<!-- [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]-->
继承映射
Animal 表
|
Id |
name |
Sex |
Weight |
Height |
Type |
|
1 |
小猪 |
True |
100 |
|
P |
|
2 |
小鸟 |
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" );
}
当用 Pig 去加载时是可以的，用父类 Animal 去加载也可以，但是 load 默认是 lazy 加载，用 Animal 加载的是 animal 代理类不是真正的 Pig 类
如果你把 class 中的 lazy=”false”, 则用 Animal 加载的是是真正的 Pig 类（多态）
用 get() 方法和 sql 查询支持多态查询，返回的是真正的 Pig 类
Sql 的“ from java.lang.Object ”是查到所有的实体类对象；
2 每个类一张映射表
animal 表
|
Id |
Name |
sex |
|
1 |
小猪 |
True |
|
2 |
小鸟 |
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 >
这种对象模型不变而存储模型的方法变了；缺点是建表多，效率低；
如果 User 对象的一些属性也是其他对象的属性（即他们有许多共同的属性），因此将共同的属性提取成为一个公用的类（此类包含了共同的属性）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 >
对关系模型没有任何影响，这样适合复用；
复合主键映射
通常将复合主键相关的属性放到一个单独的类中，这个是有约束的：
l 必须实现序列化接口
l 必须写 hashCode() 和 equals()
public class User {
private int age ;
private PK composite ;// 复合主键
}
//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 |
