Hibernate中的manytomany映射实例一

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转自：http://blog.csdn.net/woshisap/article/details/6448774

2：User的配置文件为：

<hibernate-mapping >
<class name="com.bjsxt.hibernate.User" table="t_user">
     <id name="id">
         <generator class="native"/>
     </id>
     <property name="name"/>
     <set name="roles" table="t_user_role">
         <key column="userid"/>
         <many-to-many class="com.bjsxt.hibernate.Role" column="roleid"/>
     </set>
</class>
</hibernate-mapping>

Role的配置文件为：

<hibernate-mapping >
<class name="com.bjsxt.hibernate.Role" table="t_role">
     <id name="id">
         <generator class="native"/>
     </id>
     <property name="name"/>
     <set name="users" table="t_user_role" order-by="userid">
          <key column="roleid"/>
          <many-to-many class="com.bjsxt.hibernate.User" column="userid"/>
     </set>
</class>
</hibernate-mapping>

3：测试程序为：

public void testSave1(){   //首先保存Role，再保存User
  Session session = null;
  try{
   session = HibernateUtils.getSession();
   session.beginTransaction();

   Role r1 = new Role();
   r1.setName("数据录入人员");
   session.save(r1);

   Role r2 = new Role();
   r2.setName("商务主管");
   session.save(r2);

   Role r3 = new Role();
   r3.setName("大区经理");
   session.save(r3);

   User u1 = new User();
   u1.setName("10");

   Set u1Roles = new HashSet();
   u1Roles.add(r1);
   u1Roles.add(r2);
   u1.setRoles(u1Roles);

   User u2 = new User();
   u2.setName("aaa");
   Set u2Roles = new HashSet();
   u2Roles.add(r2);
   u2Roles.add(r3);
   u2.setRoles(u2Roles);

   User u3 = new User();
   u3.setName("kjj");
   Set u3Roles = new HashSet();
   u3Roles.add(r1);
   u3Roles.add(r2);
   u3Roles.add(r3);
   u3.setRoles(u3Roles);

   session.save(u1);
   session.save(u2);
   session.save(u3);

   session.getTransaction().commit();

  }catch(Exception e){
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally{
   HibernateUtils.closeSession(session);
  }
}

//首先加载User，根据User来加载Role

public void testLoad1(){
  Session session = null;
  try{
   session = HibernateUtils.getSession();
   session.beginTransaction();

   User user = (User)session.load(User.class,1);
   System.out.println(user.getName());

   for(Iterator iter = user.getRoles().iterator();iter.hasNext();){
    Role role = (Role)iter.next();
    System.out.println("role.name"+role.getName());
   }
   session.getTransaction().commit();
  }catch(Exception e){
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally{
   HibernateUtils.closeSession(session);
  }
}

//首先加载Role，再根据Role来加载User
public void testLoad2(){
  Session session = null;
  try{
   session = HibernateUtils.getSession();
   session.beginTransaction();

   Role role = (Role) session.load(Role.class,1);
   System.out.println("role.name"+role.getName());
   for(Iterator iter = role.getUsers().iterator();iter.hasNext(); ){
    User student = (User)iter.next();
    System.out.println("student.name:"+student.getName());
   }
   session.getTransaction().commit();
  }catch(Exception e){
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally{
   HibernateUtils.closeSession(session);
  }
}
}

总结：

hibernate多对多关联映射(双向User<----->Role)

具体映射方式：
   <set name="roles" table="t_user_role">
            <key column="userid"/>
            <many-to-many class="com.bjsxt.hibernate.Role" column="roleid"/>
   </set>

table属性值必须和单向关联中的table属性值一致
<key>中column属性值要和单向关联中<many-to-many>标签中的column属性值一致
<many-to-many>中的column属性值要与单向关联中<key>标签的column属性值一致

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