sql查询结果多对多转为一对多返回前端

企业表 ent_EnterpriseArchives  有id，企业名称 entName

veh_Vehicle 车辆表，有所属企业id  companyId，车辆id，车牌号licPlate

目的是查询企业和车辆的树状结果。如下图，然后返回前端。

执行如下sql得到的结果是：【根据车牌号或者企业名称模糊查询】

SELECT
    ent_EnterpriseArchives.id entId,
    ent_EnterpriseArchives.entName entName,
    veh_Vehicle.id vehId,
    veh_Vehicle.licPlate vehPlate
from ent_EnterpriseArchives
JOIN veh_Vehicle
on  ent_EnterpriseArchives.id = veh_Vehicle.companyId
 
and (
  ent_EnterpriseArchives.entName like '%杭州%' or veh_Vehicle.licPlate like '%杭州%'
)
ORDER BY ent_EnterpriseArchives.id

【上述数据结果为造的假数据】

所以要对这个sql的查询结果进行去重公司名称，返回前端树状结果。下面的代码即为处理过程：

public ResponseList enterpriseVehicleTree(String paramName, HttpSession session) {
        ResponseList response = new ResponseList();
        List<Map<String,List<VehVehicleVO>>> resultList = new ArrayList<Map<String,List<VehVehicleVO>>>();
 
        if(paramName == null) {
            paramName = ConstantUtil.EMPTYSTRING;
        }
        try {
            List<EnterpriseVehicleTreeVO> tempRes = baseMapper.enterpriseVehicleTree(paramName);//上述sql的查询结果
            if(tempRes == null || tempRes.size() < ConstantUtil.INTNUM1) {
                return response;
            }
            Integer tempEntId = null;
            Map<String,List<VehVehicleVO>> tempMap = new HashMap<String, List<VehVehicleVO>>();
            List<VehVehicleVO> tempListStr = new ArrayList<VehVehicleVO>();
            for (int i = 0 ; i < tempRes.size(); i++) {
                EnterpriseVehicleTreeVO enterpriseVehicleTreeVO = tempRes.get(i);
                if(i == ConstantUtil.INTNUM0) {
                    //第一家公司
                    tempEntId = enterpriseVehicleTreeVO.getEntId();
 
                    tempListStr.add( new VehVehicleVO(enterpriseVehicleTreeVO.getVehId(),enterpriseVehicleTreeVO.getVehLicplate()));
 
                    tempMap.put(enterpriseVehicleTreeVO.getEntName(), tempListStr);
                    if((i+1) == tempRes.size()) {
                        resultList.add(tempMap);
                        break;
                    }
                }else {
                    //还是同一家公司
                    if(tempEntId == enterpriseVehicleTreeVO.getEntId()) {
                        tempListStr.add( new VehVehicleVO(enterpriseVehicleTreeVO.getVehId(),enterpriseVehicleTreeVO.getVehLicplate()));
                        tempMap.put(enterpriseVehicleTreeVO.getEntName(), tempListStr);
                        if((i+1) == tempRes.size()) {
                            resultList.add(tempMap);
                        }
                    }else {
                        //新的公司,先处理上一个公司的数据
                        resultList.add(tempMap);
                        tempMap = null;　　　　//注意，这个地方不可以直接调用clear方法去清空，必须重新创建tempMap对象，否则后面的新数据就把之前已经存到list中的上个公司的数据给覆盖掉了
                        tempMap = new HashMap<String, List<VehVehicleVO>>();
                        tempListStr = null;   //原因同上
                        tempListStr = new ArrayList<VehVehicleVO>();
                        tempEntId = enterpriseVehicleTreeVO.getEntId();
                        tempListStr.add( new VehVehicleVO(enterpriseVehicleTreeVO.getVehId(),enterpriseVehicleTreeVO.getVehLicplate()));
                        tempMap.put(enterpriseVehicleTreeVO.getEntName(), tempListStr);
                        if((i+1) == tempRes.size()) {
                            resultList.add(tempMap);
                        }
                    }
                }
            }
            response.setObj(resultList);
        } catch (Exception e) {
            log.info("xxxxxxxxxxxxxxxxxxxxxx异常,==>e.getMessage:" + e.getMessage() + ",==>e.getStackTrace():" + e.getStackTrace()+ ",==>e:" + e);
            response.setSuccess(false).setMsg("xxxxxxxxxxxxxxxxxxxxxxxxx异常");
        }
        return response;
    }

最终效果：

{
  "success": true,
  "msg": "",
  "obj": [
    {
      "杭州科大讯飞": [
        {
          "id": 13,
          "licPlate": "豫QA3586"
        },
        {
          "id": 14,
          "licPlate": "豫QA3585"
        },
        {
          "id": 12,
          "licPlate": "豫QA3587"
        }
      ]
    },
    {
      "杭州网易": [
        {
          "id": 8,
          "licPlate": "浙A36W52"
        }
      ]
    }
  ]
}