hibernate中many-to-one实例一

最新推荐文章于 2018-10-28 22:12:00 发布

xw13106209

最新推荐文章于 2018-10-28 22:12:00 发布

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分类专栏： JAVA 文章标签： hibernate session class generator list string

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本文介绍如何在Hibernate中实现学生与教师之间的多对一关系映射，通过配置XML文件和Java代码示例，详细解释了具体实现过程。

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" />  </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(); } }