hibernate 关联关系

<hibernate-mapping package="com.srts.system.domain">

    <class name="Sys_UserRole" table="srts_sys_userrole">
        <id name="id">
            <generator class="native" />
        </id>
        <many-to-one name="user" class="Sys_User" column="userId" ></many-to-one>
        <many-to-one name="role" class="Sys_Role" column="roleId" ></many-to-one>
    </class>
</hibernate-mapping>