hibernate学习之m:m投射

hibernate学习之m:m映射
1、包结构:


2、源代码：
Course.java

package domain;import java.util.HashSet;import java.util.Set;public class Course {private String id;private String cid;private String course;private Set<Student> students=new HashSet<Student>();public Course() {}public Course(String cid, String course) {this.cid = cid;this.course = course;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getCid() {return cid;}public void setCid(String cid) {this.cid = cid;}public String getCourse() {return course;}public void setCourse(String course) {this.course = course;}public Set<Student> getStudents() {return students;}public void setStudents(Set<Student> students) {this.students = students;}}

Student.java:

package domain;import java.util.HashSet;import java.util.Set;public class Student {private String id;private String sid;private String name;private Set<Course> courses=new HashSet<Course>();public Student(){};public Student(String sid,String name){this.sid=sid;this.name=name;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getSid() {return sid;}public void setSid(String sid) {this.sid = sid;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Set<Course> getCourses() {return courses;}public void setCourses(Set<Course> courses) {this.courses = courses;}}

HbnUtil.java:

package util;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;public class HbnUtil {private static SessionFactory sessionFactory;private HbnUtil(){}public static synchronized SessionFactory getSessionFactory(){if(sessionFactory==null){sessionFactory=new Configuration().configure().buildSessionFactory();}return sessionFactory;}}

hibernate.cfg.xml:

<?xml version='1.0' encoding='UTF-8'?><!DOCTYPE hibernate-configuration PUBLIC          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><!-- Generated by MyEclipse Hibernate Tools.                   --><hibernate-configuration>    <session-factory>        <property name="dialect">org.hibernate.dialect.Oracle9Dialect</property>        <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:myorcl</property>        <property name="connection.username">myorcl</property>        <property name="connection.password">embed</property>        <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>        <property name="myeclipse.connection.profile">myorcl</property>    <!--<property name="hibernate.connection.release_mode">AFTER_TRANSACTION</property>    -->    <property name="show_sql">true</property>    <mapping resource="domain/Student.hbm.xml"/>    <mapping resource="domain/Course.hbm.xml"/>    </session-factory></hibernate-configuration>

Course.hbm.xml

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" ><hibernate-mapping package="domain"><class name="Course" table="COURSE"><id name="id" column="id"><generator column="cid"></property><property name="course" column="course"></property><set name="students" table="SC" inverse="true"><key column="CFK"></key><many-to-many column="SFK"></many-to-many></set></class></hibernate-mapping>

Student.hbm.xml:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" ><hibernate-mapping package="domain"><class name="Student" table="STUDENT"><id name="id" column="ID"><generator column="SID"></property><property name="name" column="NAME"></property><set name="courses" table="SC" cascade="all"><key column="SFK"></key><many-to-many column="CFK"></many-to-many></set></class></hibernate-mapping>

Test.java:

package test;import org.hibernate.Session;import org.hibernate.SessionFactory;import util.HbnUtil;import domain.Course;import domain.Student;public class Test {public static void main(String[] args){SessionFactory sf=HbnUtil.getSessionFactory();Session session=sf.openSession();session.beginTransaction();Student s1=new Student("sid4","li");Course c1=new Course("cid4","C++");Student s2=new Student("sid5","li");Course c2=new Course("cid5","C++");s1.getCourses().add(c1);s1.getCourses().add(c2);c2.getStudents().add(s2);//session.save(s1);//session.save(c1);//session.save(c2);//session.save(s2);Object obj=session.get(Student.class, "4028e4282e091aa1012e091aa5420001");session.delete(obj);session.flush();session.getTransaction().commit();session.close();sf.close();}}

以上代码使用中间表SC实现了多对多关系映射，但我还有一个疑问：就是如果中间表SC还想加入一个score（学生分数）字段，该如何处理呢？网上有人说将多对多映射拆成两个一对多映射。大家都是这么做的么？

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