Hibernate学习之路（四）

public class Student {
    private int id;
    private String name;
    private int age;
    private Grade grade;

   set/get....
}

public class Grade {
    private int id;
    private String name;

    set/get....
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
        
<hibernate-mapping>
    <class name="Student">
        <id    name="id">
            <generator class="native"></generator>
        </id>
        
        <property name="name"></property>
        <property name="age"></property>
        
        <!-- 多对一  name 表示属性名  class 指明 属性对应的类 
         column指 数据库表中的列名 -->
        <many-to-one name="grade" class="Grage" column="grade_id" 
        foreign-key="fk_grade" not-null="true"></many-to-one>
    </class>
</hibernate-mapping>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
    <class name="Grade">
        <id name="id">
            <generator class="native"></generator>
        </id>
        
        <property name="name"></property>
    </class>
</hibernate-mapping>

 1 package cn.test;
 2 
 3 import org.hibernate.Session;
 4 import org.hibernate.SessionFactory;
 5 import org.hibernate.cfg.Configuration;
 6 
 7 import cn.pojo.Grade;
 8 import cn.pojo.Student;
 9 import cn.pojo.User;
10 
11 public class TestHibernate {
12     public static void main(String[] args) {
13         //通过Configuration对象创建SessionFactory对象
14         SessionFactory sf = new Configuration().configure().buildSessionFactory();
15         //创建Session对象
16         Session s = sf.openSession();
17         //开启事务
18         s.beginTransaction();
19         
20         //我们只需要关注这里的事务。
21         Grade grade = new Grade();
22         grade.setName("进阶");
23         s.save(grade);
24         Student s1 = new Student();
25         s1.setName("李小龙");
26         s1.setAge(22);
27         s1.setGrade(grade);
28         s.save(s1);
29         //提交事务
30         s.getTransaction().commit();
31         //关闭Session
32         s.close();
33         //关闭SessionFactory
34         sf.close();
35     }
36 }

1 public class Grade{
2     private int id;
3     private String name;      
4     private Set<Student> students = new HashSet<Student>();
5    
6    set/get....  
7 }

<hibernate-mapping package="cn.pojo">
    <class name="Grade">
        <!-- 主键生成策略 -->
        <id name="id" column="id">
            <generator class="native"></generator>
        </id>
        <!-- 实体类的属性 -->
        <property name="name"></property>
        
                <!-- set是 Grade中的集合属性  name属性名称 -->
        <set name="students">
            <!-- key表示外键  column外键列名-->
            <key column="grade_id"  not-null="true"></key>
            <!-- one-to-many 一对多  类Grade 中  students 所表示类型 -->
            <one-to-many class="Student"/>
        </set>
    </class>
</hibernate-mapping>