Hibernate多对多双向关联(xml配置)

Role.java 
package  com.many2many.bean;

import  java.util.Set;

public   class  Role {
    
     private   int  id;
     private  String name;
     private  Set < User >  users;
     public   int  getId() {
         return  id;
    }
     public   void  setId( int  id) {
         this .id  =  id;
    }
     public  String getName() {
         return  name;
    }
     public   void  setName(String name) {
         this .name  =  name;
    }
     public  Set < User >  getUsers() {
         return  users;
    }
     public   void  setUsers(Set < User >  users) {
         this .users  =  users;
    }
    
}
User.java 
package  com.many2many.bean;

import  java.util.Set;

public   class  User {
    
     private   int  id;
     private  String name;
     private  Set < Role >  roles;
     public   int  getId() {
         return  id;
    }
     public   void  setId( int  id) {
         this .id  =  id;
    }
     public  String getName() {
         return  name;
    }
     public   void  setName(String name) {
         this .name  =  name;
    }
     public  Set < Role >  getRoles() {
         return  roles;
    }
     public   void  setRoles(Set < Role >  roles) {
         this .roles  =  roles;
    }
    
}
映射文件 
Role.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 ="com.many2many.bean" > 
         < class  name ="Role"  table ="roles"  catalog ="Hibernate_Many2Many" > 
             < id  name ="id"  column ="id" > 
                 < generator  class ="native" /> 
             </ id > 
             < property  name ="name"  column ="name" /> 
             < set  name ="users"  table ="user_role"  cascade ="all" > 
                 < key > 
                     < column  name ="role_id" /> 
                 </ key > 
                 < many-to-many  column ="user_id"  class ="User" /> 
             </ set > 
         </ class > 
     </ hibernate-mapping >

User.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 ="com.many2many.bean" > 
         < class  name ="User"  table ="users"  catalog ="Hibernate_Many2Many" > 
             < id  name ="id"  column ="id" > 
                 < generator  class ="native" /> 
             </ id > 
             < property  name ="name"  column ="name" /> 
             < set  name ="roles"  table ="user_role"  cascade ="all" > 
                 < key > 
                     < column  name ="user_id" /> 
                 </ key > 
                 < many-to-many  column ="role_id"  class ="Role" /> 
             </ set > 
         </ class > 
     </ hibernate-mapping >

导出的sql 
create   table  Hibernate_Many2Many.roles (
        id  integer   not   null  auto_increment,
        name  varchar ( 255 ),
         primary   key  (id)
    )

     create   table  Hibernate_Many2Many.users (
        id  integer   not   null  auto_increment,
        name  varchar ( 255 ),
         primary   key  (id)
    )

     create   table  user_role (
        role_id  integer   not   null ,
         user_id   integer   not   null ,
         primary   key  ( user_id , role_id)
    )

     alter   table  user_role 
         add   index  FK143BF46ADA6B394F (role_id), 
         add   constraint  FK143BF46ADA6B394F 
         foreign   key  (role_id) 
         references  Hibernate_Many2Many.roles (id)

     alter   table  user_role 
         add   index  FK143BF46A7F95FD2F ( user_id ), 
         add   constraint  FK143BF46A7F95FD2F 
         foreign   key  ( user_id ) 
         references  Hibernate_Many2Many.users (id)

测试代码 
@Test
     public   void  insert(){
        Session session = HibernateSessionFactory.getSession();
        Transaction transaction = session.beginTransaction();
         try  {
            transaction.begin();
            User user = new  User();
            user.setName( " 张三 " );
            
            Role role = new  Role();
            role.setName( " 管理员 " );
            Set < Role >  roles = new  HashSet < Role > ();
            roles.add(role);
            user.setRoles(roles);
            
            session.persist(user);
            
            transaction.commit();
        }  catch  (HibernateException e) {
            e.printStackTrace();
            transaction.rollback();
        }
    }
    
    
    @Test
     public   void  select(){
        Session session = HibernateSessionFactory.getSession();
        User user = (User) session.get(User. class ,  1 );
        System.out.println(user.getName());
        Set < Role >  roles = user.getRoles();
         for  (Iterator < Role >  iterator  =  roles.iterator(); iterator.hasNext();) {
            Role role  =  (Role) iterator.next();
            System.out.println(role.getName());
        }
    }