hibernate 一对多的映射-优快云博客

本文介绍了Hibernate框架下一对多关系的实现方式，通过User和Group类的实例演示了如何使用<many-to-one>标签建立关系，并展示了如何利用cascade属性进行级联操作。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

今天学了HIBERNATE的一对多的关系，嗯它真的太好了，很方便确实

many2one

就是这样一种思想:

新建一个User类和 Group 类如下：

                private int id;

                private String username;

                 private Group group;

private int id;

private String name;

Group.hbm.xml

hibernate-mapping>
<class name="hibernate.Group" table="t_group">
<id name="id">
<generator class="native"/>
</id>
<property name="name"/>
</class>

</hibernate-mapping>

User.hbm.xml

hibernate-mapping>
<class name="hibernate.User" table="t_user">
<id name="id">
<generator class="native"/>
</id>
<property name="username"/>
<many-to-one name="group" column="groupid" cascade="all"/>
</class>

</hibernate-mapping>

testSave

public void testSave1() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();

   Group group = new Group();
   group.setName("试点班");
   group.setId(1);

   User user1 = new User();
   user1.setUsername("***1");
   user1.setGroup(group);
   User user2 = new User();
   user2.setUsername("***2");
   user2.setGroup(group);

   session.save(user1);
   session.save(user2);
   session.getTransaction().commit();
  }catch(Exception e) {
   session.getTransaction().rollback();
   e.printStackTrace();
  }finally {
   HibernateUtils.closeSession(session);
  }

//直接查询

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

   User user = (User)session.load(User.class, 3);
   System.out.println("user name= "+ user.getUsername());
   System.out.println("group name = "+ user.getGroup().getName());
   session.getTransaction().commit();
  }catch(Exception e) {
   session.getTransaction().rollback();
   e.printStackTrace();
  }finally {
   HibernateUtils.closeSession(session);
  }
}