hibernate组件映射
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1 对象关系:一个对象是另外一个对象的一部分
2 数据库表:一张表
3 annotation: @ Embeddable @Embbeded
对象模型
Husband(id,name,wife)
Wife(name,age)
Annotation:
在Husband的wife属性上建立注解
@Embedded表明该对象是从别的位置嵌入过来的,是不需要单独映射的表.
这种方式生成的表为husband(id,name,wifename,wifeage),不会生成wife表.
@Embedded
Public WiftgetWife(){
}
@AttributeOverride注解需要写在getWife方法上,可以重新指定生成的Wife类组件生成的字段名,例如:Husband与Wife两个类中都有name字段,这样在生成表的时候会有冲突,此时采用@AttributeOverride注解可以指定Wife类中的name属性对应新的字段名—“wifename”,不过@AttributeOverride注解不常用,
因为有更好的解决方法.
1:不要在组件的两个映射类中写同名属性;
2:如果真的有重复,那么可以在分类中(此处为Wife类)的重复名称的属性上使用如下内容以指定新的字段名:
@Column(name="wifename")
public String getName() {
return name;
}
另外,@ Embeddable注解好像是写在分类(Wife类)的类名前的,不过好像不写也行
@Embeddable
publicclass Wife {… …}
4 xml:使用<component,例如:
<class name="Husband" >
<idname="id">
<generatorclass="native"/>
</id>
<propertyname="name"></property>
<componentname="wife">
<propertyname="wifeName"/>
<propertyname="wifeAge"/>
</component>
</class>
例子:
create table Husband(
id integer not null auto_increment,
name varchar(255),
age integer not null,
wiftName varchar(255),
primary key (id)
)
package com.bjsxt.hibernate;
import javax.persistence.Embedded;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinColumns;
import javax.persistence.OneToOne;
@Entity
public class Husband {
private int id;
private String name;
private Wife wife;
@Id
@GeneratedValue
public int getId() {
return id;
}
public String getName() {
return name;
}
@Embedded
public Wife getWife() {
return wife;
}
public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public void setWife(Wife wife) {
this.wife = wife;
}
}
package com.bjsxt.hibernate;
public class Wife {
private String wifeName;
private int age;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getWifeName() {
return wifeName;
}
public void setWifeName(String name) {
this.wifeName = name;
}
}
--xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.bjsxt.hibernate.Husband" >
<id name="id">
<generator class="native"></generator>
</id>
<property name="name"></property>
<component name="wife">
<property name="wifeName"></property>
<property name="age"></property>
</component>
</class>
</hibernate-mapping>
hibernate.cfg.xml
<mapping resource="com/bjsxt/hibernate/Husband.hbm.xml"/>
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