hibernate学习笔记10-2

最新推荐文章于 2022-05-28 19:27:56 发布

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最新推荐文章于 2022-05-28 19:27:56 发布

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本文介绍了使用Hibernate实现一对多（多对一）双向关联的方法，包括Java注解和XML映射配置。展示了User和Group两个实体类之间的关联关系。

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一对多（多对一）双向关联

@Entity
@Table(name="t_user")
public class User {
   private int id;
   private String name;
   private Group group;
   @ManyToOne
   public Group getGroup() {
       return group;
   }
   public void setGroup(Group group) {
       this.group = group;
   }
   @Id
   @GeneratedValue
   public int getId() {
       return id;
   }
   public void setId(int id) {
       this.id = id;
   }
   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }
}

或xml

<hibernate-mapping>
   <class name="com.bjsxt.hibernate.User" table="t_user">
       <id name="id">
           <generator class="native"></generator>
       </id>

       <property name="name"></property>
       <many-to-one name="group" column="groupId"></many-to-one>
    </class>

</hibernate-mapping>

@Entity
@Table(name="t_group")
public class Group {
   private int id;
   private String name;
   private Set<User> users = new HashSet<User>();
   @Id
   @GeneratedValue
   public int getId() {
       return id;
   }
   public void setId(int id) {
       this.id = id;
   }
   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }
   @OneToMany(mappedBy="group")

   public Set<User> getUsers() {
       return users;
   }
   public void setUsers(Set<User> users) {
       this.users = users;
   }
}

或xml

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

       <property name="name"></property>
       <set name="users">
           <key column="groupId"></key>
           <one-to-many class="com.bjsxt.hibernate.User"/>
       </set>
    </class>

</hibernate-mapping>