Java递归算法构造JSON树形结构

Posted 2022-03-18 数通畅联

1.前言

最近项目中有一个需求，数据库中的菜单表是一个常见的id-pid结构，需要把它构建成树形的JSON格式发送给第三方，写出来之后感觉也是很简单的，核心代码只有5行，重要的是思路要明确，这里把源码分享给大家。

工程里面使用了json-lib.jar这个包，作用是将List序列化成JSON。

2.源码

package com.agileai.esb.smc.domain;

 

import java.util.*;

import net.sf.json.JSONArray;

 

public class TreeBuilder

        

         List<TreeBuilder.Node>nodes = newArrayList<TreeBuilder.Node>();

 

         public TreeBuilder(List<Node> nodes)

                   super();

                   this.nodes= nodes;

        

        

         /**

          * 构建JSON树形结构

          * @return

          */

         public String buildJSONTree()

                   List<Node>nodeTree = buildTree();

                   JSONArrayjsonArray = JSONArray.fromObject(nodeTree);

                   return jsonArray.toString();

        

        

         /**

          * 构建树形结构

          * @return

          */

         public List<Node> buildTree()

                   List<Node>treeNodes = newArrayList<Node>();

                   List<Node>rootNodes = getRootNodes();

                   for (Node rootNode : rootNodes)

                            buildChildNodes(rootNode);

                            treeNodes.add(rootNode);

                  

                   return treeNodes;

        

        

         /**

          * 递归子节点

          * @param node

          */

         public voidbuildChildNodes(Node node)

       List<Node> children = getChildNodes(node); 

       if (!children.isEmpty())

            for(Node child : children)

                     buildChildNodes(child);

             

            node.setMenus(children);

       

        

 

         /**

          * 获取父节点下所有的子节点

          * @param nodes

          * @param pnode

          * @return

          */

         public List<Node> getChildNodes(Nodepnode)

                   List<Node>childNodes = newArrayList<Node>();

                   for (Node n : nodes)

                            if (pnode.getId().equals(n.getPid()))

                                     childNodes.add(n);

                           

                  

                   return childNodes;

        

        

         /**

          * 判断是否为根节点

          * @param nodes

          * @param inNode

          * @return

          */

         public booleanrootNode(Node node)

                   boolean isRootNode = true;

                   for (Node n : nodes)

                            if (node.getPid().equals(n.getId()))

                                     isRootNode= false;

                                     break;

                           

                  

                   return isRootNode;

        

        

         /**

          * 获取集合中所有的根节点

          * @param nodes

          * @return

          */

         public List<Node> getRootNodes()

                   List<Node>rootNodes = newArrayList<Node>();

                   for (Node n : nodes)

                            if (rootNode(n))

                                     rootNodes.add(n);

                           

                  

                   return rootNodes;

        

        

         public staticclass Node

                  

                   private String id;

                   private String pid;

                   private String text;

                   private String url;

                   private List<Node> menus;

                  

                   public Node()

 

                   public Node(String id, String pid, Stringtext, String url)

                            super();

                            this.id =id;

                            this.pid =pid;

                            this.text =text;

                            this.url =url;

                  

                  

                   public String getId()

                            return id;

                  

                   public voidsetId(String id)

                            this.id =id;

                  

                   public String getPid()

                            return pid;

                  

                   public voidsetPid(String pid)

                            this.pid =pid;

                  

                   public String getText()

                            return text;

                  

                   public voidsetText(String text)

                            this.text =text;

                  

                   public String getUrl()

                            return url;

                  

                   public voidsetUrl(String url)

                            this.url =url;

                  

                   public List<Node> getMenus()

                            return menus;

                  

                   public voidsetMenus(List<Node> menus)

                            this.menus= menus;

                  

        

        

         public staticvoid main(String[] args)

                  

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

                   Nodep1 = new Node("01", "","01", "");

                   Nodep6 = new Node("02", "","02", "");

                   Nodep7 = new Node("0201", "02","0201", "");

                   Nodep2 = new Node("0101", "01","0101", "");

                   Nodep3 = new Node("0102", "01","0102", "");

                   Nodep4 = new Node("010101", "0101","010101", java中树形结构怎么实现

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