mybatis返回结果映射成ListMapString,Object

mybatis返回结果映射成List<MapString,Object>>
xml:

<select id="getProjectRate"  resultType="java.util.HashMap">
sql......
</select>

mapper：

List<Map<String, Object>> getProjectRate();

service：

@Override
    public List<Map<String, Object>> getProjectRate(){

        return monthlyReportMapper.getProjectRate();
    }

controller:

@RequestMapping(value = "/getProjectRate", method = {RequestMethod.GET})
    public JsonResult getProjectRate(){
        List<Map<String, Object>> list = monthlyReportService.getProjectRate();
        return new JsonResult(StatusCode.OK, list);
    }

返回结果：
mybatis返回结果映射成ListMapString,Object