【转】hibernate many-to-one（多对一）及 cascade(级联）
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 />
??????? </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 />
??????? </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。
