Model
public class User { //多
private Integer id;
private String name;
private Group group;
}
public class Group { //一
private Integer id;
private String name;
}
hbm.xml
user.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.model">
<class name="User" table="user1" >
<id name="id" column="user_id" type="java.lang.Integer">
<generator class="native" />
</id>
<property name="name" length="50" type="java.lang.String" />
<many-to-one name="group" column="group_id" ></many-to-one>
<!--级联(不建议配cascade)
<many-to-one name="group" column="group_id" cascade="save-update"></many-to-one>
-->
</class>
</hibernate-mapping>
Group.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.model">
<class name="Group" table="group1" >
<id name="id" column="group_id" type="java.lang.Integer">
<generator class="native" />
</id>
<property name="name" length="50" type="java.lang.String" />
</class>
</hibernate-mapping>
操作多对一实例:
public class ManyToOneTest extends TestCase{
public void testSave1(){
Session session = null;
Transaction ta = null;
User user = null;
try{
session = HibernateUtil.getSession();
ta = session.beginTransaction();
Group group = new Group();
group.setName("php");
User user1 = new User();
user1.setName("菜10php");
user1.setGroup(group);
User user2 = new User();
user2.setName("Z3php");
user2.setGroup(group);
session.save(group); //若设 cascade="all|save-update" ,则可无此行代码
session.save(user1);
session.save(user2);
ta.commit();
}catch(Exception e){
e.printStackTrace();
ta.rollback();
}finally{
//关闭session, user变为detached离线对象
HibernateUtil.closeSession(session);
}
}
public void testGet1(){
Session session = null;
Transaction ta = null;
User user = null;
try{
session = HibernateUtil.getSession();
ta = session.beginTransaction();
user = (User)session.get(User.class, new Integer(3));
System.out.println("user.name=" + user.getName());
System.out.println("group.name=" + user.getGroup().getName());
ta.commit();
}catch(Exception e){
e.printStackTrace();
ta.rollback();
}finally{
//关闭session, user变为detached离线对象
HibernateUtil.closeSession(session);
}
}
===================================
元素的cascade属性表明操作是否从父对象级联到被关联的对象, 它
的取得可以是以下几种:
none:在保存,删除或修改当前对象时,不对其附属对象(关联对象)进行级联
操作。它是默认值。
save-update:在保存,更新当前对象时,级联保存,更新附属对象(临时对象,
游离对象)。
delete:在删除当前对象时,级联删除附属对象。
all:所有情况下均进行级联操作,即包含save-update和delete操作。