Hibernate关联学习之---多对多关联

有两个实Student和Course,他们之间的关系是多对多，在数据库上，为了满足3NF,会建立一个中间表Stu_Course来维护Student和Course之间的关系，在Hibernate中，则使用双向多对多来体现这种结构

数据库脚本

 

create table stu(id varchar(32) primary key,name varchar(32),cardid varchar(32),age int);
create table course(id varchar(32) primary key,name varchar(32));
create table stu_course(stu_id varchar(32),course_id varchar(32));



insert into stu values("1","tom","200701",11);
insert into stu values("2","tomclus","200702",11);
insert into stu values("3","spark","200703",11);
insert into stu values("4","jerry","200704",11);

insert into course values("1","history");
insert into course values("2","computer");
insert into course values("3","music");
insert into course values("4","encomic");
insert into course values("5","politics");

insert into stu_course values("2","1");
insert into stu_course values("2","2");
insert into stu_course values("2","3");
insert into stu_course values("1","3");
insert into stu_course values("1","4");
insert into stu_course values("3","2");
insert into stu_course values("3","3");

 POJO:

 

package Relation.ManytoMany;

import java.util.Set;


public class Stu ...{
  private String id;
  private String cardid;
  private String name;
  private int age;
  private Set course;
public Set getCourse() ...{
    return course;
}
public void setCourse(Set course) ...{
    this.course = course;
}
public String getId() ...{
    return id;
}
public void setId(String id) ...{
    this.id = id;
}
public String getCardid() ...{
    return cardid;
}
public void setCardid(String cardid) ...{
    this.cardid = cardid;
}
public String getName() ...{
    return name;
}
public void setName(String name) ...{
    this.name = name;
}
public int getAge() ...{
    return age;
}
public void setAge(int age) ...{
    this.age = age;
}


}



package Relation.ManytoMany;


import java.util.HashSet;
import java.util.Set;

public class Course ...{
   private String id;
   private Set students;
   private String name;
public String getId() ...{
    return id;
}
public void setId(String id) ...{
    this.id = id;
}

public Set getStudents() ...{
    return students;
}
public void setStudents(Set students) ...{
    this.students = students;
}
public String getName() ...{
    return name;
}
public void setName(String name) ...{
    this.name = name;
}



}

 

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="connection.username">root</property>
    <property name="connection.url">
        jdbc:mysql://localhost:3306/schoolproject?characterEncoding=gb2312&amp;useUnicode=true
    </property>
    <property name="dialect">
        org.hibernate.dialect.MySQLDialect
    </property>
    <property name="myeclipse.connection.profile">mysql</property>
    <property name="connection.password">1234</property>
    <property name="connection.driver_class">
        com.mysql.jdbc.Driver
    </property>
    <property name="hibernate.dialect">
        org.hibernate.dialect.MySQLDialect
    </property>
    <property name="hibernate.show_sql">true</property>
    <property name="current_session_context_class">thread</property>
    <property name="jdbc.batch_size">15</property>
    <mapping resource="Relation/ManytoMany/Course.hbm.xml" />
    <mapping resource="Relation/ManytoMany/Stu.hbm.xml" />



</session-factory>

</hibernate-configuration>

 

Stu.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">
<!-- 
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping>
<class name="Relation.ManytoMany.Stu" table="stu">
  <id name="id" unsaved-value="null">
    <generator class="uuid.hex"></generator>
  </id>
  <property name="cardid" type="string"/>
  <property name="name" type="string"/>
  <property name="age" type="int"/>
&nb