mybatis 3张表查询，为什么查询出了值但获取时却为空

Question

在xml中配置关系resutmap如下：

<mapper namespace="com.hwsensor.framework.dao.IRolePermissionDao">
<!-- 联合permission，role，per-role的查询 --> 
<resultMap id="detailedPerRoleResultMap" type="RolePerPO">
    <id property="id" column="ID" />
    <result property="roleId" column="ROLE_ID" />
    <result property="permId" column="PERM_ID" />
    <result property="action" column="ACTION" />
    <result property="available" column="AVAILABLE" />
    <association property="permId" column="perm_id" javaType="PermissionPO">
  <id property="id" column="ID" />
  <result property="parentId" column="PARENTID" />
  <result property="name" column="NAME" />
  <result property="url" column="URL" />
  <result property="image" column="IMAGE" />
  <result property="available" column="AVAILABLE" />
  <result property="admin" column="ADMIN" />
  <result property="orderNum" column="ORDERNUM" />
  <result property="description" column="DESCRIPTION" />    
    </association>
    <collection property="roleId" ofType="RolePO">
   <id property="id" column="ID" />
  <result property="parentId" column="PARENTID" />
  <result property="name" column="NAME" />
  <result property="description" column="DESCRIPTION" />  
    </collection>
</resultMap>

<!-- 根据permission的id查询三张表 -->
 <select id="retrievePerRoleDetails" parameterType="java.lang.String" resultMap="detailedPerRoleResultMap">
           SELECT
                RP.ID            RPID,
                                         RP.ROLE_ID       RPROLEID,
                                         RP.PERM_ID       RPPERID,
                                         RP.ACTION        RPACTION,
                                         RP.AVAILABLE     RPAVAILABLE,
                                         PER.ID           PERID,
                                         PER.PARENTID     PERPARENTID,
                                         PER.NAME         PERNAME,
                                         PER.URL          PERURL,
                                         PER.IMAGE        PERIMAGE,
                                         PER.AVAILABLE    PERAVAILABLE,
                                         PER.ADMIN        PERADMIN,
                                         PER.ORDERNUM     PERORDERNUM,
                                         PER.DESCRIPTION  PERDESCRIPTION,
                                         ROLE.ID          ROLEID,
                                         ROLE.NAME        ROLENAME,
                                         ROLE.DESCRIPTION ROLEDESCRIPTION
                                      FROM SYS_ROLE_PERM  RP,
                                         SYS_PERMISSION PER,
                                         SYS_ROLE       ROLE
                                         WHERE RP.ROLE_ID = ROLE.ID
                                           AND RP.PERM_ID = PER.ID
                                            AND RP.PERM_ID =  #{permId}
</mapper>

在action中获得的对象的List<RolePermPO>为空，但是它的长度存在，在控制端也打印出了查询出的数据，就是获取的List<RolePermPO>为空？为什么啊？

Answer 1

不会吧！

Answer 2

是的啊 直接报错了，我用的另外一种方法实现的

Answer 3

先谢谢回答了啊，试过之后不行啊 这样的话 直接报错了