关于json树的处理（mui的三级联动需要的是json树形式的数据）

我就是我 2022-01-09 16:21 143阅读 0赞

## 原文代码连接 ##

[阿里fastjson将集合转为树形结构][fastjson]

package com.etoak.test;
    
    
    
    import com.alibaba.fastjson.JSON;
    import com.alibaba.fastjson.JSONArray;
    import com.alibaba.fastjson.JSONObject;
    
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    /**
     * Created by wen on 2019/6/20.
     */
    public class Test {
        public static void main(String[] args) {
            List<Map<String, Object>> data = new ArrayList<>();
            Map<String, Object> map = new HashMap<>();
            map.put("id", 1);
            map.put("pid", 0);
            map.put("name", "甘肃省");
            data.add(map);
            Map<String, Object> map2 = new HashMap<>();
            map2.put("id", 2);
            map2.put("pid", 1);
            map2.put("name", "天水市");
            data.add(map2);
            Map<String, Object> map3 = new HashMap<>();
            map3.put("id", 3);
            map3.put("pid", 2);
            map3.put("name", "秦州区");
            data.add(map3);
            Map<String, Object> map4 = new HashMap<>();
            map4.put("id", 4);
            map4.put("pid", 0);
            map4.put("name", "北京市");
            data.add(map4);
            Map<String, Object> map5 = new HashMap<>();
            map5.put("id", 5);
            map5.put("pid", 4);
            map5.put("name", "昌平区");
            data.add(map5);
            //System.out.println(JSON.toJSONString(data));
            JSONArray result = listToTree(JSONArray.parseArray(JSON.toJSONString(data)), "id", "pid", "children");
            //System.out.println(JSON.toJSONString(result));
        }
        public static JSONArray listToTree(JSONArray arr,String id,String pid,String child){
            JSONArray r = new JSONArray();
            JSONObject hash = new JSONObject();
            //将数组转为Object的形式，key为数组中的id
            for(int i=0;i<arr.size();i++){
                JSONObject json = (JSONObject) arr.get(i);
                hash.put(json.getString(id), json);
            }
    
            //遍历结果集
            for(int j=0;j<arr.size();j++){
                System.out.println("此轮Hash:"+hash);
                System.out.println("此轮arr:"+arr);
                //单条记录
                JSONObject aVal = (JSONObject) arr.get(j);
                System.out.println("初始的aVal:"+aVal);
                //在hash中取出key为单条记录中pid的值
                JSONObject hashVP = (JSONObject) hash.get(aVal.get(pid).toString());
                System.out.println("初始的hashVP："+hashVP);
    
                //如果记录的pid存在，则说明它有父节点，将她添加到孩子节点的集合中
                if(hashVP!=null){
                    System.out.println("hashVP不为空进行操作");
                    //检查是否有child属性
                    if(hashVP.get(child)!=null){
                        System.out.println("有孩子");
                        JSONArray ch = (JSONArray) hashVP.get(child);
                        ch.add(aVal);
                        hashVP.put(child, ch);
                    }else{
                        System.out.println("没孩子");
                        JSONArray ch = new JSONArray();
                        ch.add(aVal);
                        hashVP.put(child, ch);
                    }
    
                }else{
                    System.out.println("hashVP为空直接r添加");
    
                    r.add(aVal);
    
                }
                System.out.println("变化后的hashVP:"+hashVP);
                System.out.println("最后的对象是："+r);
    
                System.out.println("=====");
            }
            return r;
        }
    }

**需要的数据格式如下：**

[          {
    				value: '0',
    				text: '南京市',
    				children: [{
    					value: "1",
    					text: "某某区",
    					children: [{
    						value: "2",
    						text: "街道1"
    					}, {
    						value: "3",
    						text: "街道2"
    					}, {
    						value: "4",
    						text: "街道3"
    					}],
    				   },{
    							value: "5",
    							text: "某某区",
    							children: [{
    								value: "6",
    								text: "街道1"
    							}, {
    								value: "7",
    								text: "街道2"
    							}, {
    								value: "8",
    								text: "街道3"
    							}],
    				      }],
    
    			}]

**用到了Alibaba的fastJson**

[fastjson]: https://blog.csdn.net/qq_35131811/article/details/80652670