Hibernate 多对多例

SQL(MY SQL):
create table tgroup (
  group_id int not null auto_increment,
  name varchar(16) not null default '',
  primary key  (group_id)
) type=innodb;

create table trole (
  role_id int not null auto_increment,
  name varchar(16) not null default '',
  primary key  (role_id)
) type=innodb;

create table tgroup_role (
  group_id int not null,
  role_id int not null,
  primary key(group_id, role_id),
  index (group_id),
  foreign key (group_id) references tgroup(group_id),
  index (role_id),
  foreign key (role_id) references trole(role_id)
) type=innodb;

Group 类：
package ivan.hibernate.many2many;
public class Group {
   private int id;
   private String name;
   private Set roles = new HashSet();
   ...
}

Group.hbm.xml：
<hibernate-mapping>
    <class name="ivan.hibernate.many2many.Group" table="tgroup">
        <id name="id" column="group_id" unsaved-value="0">
            <generator class="increment"/>
        </id>
        <property name="name" type="string"/>     
        <set name="roles"
             table="tgroup_role"
             cascade="save-update">           
             <key column="group_id"/>
             <many-to-many class="ivan.hibernate.many2many.Role"
                           column="role_id"/>
       </set>
    </class>
</hibernate-mapping>

Role 类：
package ivan.hibernate.many2many;
public class Role {
   private int id;
   private String name;
   private Set groups = new HashSet();
   ...
}

Role.hbm.xml：
<hibernate-mapping>
    <class name="ivan.hibernate.many2many.Role" table="trole">
        <id name="id" column="role_id" unsaved-value="0">
            <generator class="increment"/>
        </id>
        <property name="name" type="string"/>     
        <set name="groups"
             table="tgroup_role"
             inverse="true"
             cascade="save-update">           
             <key column="role_id"/>
             <many-to-many class="ivan.hibernate.many2many.Group"
                           column="group_id"/>
  </set>
    </class>
</hibernate-mapping>

hibernate.cfg.xml 同前面的例子差不多。

public class Test {

public static void main(String[] args) throws HibernateException {
   
  Role role1 = new Role();
  role1.setName("Role1");
  Role role2 = new Role();
  role2.setName("Role2");
  Role role3 = new Role();
  role3.setName("Role3");
  Group group1 = new Group();
  group1.setName("group1");
  Group group2 = new Group();
  group2.setName("group2");
  Group group3 = new Group();
  group3.setName("group3");
  group1.getRoles().add(role1);
  group1.getRoles().add(role2);
  group2.getRoles().add(role2);
  group2.getRoles().add(role3);
  group3.getRoles().add(role1);
  group3.getRoles().add(role3);
  role1.getGroups().add(group1);
  role1.getGroups().add(group3);
  role2.getGroups().add(group1);
  role2.getGroups().add(group2);
  role3.getGroups().add(group2);
  role3.getGroups().add(group3);

  SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
  Session session = sessionFactory.openSession();
  Transaction tx= session.beginTransaction();
  session.save(role1);
  session.save(role2);
  session.save(role3);
  session.save(group1);
  session.save(group2);
  session.save(group3);
  tx.commit();
  session.close();
  sessionFactory.close();
}
}