hibernate中many-to-one实例一

可以发现，添加一个教师的同时指定一个学生，这种方式相当糟糕，合理的方式应该是在添加学生的时候指定教师。即在学生类里指

定教师对象，配置文件里配置成many-to-one。

单纯只使用many-to-one:
在Student类里加入Teacher teacher属性。
注释掉teacher.hbm.xml里的<set ...></set>内容
在student.hbm.xml里入many-to-one属性：

<?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.sjtu.xw.pojo2">
<class name="Student" table="student">
<id name="id" column="id">
<generator class="native"></generator>
</id>
<property name="stuName" column="studentName" length="30" />
<many-to-one name="teacher" column="teacherId" class="Teacher"
fetch="join" lazy="false" />
<!--
这里的column="teacherId"是指明了自身(student表)表里的teacherId属性，指向teacher表的外键
-->
</class>
</hibernate-mapping>

做完上述工作即可进行测试了：

Test2.java

package com.sjtu.xw.test;
import java.util.List;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import com.sjtu.xw.pojo2.Student;
import com.sjtu.xw.pojo2.Teacher;
import com.sjtu.xw.util.HibernateUtil;
public class Test2 {
public static void main(String[] args) {
Test2 test = new Test2();
// test.addStudent();//通过
//test.addTeacher();//通过
test.test();
}
public void addStudent() {
Teacher teacher = new Teacher();
teacher.setId(1);
Student student = new Student();
student.setStuName("student8");
student.setTeacher(teacher);
SessionFactory sf = HibernateUtil.getSessionFactory();
Session session = sf.openSession();
Transaction tx = session.beginTransaction();
session.save(student);
tx.commit();
session.close();
sf.close();
}
public void addTeacher() {
Teacher teacher = new Teacher();
teacher.setTeaName("Teacher5");
SessionFactory sf = HibernateUtil.getSessionFactory();
Session session = sf.openSession();
Transaction tx = session.beginTransaction();
session.save(teacher);
tx.commit();
session.close();
sf.close();
}
public void test() {
SessionFactory sf = HibernateUtil.getSessionFactory();
Session session = sf.openSession();
Transaction tx = session.beginTransaction();
List list = session.createQuery("from Student s where s.id=1").list();
Student s = (Student) list.get(0);//找student的id为1的学生，并获取老师的信息。
//	System.out.println(s);
System.out.println(s.getTeacher());
System.out.println(s.getTeacher().getTeaName());
tx.commit();
session.close();
sf.close();
}
}