mybatis map list

作者: 少年未老丶心已荒凉
来源: 51数据库
2020-10-01

Mapper里面返回List，就是说Mapper里面的方法声明是
public List
dao、service层也作相应修改，改为返回List<Map<String,Object>>
<mapper namespace="com.brkc.epolice.mysql.dao.OnlineStatMapper" >
<select id="selectOnlineRateCurrent" resultType="java.util.HashMap" >
SELECT count(*) value, c. NAME label, ifnull(b.device_status, 0) device_status
FROM td01_device a
LEFT OUTER JOIN td06_device_status b ON a.id = b.device_id
LEFT OUTER JOIN td05_dd_device_status c ON c.ID = ifnull(b.device_status, 0)
GROUP BY ifnull(b.device_status, 0), c. NAME
ORDER BY device_status
</select>

</mapper>
public interface OnlineStatMapper {
public List<Map<String, Object>> selectOnlineRateCurrent();
}

　　好像是因为你用的是select *，结果有多行返回结果，但是你的mapper里面返回是的object。
要么返回list<>>，要么用select top 1之类的

推荐阅读