Hibernate集合映射之Bag

create table teamBag (id varchar( 32 ),teamname varchar( 32 ));
create table studentBag(id varchar( 32 ),cardid varchar( 32 ),name varchar( 32 ),age  int ,description varchar( 32 ), team_id varchar( 32 ),cid varchar( 32 ));

package  Collection.Bag;

public   class  Student  ... {
   private  String id;
   private  String name;
   private  String description;
   private   int  age;
   private  String cardid;
   private  Team team;
public  String getId()  ... {
     return  id;
}
public   void  setId(String id)  ... {
     this .id  =  id;
}
public  String getName()  ... {
     return  name;
}
public   void  setName(String name)  ... {
     this .name  =  name;
}
public  String getDescription()  ... {
     return  description;
}
public   void  setDescription(String description)  ... {
     this .description  =  description;
}
public   int  getAge()  ... {
     return  age;
}
public   void  setAge( int  age)  ... {
     this .age  =  age;
}
public  String getCardid()  ... {
     return  cardid;
}
public   void  setCardid(String cardid)  ... {
     this .cardid  =  cardid;
}
public  Team getTeam()  ... {
     return  team;
}
public   void  setTeam(Team team)  ... {
     this .team  =  team;
}
}



package  Collection.Bag;

import  java.util.ArrayList;
import  java.util.List;
import  java.util.Map;

public   class  Team  ... {
    private  String id;
    private  String teamname;
    private  List students = new  ArrayList();
public  String getId()  ... {
     return  id;
}
public   void  setId(String id)  ... {
     this .id  =  id;
}
public  String getTeamname()  ... {
     return  teamname;
}
public   void  setTeamname(String teamname)  ... {
     this .teamname  =  teamname;
}
public  List getStudents()  ... {
     return  students;
}
public   void  setStudents(List students)  ... {
     this .students  =  students;
}

}

<? 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 ="Collection.Bag.Student"  table ="studentBag"   >
     < id  name ="id"  unsaved-value ="null" >
       < generator  class ="uuid.hex" ></ generator >
     </ id >
     < property  name ="cardid"  type ="string"  column ="cardid" ></ property >
     < property  name ="name"  type ="string"  column ="name" ></ property >
     < property  name ="age"  type ="int"  column ="age" ></ property >
     < property  name ="description"  type ="string"  column ="description" ></ property >  
     < many-to-one  name ="team"  
                 column ="team_id"
                 class ="Collection.Bag.Team"  
                 cascade ="none"  
                 fetch ="join" >
     </ many-to-one >
</ class >

</ hibernate-mapping >

<? 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 ="Collection.Bag.Team"  table ="teamBag"   >
     < id  name ="id"  unsaved-value ="null" >
       < generator  class ="uuid.hex" ></ generator >
     </ id >
     < property  name ="teamname"  type ="string"  column ="teamname" ></ property >
        < bag  name ="students"  table ="studentBag"  cascade ="all,delete-orphan"   >

       < key  column ="team_id" ></ key >
       < one-to-many  class ="Collection.Bag.Student" />
     </ bag >
</ class >

</ hibernate-mapping >

<? 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