Same level of list data into multi-level json

Internet search a lot of information still have not found what I wanted, and then wrote a front-end js recursive data will show up.

Raw data

After the data in the database query is out of this format, in order that the multi-level data into json data format to determine the relationship between parent and child nodes based on the id and parentID therein.

getJsonTree function = var (JSONView, the parentId) { 
    var itemArr = {}; 
    var = In Flag to true; // switch statement 
    for (var I = 0; I <jsonView.length; I ++) { 
        var Node = JSONView [I]; 
        IF (== node.parentId the parentId) { 
            In Flag to false =; 
            var = node.fieldName the fieldName; 
            var = getJsonTree the newNode (JSONView, node.id); 
            itemArr [the fieldName] = the newNode; 
        } 
    } 
    IF (In Flag) { 
        return null; 
    } 
    return [itemArr]; 
} 
using a recursive algorithm to traverse all of the data is formed out of the multi-level json, then a third-party plug-ins can use its data format jsonView.js

This method is not very good, because I have more than four pieces of data so that each piece of data to traverse it again, so there is a big problem, and that is the problem traversal time, this uses a time for space , resulting in a great waste of time.

The second method I ask one of my seniors, using java to write a recursive algorithm will turn into a multi-level json.

public String list(ModelMap modelMap) {
    List<IcdsOriginalField> icdsOriginalFields = icdsOriginalFieldService.selectJson();

Map<String, IcdsOriginalField> parents = new HashMap<>();

  Map<String, List<IcdsOriginalField>> childs = new HashMap<>();
  if(icdsOriginalFields!=null && icdsOriginalFields.size()>0) {
      for(IcdsOriginalField item : icdsOriginalFields) {
          parents.put(item.getId().toString(), item);
          String pid = item.getParentId() != null ? item.getParentId().toString(): "0";
          if(childs.get(pid) != null ) {
              childs.get(pid).add(item);
          }else {
              List<IcdsOriginalField> temp = new ArrayList<>();
              temp.add(item);
              childs.put(pid,temp);
          }
      }
  }
  List<Object> json = diGuiOpt("0", childs);
//SerializerFeature.WriteMapNullValue This is the time to address data is empty continue to write "null"

  modelMap.put ( "jsonView", JSONObject.toJSONString ( json, SerializerFeature.WriteMapNullValue)); // this is a return to the front page of data to 
} 
method basically Thus, when the front and rear ends of data transmission according to their own programs to decide

public List<Object> diGuiOpt(String pid, Map<String, List<IcdsOriginalField>> childrens){
    List<IcdsOriginalField> childs = childrens.get(pid);
    Map<String, Object> temp = null;
    if(childs != null && childs.size() > 0) {
        temp = new HashMap<>();
        for (IcdsOriginalField item : childs) {
            String id = item.getId().toString();
            if(childrens.get(id)!= null && childrens.get(id).size()>0) {
                temp.put(item.getFieldName(),diGuiOpt(id, childrens));
            } else {
                temp.put(item.getFieldName(),null);
            }
        }
    } else {
        return null;
    }
    List<Object> result = new ArrayList<>();
    result.add(temp);
    return result;
}