Cause: java.lang.UnsupportedOperationException] with root cause java.lang.UnsupportedOperationException: null

mapper层接口

   List selectRolePredict(@Param("organId") String organId,@Param("businessId") String businessId);

mybatis.xml sql结构

 <select id="selectRolePredict" resultType="list">
            select  DISTINCT  next_approval_role from business_node_approval_role
            <where>
                organ_id=#{organId} and business_id=#{businessId} and !isnull(next_approval_role)
            </where>
    </select>

解决方法：把resultType=“java.util.List” 改为String

原因:
resultType返回的是集合中的元素类型，而不是集合本身

 <select id="selectRolePredict" resultType="string">
            select  DISTINCT  next_approval_role from business_node_approval_role
            <where>
                organ_id=#{organId} and business_id=#{businessId} and !isnull(next_approval_role)
            </where>
    </select>

修改之后重新启动项目再次测试接口

解决