hibernate多对一的关系，配置问题

hibernate问题:

         如果有两张表分别是userinfo和groupinfo

    userinfo(userId,userName,deptId) groupinfo(groupId,groupName)  ,userinfo里面deptId和groupinfo的groupId是主外键关系。

    那么user.hbm.xml和groupinfo.hbm.xml应该怎么配置。我只要取userinfo就可以取到groupName的值.以下是我的配置，现在可以运行正常

   但就是取不到groupName的值。请问应该怎么配置？？？

 userinfo============================================================

<hibernate-mapping package="org.materialManager.model">
    <class name="UserInfo" table="UserInfo" schema="dbo" catalog="Material">
        <id name="userId" type="integer">
            <column name="userId">
            <generator class="increment">
        </id>

   <many-to-one name="groupinfo" class="GroupInfo" outer-join="true" fetch="select">
            <column name="deptId">
        </many-to-one>

             <property name="userName" type="string">
            <column name="userName" length="50" not-null="true">
        </property>
    </class>

Groupinfo=============================

<hibernate-mapping package="org.materialManager.model">
    <class name="GroupInfo" table="GroupInfo" schema="dbo" catalog="Material">
        <id name="groupId" type="integer">
            <column name="groupId">
            <generator class="increment">
        </id>
        <property name="groupName" type="string">
            <column name="groupName" length="50" not-null="true">
        </property>
        <set name="userInfos">
            <key>
                <column name="deptId">
            </key>
            <one-to-many class="UserInfo">
        </set>
    </class>
</hibernate-mapping>

然后userinfo.getGroupinfo().getGroupname()