将平面列表转换为层次结构列表，然后将其转换为JSON

Question

I'm having some trouble converting a "flat" list to a hierarchy list.

The orignal list only knows who the parent is but I would like to convert so that it knows who its children are instead, also preferably sort it at the same time so that they get added to the list in the order of

1.1 Parent 
      2.2 Child
               3.3 Child
                        4.4 Child
      2.5 Child
               3.6 Child
1.7 Parent
      2.8 Child

This is what I've got atm. This however only works for down to 2 levels, I want some method which works no matter how deep it has to go.

    System.out.println("Trying to sort the list so that things get added in the order of 1. parent -> 2. children ");
    for(int i = 0; i < arrayListUnsorted.size() ; i++){
            if(arrayListUnsorted.get(i).getParent().equals("#")){
                arrayListSorted.add(arrayListUnsorted.get(i));
                arrayListUnsorted.remove(i);
            }
    }

    for(int a = 0; a < arrayListSorted.size(); a++){
        for(int b = 0; b < arrayListUnsorted.size(); b++){
            if(Integer.toString(arrayListSorted.get(a).getId()).equals(arrayListUnsorted.get(b).getParent())){
                arrayListSorted.add(arrayListUnsorted.get(b));
                arrayListUnsorted.remove(b);
            }

        }
    }   

Model:

public class TreeBranchModel {

private int id;
private String text;
private String parent;

public TreeBranchModel(int id, String text, String parent) {
    super();
    this.id = id;
    this.text = text;
    this.parent = parent;
}
*Getters/Setters*

Model to be converted to:

public class TreeBranchModelHeirachy {

private int id;
private String text;
private ArrayList<TreeBranchModelHeirachy> children;

public TreeBranchModelHeirachy(int id, String text, ArrayList<TreeBranchModelHeirachy> children) {
    super();
    this.id = id;
    this.text = text;
    this.children = children;
}
*Getters/Setters*

Any help is greatly appreciated.

Answer 1

Please use the following code implemented using Gson library

import java.lang.reflect.Field;
import java.util.List;
import com.google.gson.ExclusionStrategy;
import com.google.gson.FieldAttributes;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
public class JsonConvertor {

private static GsonBuilder gsonBuilder;
private static Gson gson;

private JsonConvertor() {

}
public static Object fromJson(String json, Class clz)
{
    gson=new Gson();
    return gson.fromJson(json,clz);
}

public static String toJson(Object obj) {
    gsonBuilder = new GsonBuilder();
    gsonBuilder = gsonBuilder
            .addSerializationExclusionStrategy(new CustomIclusionStrategy(
                    obj.getClass()));
    gson = gsonBuilder.create();
    String json = gson.toJson(obj);
    return json;
 }

}

class CustomIclusionStrategy implements ExclusionStrategy {

private Class classToIclude;

private Field[] declaredFields;


private List<FieldAttributes> fields;

public CustomIclusionStrategy(List<FieldAttributes> fields) {
    this.fields = fields;
}

public CustomIclusionStrategy(Class classToIclude) {
    this.classToIclude = classToIclude;
    this.declaredFields=classToIclude.getDeclaredFields();

}

// called only if shouldSkipClass returns false
@Override
public boolean shouldSkipField(FieldAttributes f) {

    try {
        classToIclude.getSuperclass().getDeclaredField(f.getName());
        System.out.println(f.getName());
        return true;
    } catch (Exception e) {
    } 
    return false;

}

@Override
public boolean shouldSkipClass(Class<?> clazz) {
    // if returns false shouldSkipField will be called,
// otherwise shouldSkipField will not be called
    return false;
}

}

import java.util.ArrayList;
import java.util.List;


public class Node {

String id;
String name;
String data;
List<Node> children;
public String getId() {
    return id;
}
public void setId(String id) {
    this.id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public String getData() {
    return data;
}
public void setData(String data) {
    this.data = data;
}
public List<Node> getChildren() {
    return children;
}
public void setChildren(List<Node> children) {
    this.children = children;
}

public String toJson()
{
    return JsonConvertor.toJson(this);
}

public Node(String id, String name, String data) {
    super();
    this.id = id;
    this.name = name;
    this.data = data;
}
public Node(String id, String name, String data, List<Node> children) {
    super();
    this.id = id;
    this.name = name;
    this.data = data;
    this.children = children;
}
public static void main(String[] args) {

    List<Node> list=new ArrayList<Node>();

    Node n2=new Node("2","n2","d2");
    Node n3=new Node("3","n3","d3");
    Node n4=new Node("4","n4","d4");
    list.add(n2);
    list.add(n3);
    list.add(n4);

    Node n1=new Node("1","n1","d1",list);
    System.out.println(n1.toJson());
}

}

This is the output:

 {"id":"1","name":"n1","data":"d1","children":[{"id":"2","name":"n2","data":"d2"},{"id":"3","name":"n3","data":"d3"},{"id":"4","name":"n4","data":"d4"}]}