一 双向多对一生活举例
二 Grade.hbm.xml配置一对多关联关系
xml version="1.0"?>
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="com.imooc.entity.Grade" table="grade">
<id name="gid" column="gid" type="java.lang.Integer">
<generator class="increment">generator>
id>
<property name="gname" type="java.lang.String">
<column name="gname" length="20" not-null="true">column>
property>
<property name="gdesc">
<column name="gdesc">column>
property>
<set name="students" table="student">
<key column="gid">key>
<one-to-many class="com.imooc.entity.Student"/>
set>
class>
hibernate-mapping>
三 Student.hbm.xml配置多对一关联关系
xml version="1.0"?>
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="com.imooc.entity.Student" table="student">
<id name="sid" column="sid" type="java.lang.Integer">
<generator class="increment">generator>
id>
<property name="sname" type="java.lang.String">
<column name="sname" length="20" not-null="true">column>
property>
<property name="sex">
<column name="sex">column>
property>
<many-to-one name="grade" class="com.imooc.entity.Grade" column="gid" >many-to-one>
class>
hibernate-mapping>
四 测试代码
package com.imooc.test;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.imooc.entity.Grade;
import com.imooc.entity.Student;
import com.imooc.util.HibernateUtil;
/*
* 单向多对一（学生--->班级）
*/
public class Test02 {
public static void main(String[] args) {
save();
}
//保存
public static void save(){
Grade g=new Grade("Java一班","Java软件开发一班");
Student stu1=new Student("慕女神", "女");
Student stu2=new Student("小慕慕", "男");
//设置关联关系
g.getStudents().add(stu1);
g.getStudents().add(stu2);
stu1.setGrade(g);
stu2.setGrade(g);
Session session=HibernateUtil.getSession();
Transaction tx=session.beginTransaction();
session.save(g);
session.save(stu1);
session.save(stu2);
tx.commit();
HibernateUtil.closeSession(session);
}
}
五 测试结果
Hibernate: select max(gid) from grade
Hibernate: select max(sid) from student
Hibernate: insert into grade (gname, gdesc, gid) values (?, ?, ?)
Hibernate: insert into student (sname, sex, gid, sid) values (?, ?, ?, ?)
Hibernate: insert into student (sname, sex, gid, sid) values (?, ?, ?, ?)
Hibernate: update student set gid=? where sid=?
Hibernate: update student set gid=? where sid=?
从后台输出来看，多余了两条update语句。
