心得7-hibernate级联之多对多转换为多对一的问题剖析
这里与多对多不同的是借用了一个中间类StudentCourse来达到把多对多的问题转换为多对一的问题，下面来举例具体介绍： 先看看三个最重要的xxx.hbm.xml文件内部信息Student.hbm.xml<?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.hbsi.many2manyTOone2many"> <class name="Student" table="s"> <id name="id"> <generator class="native"/> </id> <property name="name" column="name"/> <set name="sc" table="s_c" inverse="true"> <key column="s_id"/> <one-to-many class="StudentCourse"/> </set> </class> </hibernate-mapping> Course.hbm.xml<?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.hbsi.many2manyTOone2many"> <class name="Course" table="c"> <id name="id"> <generator class="native"/> </id> <property name="name" column="name"/> <set name="sc" table="s_c" inverse="true"> <key column="c_id"/> <one-to-many class="StudentCourse"/> </set> </class> </hibernate-mapping> StudentCourse.hbm.xml<?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.hbsi.many2manyTOone2many"> <class name="StudentCourse" table="s_c"> <id name="id"> <generator class="native"/> </id> <property name="score" column="score"/> <many-to-one name="s" column="s_id" cascade="save-update"/><many-to-one name="c" column="c_id" cascade="save-update"/> </class> </hibernate-mapping> 再看看测试文件TestApp.javapackage com.hbsi.many2manyTOone2many; import java.util.Set; import org.hibernate.Session;import org.junit.Test; import com.hbsi.utils.HibernateSessionFactory; public class TestApp { Session session = HibernateSessionFactory.getSession(); @Test public void add(){ session.beginTransaction(); Student stu = new Student(); stu.setName("keven"); Course c1 = new Course(); c1.setName("java"); Course c2 = new Course(); c2.setName("mysql"); StudentCourse sc1 = new StudentCourse(); sc1.setS(stu); sc1.setC(c1); sc1.setScore(99); session.save(sc1); StudentCourse sc2 = new StudentCourse(); sc2.setS(stu); sc2.setC(c2); sc2.setScore(89); session.save(sc2); session.getTransaction().commit(); HibernateSessionFactory.closeSession(); } @Test public void find(){ Student stu = (Student) session.get(Student.class,1); Set<StudentCourse> scs = stu.getSc(); for(StudentCourse sc : scs){ System.out.println(sc.getS().getName()+":"+sc.getC().getName()+"---"+sc.getScore()); } }}