mybatis返回map结果集@MapKey使用的场景分析

@MapKey("id")
Map<Long, UserInfo> getUserInfoMap();

@MapKey("id")
Map<Long, Map<String,Object>> getUserValueMap();

@MapKey("name")
Map<name, UserInfo> getUserInfoMap();
  ..............返回一条记录...............
Map<String, Object> getUserInfoMapById();

<select id="getInfoById" resultType="java.util.Map">
    select
    ext.id as id,
    info.produce_area as area,
    ext.attribute_value as companyName
    from product_info info
    left join product_ext ext on info.id=ext.id
    where info.id=#{id} and ext.attribute_name=#{name}
</select>

@MapKey("id")
Map<Long,Map<String,String>> getInfoById(@Param("id") Long id, @Param("name") String name);

// 查询，返回结果:{1={area:上海,companyName=西西公司}}
// 如果是多条记录，返回结果如:{1={area:上海,companyName:西西公司},2={area:南京,compantyName:猴猴公司}}
Map<Long, Map<String, String>> map = productDao.getInfoById(id, "公司名称"); 
if(map==null || map.isEmpty() || !map.containsKey(id)){
    return null;
}
// 获取结果
String area = produceInfoMap.get(id).get("area");
String companyName = produceInfoMap.get(productTracInfoId).get("companyName");