联合MyBatis,由Map获取

源码如下

package com.zl.demo;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Java递归获取TreeJson
 * @author ZhangLi
 * @date 2019年6月18日 上午11:10:45
 * @WeiXin zl4828
 * @备注 沫沫金原创提供,仅供参考
 */
public class TreeJson {
    public static void main(String[] args) {
        TreeJson treeJson = new TreeJson();
        treeJson.treeMap.add(new HashMap<String, Object>(){{
            put("ID","0");
            put("NAME","根节点");
            put("PID","null");
        }});
        treeJson.treeMap.add(new HashMap<String, Object>(){{
            put("ID","1");
            put("NAME","节点1");
            put("PID","0");
        }});
        treeJson.treeMap.add(new HashMap<String, Object>(){{
            put("ID","2");
            put("NAME","节点2");
            put("PID","0");
        }});
        treeJson.treeMap.add(new HashMap<String, Object>(){{
            put("ID","3");
            put("NAME","节点3");
            put("PID","0");
        }});
        treeJson.treeMap.add(new HashMap<String, Object>(){{
            put("ID","11");
            put("NAME","节点11");
            put("PID","1");
        }});
        treeJson.treeMap.add(new HashMap<String, Object>(){{
            put("ID","12");
            put("NAME","节点12");
            put("PID","1");
        }});
        treeJson.treeMap.add(new HashMap<String, Object>(){{
            put("ID","13");
            put("NAME","节点13");
            put("PID","1");
        }});
        System.out.println(treeJson.recursiveTree("0"));
    }

    private List<Map<String, Object>> treeMap = new ArrayList<Map<String, Object>>();  //全局变量

    /**
     * 递归算法解析成树形结构
     * @param pid
     */
    public Map recursiveTree(String pid) {
        Map node = getNodeById(pid);
        List<Map<String, Object>> childrenList = new ArrayList<Map<String, Object>>();
        if(null==node){
            return node;
        }
        List<Map<String, Object>> childTreeNodes  = getChildTreeById(pid);
        for(Map child : childTreeNodes){
            Map n = recursiveTree(String.valueOf(child.get("ID")));
            childrenList.add(n);
        }
        node.put("children",childrenList);
        return node;
    }

    /**
     * 根据pid查询节点对象
     */
    public Map getNodeById(String pid){
        for (Map node : treeMap) {
            if(null != pid){
                if (pid.equals(node.get("ID"))) {
                    return node;
                }
            }
        }
        return null;
    }
    /**
     * 根据父节点pid获取所有了节点
     */
    public List<Map<String, Object>> getChildTreeById(String pid){
        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
        if(null != treeMap){
            for (Map node : treeMap) {
                if(null != pid){
                    if (pid.equals(node.get("PID"))) {
                        list.add(node);
                    }
                }
            }
        }
        return list;
    }

}

应用场景
例如,Echarts树形图形
Java递归获得TreeJson

注意,使用JSON转换

{
    name: '根节点',
    pid: null,
    id: 0,
    children: [{
        name: '节点1',
        pid: 0,
        id: 1,
        children: [{
            name: '节点11',
            pid: 1,
            id: 11,
            children: []
        }, {
            name: '节点12',
            pid: 1,
            id: 12,
            children: []
        }, {
            name: '节点13',
            pid: 1,
            id: 13,
            children: []
        }]
    }, {
        name: '节点2',
        pid: 0,
        id: 2,
        children: []
    }, {
        name: '节点3',
        pid: 0,
        id: 3,
        children: []
    }]
};

以上,拷贝本地运行,任意应用。