Hibernate多对一单项关联

public class User { 
 private int id; 
 private String name; 
 private Group group; 
  
 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; 
 } 
 public Group getGroup() { 
 return group; 
 } 
 public void setGroup(Group group) { 
 this.group = group; 
 } 
} 

public class Group { 
 private int id; 
 private String name; 
 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; 
 } 

<?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.liang.hibernate"> 
 <class name="User" table="t_user"> 
 <id name="id"> 
  <generator class="native"></generator> 
 </id> 
 <property name="name"></property> 
 <!-- group属性，表达的是本对象与Group的多对一的关系--> 
 <many-to-one name="group" class="Group" column="groupid"></many-to-one> 
 <!-- 解释： 
  多对一关系标签： 
  <many-to-one name=“” class=“” column=“”/> 
  
  1、第1个问号：group是User类的属性，对应于name属性名 
  2、第2个问号：class表达的是本对象(User)与Group的关系 
  3、第3个问号：column是属性名+Id 
  当我们写完注释之后，我们直接拷贝问号的对应关系即可。 
  --> 
 </class> 
</hibernate-mapping> 

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