Hibernate实现many-to-many的映射关系

（1）一个最简单的例子就是学生选课的数据表了



（2）Student.java

public class Course {
private Integer id;
private String name;
private Set<StuCourse> stuCourses;
//get/set方法
}


（3）Student.java
public class Student {
private Integer id;
private String name;
private Set<StuCourse> stuCourses;
<span style="font-family: Arial, Helvetica, sans-serif;">//get/set方法</span>

}
（4）StuCourse.java学生选课表
package com.hsp.domain;

public class StuCourse {
private Integer id;
private Student student;
private Course course;
private Integer grade;
//get/set方法

}


（5）Course.hbm.xml文件
<?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="com.hsp.domain">
<class name="Course">
<id name="id" type="java.lang.Integer">
<generator class="sequence">
<param name="sequence">course_seq</param>
</generator>
</id>
<property name="name" type="java.lang.String">
<column name="name" length="64" />
</property>
<!-- 配置one-to-many 表示一门课程可以对应多个选课记录 -->
<set name="stuCourses">
<key column="course_id" />
<one-to-many class="StuCourse" />
</set>
</class>
</hibernate-mapping>

（6）Student.hbm.xml文件
<?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="com.hsp.domain">
<class name="Student">
<id name="id" type="java.lang.Integer">
<generator class="sequence">
<param name="sequence">stu_seq</param>
</generator>
</id>
<property name="name" type="java.lang.String">
<column name="name" length="64" />
</property>
<!-- 这里我们配置了one-to-many 一个学生可以对应多个选课记录 -->
<set name="stuCourses">
<key column="student_id" /> <!-- 这里的column是外键 -->
<one-to-many class="StuCourse" /> <!-- many所对应的表 -->
</set>
</class>
</hibernate-mapping>

（7）StuCourse.hbm.xml文件
<?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="com.hsp.domain">
<class name="StuCourse">
<id name="id" type="java.lang.Integer">
<generator class="sequence">
<param name="sequence">stucourse_seq</param>
</generator>
</id>
<property name="grade" type="java.lang.Integer">
<column name="grade" length="3" />
</property>
<many-to-one name="course" column="course_id" />
<many-to-one name="student" column="student_id" />
</class>
</hibernate-mapping>

（8）hibernate.cfg.xml文件
<?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="connection.username">root</property>
<property name="connection.url">
jdbc:oracle:thin:@127.0.0.1:1521:OracleDB
</property>
<property name="dialect">
org.hibernate.dialect.Oracle9Dialect
</property>
<property name="connection.password">root</property>
<property name="connection.driver_class">
oracle.jdbc.driver.OracleDriver
</property>
<property name="show_sql">true</property>
<!-- 配置让hibernate自动创建关系模型(表) -->
<property name="hbm2ddl.auto">update</property>
<mapping resource="com/hsp/domain/Course.hbm.xml" />
<mapping resource="com/hsp/domain/StuCourse.hbm.xml" />
<mapping resource="com/hsp/domain/Student.hbm.xml" />

</session-factory>

</hibernate-configuration>