hibernate多对多

hibernate 多对多处理设置
    例如角色与权限：
角色中：
private Set privileges= new HashSet();
权限中：
private Set<Role> roles = new HashSet<Role>();

    <class name="entity.Role" table="ROLE" dynamic-update="true">
        <id name="roleId" type="java.lang.Integer">
            <column name="roleID" />
            <generator class="identity"></generator>
        </id>
        <property name="roleName" type="java.lang.String">
            <column name="roleName" length="50" />
        </property>
        <property name="mender" type="java.lang.Integer">
            <column name="mender" />
        </property>
        <property name="modifyTime" type="java.sql.Timestamp">
            <column name="modifyTime" length="50" />
        </property>
        <set name="privileges"  cascade="all"  table="ROLE_PRIVILEGE" lazy="true">
            <key column="roleID" />
            <many-to-many class="entity.Privilege" column="pvID" order-by="sequence"/>
        </set>
    </class>



    <class name="entity.Privilege" table="PRIVILEGE">
        <id name="pvId" type="java.lang.Integer">
            <column name="pvID" />
            <generator class="identity"></generator>
        </id>
        <property name="parentId" type="java.lang.Integer">
            <column name="parentID" />
        </property>
        <property name="pvName" type="java.lang.String">
            <column name="pvName" length="50" />
        </property>
        <property name="level" type="java.lang.Short">
            <column name="level" />
        </property>
        <property name="url" type="java.lang.String">
            <column name="url" length="50" />
        </property>
        <property name="isView" type="java.lang.Short">
            <column name="isView" />
        </property>
         <property name="modifyTime" type="java.sql.Timestamp">
            <column name="modifyTime" length="50" />
        </property>
        <set name="roles" table="ROLE_PRIVILEGE" lazy="true"  cascade="none">
        <key column="pvID" />
        <many-to-many class="entity.Role" column="roleID" />
        </set>
    </class>
   
    修改角色的时候 1 根据id去查询角色实体
   2 将需要更新的字段更新到查询出来的角色实体中

    修改角色的权限  1删除当前角色的权限
    2 添加当前角色权限
    实例：
public  void updatePvRole(Integer[] pvIds , Integer roleId   ){
if( pvIds==null || pvIds.length==0){
return ;
}
Role role = roleDao.getRole(roleId);
Set setOld = role.getPrivileges();
Iterator it = setOld.iterator();
while(it.hasNext()){
it.next();
it.remove();
}

for( Integer pvId :pvIds ){
Privilege privilege =  privilegeDao.getPrivilege( pvId );
setOld.add( privilege );
}
roleDao.updateRole( role );
}