hibernate中many-to-one執行個體一

 

可以發現，添加一個教師的同時指定一個學生，這種方式相當糟糕，合理的方式應該是在新增學生的時候指定教師。即在學生類裡指

定教師對象，設定檔裡配置成many-to-one。

單純只使用many-to-one:
在Student類裡加入Teacher teacher屬性。
注釋掉teacher.hbm.xml裡的<set ...></set>內容
在student.hbm.xml裡入many-to-one屬性：

<?xml version="1.0"?><br /><!DOCTYPE hibernate-mapping PUBLIC<br /> "-//Hibernate/Hibernate Mapping DTD 3.0//EN"<br /> "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><br /><hibernate-mapping package="com.sjtu.xw.pojo2"><br /><class name="Student" table="student"><br /><id name="id" column="id"><br /><generator class="native"></generator><br /></id><br /><property name="stuName" column="studentName" length="30" /><br /><many-to-one name="teacher" column="teacherId" class="Teacher"<br />fetch="join" lazy="false" /><br /><!--<br />這裡的column="teacherId"是指明了自身(student表)表裡的teacherId屬性，指向teacher表的外鍵<br />--><br /></class><br /></hibernate-mapping> 

做完上述工作即可進行測試了：

Test2.java

package com.sjtu.xw.test;<br />import java.util.List;<br />import org.hibernate.Session;<br />import org.hibernate.SessionFactory;<br />import org.hibernate.Transaction;<br />import com.sjtu.xw.pojo2.Student;<br />import com.sjtu.xw.pojo2.Teacher;<br />import com.sjtu.xw.util.HibernateUtil;<br />public class Test2 {<br />public static void main(String[] args) {<br />Test2 test = new Test2();<br />// test.addStudent();//通過<br />//test.addTeacher();//通過<br />test.test();<br />}<br />public void addStudent() {<br />Teacher teacher = new Teacher();<br />teacher.setId(1);<br />Student student = new Student();<br />student.setStuName("student8");<br />student.setTeacher(teacher);<br />SessionFactory sf = HibernateUtil.getSessionFactory();<br />Session session = sf.openSession();<br />Transaction tx = session.beginTransaction();<br />session.save(student);<br />tx.commit();<br />session.close();<br />sf.close();<br />}<br />public void addTeacher() {<br />Teacher teacher = new Teacher();<br />teacher.setTeaName("Teacher5");<br />SessionFactory sf = HibernateUtil.getSessionFactory();<br />Session session = sf.openSession();<br />Transaction tx = session.beginTransaction();<br />session.save(teacher);<br />tx.commit();<br />session.close();<br />sf.close();<br />}<br />public void test() {<br />SessionFactory sf = HibernateUtil.getSessionFactory();<br />Session session = sf.openSession();<br />Transaction tx = session.beginTransaction();<br />List list = session.createQuery("from Student s where s.id=1").list();<br />Student s = (Student) list.get(0);//找student的id為1的學生，並擷取老師的資訊。<br />//System.out.println(s);<br />System.out.println(s.getTeacher());<br />System.out.println(s.getTeacher().getTeaName());<br />tx.commit();<br />session.close();<br />sf.close();<br />}<br />}