模型沒有任何影響，這樣適合復用；
復合主鍵映射
通常將復合主鍵相關的屬性放到一個單獨的類中，這個是有約束的：
l ?????? 必須實現序列化接口
l ?????? 必須寫 hashCode() 和 equals()
public class User {
??? private int age ;
??? private PK composite ;// 復合主鍵
?
}
//set,get 方法略
public class PK {
private String name ;
private boolean sex ;
}
//set,get 方法略
User.hbm.xml 如下：
< hibernate-mapping package = "com.test.hibernate" >
??? < class name = "User" table = "user" >
?????? <composite-id name= " composite ">
?????? ??? <key- property name = "name" ></key- property >
?????? ??? <key- property name = "sex" ></key- property >
</composite-id>
< property name = "name" ></ property >
?????? ??? </ class >
集合的映射
t_collection_mapping 表
|
|
name |
|
1 |
xxx |
t_set_values 表
|
set_id |
set_value |
|
1 |
A |
|
1 |
b |
t_list_values 表
|
list_id |
list_value |
list_index |
|
1 |
c |
0 |
|
1 |
d |
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