BlogJava-panda-随笔分类-hibernatehttp://www.blogjava.net/csssoft/category/40664.htmlIT高薪不是梦!!zh-cnMon, 12 Oct 2009 10:19:12 GMTMon, 12 Oct 2009 10:19:12 GMT60Hibernate的多对一关联映射http://www.blogjava.net/csssoft/archive/2009/10/12/297945.htmlIT追求者IT追求者Mon, 12 Oct 2009 09:56:00 GMThttp://www.blogjava.net/csssoft/archive/2009/10/12/297945.htmlhttp://www.blogjava.net/csssoft/comments/297945.htmlhttp://www.blogjava.net/csssoft/archive/2009/10/12/297945.html#Feedback0http://www.blogjava.net/csssoft/comments/commentRss/297945.htmlhttp://www.blogjava.net/csssoft/services/trackbacks/297945.html 1.关联映射的本质：就是将关联关系映射到数据库中，关联关系指对象模型中的一个或多个引用.

2.下面列举多对一的示例：用户和组(多个用户属于一个组)多对一关联映射是最常用的一种关联映射

   *User 类
   package com.lzy
   public class User{

   private int id;
   private String name;

  private Group group;//持有组的引用
   
   public User(){};

   //省略set,get方法
 }

  *Group类
 package com.lzy
 public class Group{
  
   private int id;

   private String name;
   //省略get,set方法
 }

3.对对象进行关系映射，这也是Hibernate中比较难的一点。
  (1)User.hbm.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 package="com.lzy">
         <class name="User" table="t_user">
               <id name="id" column="id">
                     <genarator class="native"/>
              </id>
            <property name="name" column="user_name" not-null="true"/>
            <many-to-one name="group" column="groupid"/>
        </calss>
     </hibernate-mapping>


   (2)Group.hbm.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 package="com.lzy">
         <class name="Group" table="t_group">
               <id name="id" column="id">
                     <genarator class="native"/>
              </id>
            <property name="name" column="group_name" not-null="true"/>
      </class>
   </hibernate-mapping>

4.测试

public class  Test {
   
  public static void main(String args[]){

      SessionFactory  sessionFactory=null;
      Session  session=null;
      Transaction   transaction=null;
      
      sessionFactory = HibernateUtil.getSessionFactory();// 创建一个会话工厂
      session = sessionFactory.openSession();// 创建一个会话实例
      transaction = session.beginTransaction();// 申明一个事务

  User user= new User();
  Group group = new Group();

  user.setName("龙一");

  group.setName("中南大学");
  user.setGroup(group);

  try {

   transaction.begin();
   session.save(user);
   transaction.commit();

  } catch (Exception e) {
   e.printStackTrace();
  }

   }
}



IT追求者 2009-10-12 17:56 发表评论
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