如下，我們要返回下面的資料格式

 {
      "value": "3",
      "label": "安徽省",
      "children": [
        {
          "value": "安慶市",
          "label": "36",
          "children1s": [
            {
              "label": "398",
              "value": "迎江區"
            },
            {
              "label": "399",
              "value": "大觀區"
            },
            {
              "label": "400",
              "value": "宜秀區"
            },
            {
              "label": "401",
              "value": "桐城市"
            },
            {
              "label": "402",
              "value": "懷寧縣"
            },
            {
              "label": "403",
              "value": "樅陽縣"
            },
            {
 

那麼可以通過構造輔助類來完成

這裡因為這裡是三級，所以我就構造了三個輔助類

@Getter
@Setter
public class Data {
    private String value;
    private String label;
    private List<Children> children;
}

@Setter
@Getter
public class Children {
    private String value;
    private String label;
    private List<Children1> children1s;
}
 

@Getter
@Setter
public class Children1 {
    private String label;
    private String value;
}

我的mapper

  //查詢所有的省
    @Select("select * from zone where pid = 1")
    List<ZoneInfo> selectProvince();

    //查詢該省所有的市
    @Select("select * from zone where  pid =#{provinceId}")
    List<ZoneInfo> selectCityByProvinceId(String provinceId);

    //查詢該市對應的縣
    @Select("select * from zone where  pid =#{cityId}")
    List<ZoneInfo> selectCountyByCityId(String cityId);
 

接下來是我的serviceimpl

 @Override
    public Result selectAll() {
        List<Data> dataList = null;
        try {
            dataList = new ArrayList<Data>();
            List<ZoneInfo> provinces = zoneInfoMapper.selectProvince();
            for (ZoneInfo province : provinces) {
                Data data = new Data();
                data.setValue(String.valueOf(province.getId()));
                data.setLabel(province.getDistrict());
                List<ZoneInfo> cities = zoneInfoMapper.selectCityByProvinceId(String.valueOf(province.getId()));
                List<Children> childrenList = new ArrayList<Children>();
                for (ZoneInfo city : cities) {
                    Children children = new Children();

                    children.setLabel(String.valueOf(city.getId()));
                    children.setValue(city.getDistrict());
                    childrenList.add(children);

                    List<ZoneInfo> counties = zoneInfoMapper.selectCountyByCityId(String.valueOf(city.getId()));
                    List<Children1> children1s = new ArrayList<Children1>();
                    for (ZoneInfo county : counties) {
                        Children1 children1 = new Children1();
                        children1.setLabel(String.valueOf(county.getId()));
                        children1.setValue(county.getDistrict());
                        children1s.add(children1);
                    }
                    children.setChildren1s(children1s);

                }
                data.setChildren(childrenList);
                dataList.add(data);
            }
        } catch (Exception e) {
            Logger.logMsg(4, e.getMessage());
            return Result.build(500, ErrorCode.UNKNOWN_ERROR.getStatusMsg());
        }
        return Result.ok(dataList);
    }

這裡需要注意的是

Data data = new Data();需要在for迴圈裡面建立，因為對於不同的province都是一個data,然後每一個data最終新增到datalist裡面。如果是在for迴圈外面例項化，就會被覆蓋掉，導致datalist裡面的資料只有最後一個

同樣的下面的children以及children1也一樣