Java reads the menu from the database, recursively builds the menu tree

First look at the menu.

According to this, we define the menu class

public Span class= "Hljs-keyword" >class menu {//menu ID private String    Id //menu name private String name; //parent menu ID private String parentid; //menu URL private String URL; //menu icon private String icon; //menu order private int order; //submenu private list<menu> Childmenus; //... Omit getter and setter methods and ToString Method}             

We define the database based on this class and insert the menu data

DROPTABLEIFEXISTS' Jrbac_menu ';CREATETABLE' Jrbac_menu ' (' ID 'varchar32)NotNULL COMMENT' PRIMARY key id,uuid32 bit ',' Name 'varchar64)NotNULL COMMENT' Login user name ',' parent_id 'varchar32)DEFAULTNULL COMMENT' Parent menu ID ',' URL 'varchar64)DEFAULTNULL COMMENT' Access address ',' Icon 'varchar32)DEFAULTNULL COMMENT' Menu Icon ',' Order ' tinyint (4)DEFAULT' 0 ' COMMENT' Menu Order ',PRIMARYKEY (' ID ')) engine=innodbDEFAULT Charset=utf8 comment=' Menu table ';-- ------------------------------Records of Jrbac_menu-- ----------------------------INSERTInto' Jrbac_menu 'VALUES (' 1 ',' Forms ',Null' Forms.html ',' FA Fa-edit ',' 0 ');INSERTInto' Jrbac_menu 'VALUES (' 2 ',' UI Elements ',Null‘‘,' FA Fa-wrench ',' 1 ');INSERTInto' Jrbac_menu 'VALUES (' 3 ',' Buttons ',' 2 ',' Buttons.html ',‘‘,' 0 ');INSERTInto' Jrbac_menu 'VALUES (' 4 ',' Icons ',' 2 ',' Icons.html ',Null' 1 ');INSERTInto' Jrbac_menu 'VALUES (' 5 ',' Multi-level Dropdown ',‘‘,‘‘,' FA Fa-sitemap ',' 2 ');INSERTInto' Jrbac_menu 'VALUES (' 6 ',' Second level Item ',' 5 ',' Second.html ',null,  ' 0 '); insert INTO  Jrbac_menu ' values ( ' 7 ',  ' third level ',  ' 5 ', null, ",  ' 1 '); insert INTO  Jrbac_menu ' values ( ' 8 ',  ' third level Item ',  ' 7 ',  ' third.html ', Span class= "Hljs-keyword" >null,  ' 0 ');         

In order to demonstrate, we have not finished the expandable, just insert a few data can be effective.

Test method and Recursive method

PrivateFinal Gson Gson =New Gsonbuilder (). disablehtmlescaping (). Create ();@TestPublicvoidTestquerymenulist () {Raw data list<menu> Rootmenu = Menudao.querymenulist (NULL);View Resultsfor (menu menu:rootmenu) {System.out.println (menu);}The final result list<menu> Menulist =New Arraylist<menu> ();Find all the first level menusfor (int i =0; I < rootmenu.size (); i++) {The first level menu has no parentidif (Stringutils.isblank (Rootmenu.get (i). Getparentid ())) {Menulist.add (Rootmenu.get (i));}}To set a submenu for a one-level menu, Getchild is called recursivelyfor (Menu menu:menulist) {Menu.setchildmenus (Getchild (Menu.getid (), Rootmenu));} Map<string,object> Jsonmap =New Hashmap<> (); Jsonmap.put ("Menu", menulist); System.out.println (Gson.tojson (Jsonmap));}/** * Recursive Lookup submenu * *@param ID * Current Menu ID *@param rootmenu * List to find *@return */Private list<menu>Getchild (String ID, list<menu> rootmenu) {Sub-menu List<menu> childlist =new arraylist<> (); for (menu menu:rootmenu) {//traverse all nodes, comparing the parent menu ID to the passed-in ID if (Stringutils.isnotblank (Menu.getparentid ())) {if ( Menu.getparentid (). Equals (ID)) {childlist.add (menu);}} } //the submenu of the handle menu cycle again for (menu menu:childlist) {//no URL submenu also has submenu if (Stringutils.isblank (Menu.geturl ())) {//Recursive Menu.setchildmenus (Getchild (Menu.getid (), rootmenu)); }} //recursive exit condition if (childlist.size () = = 0) {return null;} return childlist;}             

Menudao.querymenulist (null); The result of a lookup is one piece of data

Meudao

package com.jrbac.dao;import java.util.List;import com.jrbac.entity.LoginUser;import com.jrbac.entity.Menu;public interface MenuDao { /** * 查找用户的菜单 * @param loginUser * @return */ public List<Menu> queryMenuList(LoginUser loginUser);}

MyBatis

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.jrbac.dao.MenuDao"> <select id="queryMenuList" resultType="Menu"> SELECT id,`name`,parent_id,url,icon,`order` FROM jrbac_menu ORDER BY `order` ASC </select></mapper>

Test the running result of the program and compare the output JSON to the formatted one

Java reads the menu from the database, recursively builds the menu tree