开发过程中，涉及到多级菜单的应用，找了一些资料案例实现如下（使用springboot+layui+oracle）：

创建菜单表 ：

-- 创建菜单表
create table wxmini_menus(
 menu_id         number unique,   --菜单ID
 menu_name        varchar2(20),
 menu_url        varchar2(200),
 menu_icon        varchar2(100),
 parent_id        number,      --父菜单ID
 status         varchar2(10),
 menu_sort        number,
 last_update_date    DATE not null,
 last_updated_by     NUMBER not null,
 creation_date      DATE not null,
 created_by       NUMBER not null,
 last_update_login    NUMBER
);
 
-- 插入菜单记录
insert into wxmini_menus values((select 1 from dual),'设置',null,null,null,1,100,sysdate,-1,sysdate,-1,-1);
insert into wxmini_menus values((select max(menu_id)+1 from yl_wxmini_menus),'用户',null,null,1,1,null,sysdate,-1,sysdate,-1,-1);
insert into wxmini_menus values((select max(menu_id)+1 from yl_wxmini_menus),'网站用户',null,null,1,1,null,sysdate,-1,sysdate,-1,-1);
insert into wxmini_menus values((select max(menu_id)+1 from yl_wxmini_menus),'角色管理',null,null,1,1,null,sysdate,-1,sysdate,-1,-1);
--主菜单二
insert into wxmini_menus values((select max(menu_id)+1 from yl_wxmini_menus),'主页',null,null,null,1,1,sysdate,-1,sysdate,-1,-1);
insert into wxmini_menus values((select max(menu_id)+1 from yl_wxmini_menus),'控制台',null,null,5,1,null,sysdate,-1,sysdate,-1,-1);
insert into wxmini_menus values((select max(menu_id)+1 from yl_wxmini_menus),'主页一',null,null,5,1,null,sysdate,-1,sysdate,-1,-1);
insert into wxmini_menus values((select max(menu_id)+1 from yl_wxmini_menus),'主页二',null,null,5,1,null,sysdate,-1,sysdate,-1,-1);

实体类 WxMenu.java：

public class WxMenu {
  
  private String menu_id;
  private String menu_name;
  private String menu_url;
  private String menu_icon;
  private String parent_id;
  private String parent_menu_name;
  private String status;
  private String menu_sort;
  private String last_update_date;
  private long last_updated_by;
  private String creation_date;
  private long created_by;
  private long last_update_login;
 
  private List<WxMenu> childMenus;
 
  ......
}
Controller控制层 :
@Controller
@RequestMapping("/index")
public class IndexController {
 
  @Autowired
  private WxUserService wxUserService;
 
  /**
   * 获取所有菜单数据
   * @return
   */
  @ResponseBody
  @RequestMapping(value = "/loadAuthMenus",method = RequestMethod.GET)
  public LayuiJsonFormat<HashMap> login(String username, String password, HttpServletRequest request) {
 
    // 获取所有菜单数据
    List<WxMenu> wxMenus = wxUserService.getAllMenus();
    //定义 存储一级菜单
    List<WxMenu> menuList = new ArrayList<WxMenu>();
    // 先找到所有的一级菜单
    for (int i = 0; i < wxMenus.size(); i++) {
      // 一级菜单没有父菜单，为null
      if (StringUtils.isBlank(wxMenus.get(i).getParent_id())) {
        menuList.add(wxMenus.get(i));
      }
    }
    // for调用递归，循环获取所有子菜单
    for (WxMenu menu : menuList) {
      menu.setChildMenus(getChildmenus(menu.getMenu_id(), wxMenus));
    }
    //存储所有菜单，将数据回传至 layui 前端
    map.put("menus", menuList);
 
    return LayuiJsonFormat.createBySuccess(map.size(),map);
  }
 
 
  /**
   * 递归子菜单
   * @param id
   * @param wxMenus
   * @return
   */
  private List<WxMenu> getChildmenus(String id, List<WxMenu> wxMenus) {
    // 子菜单
    List<WxMenu> childMenus = new ArrayList<>();
    for (WxMenu menu : wxMenus) {
      if (StringUtils.isNotBlank(menu.getParent_id())) {
        if (menu.getParent_id().equals(id)) {
          childMenus.add(menu);
        }
      }
    }
    for (WxMenu menu : childMenus) {
      //数据库动态存储菜单的url,此时判断url为空的，则是节点菜单（存在子菜单）
      if (StringUtils.isBlank(menu.getMenu_url())) {
        // 递归调用
        menu.setChildMenus(getChildmenus(menu.getMenu_id(), wxMenus));
      }
    }
    if (childMenus.size() == 0) {
      return null;
    }
    return childMenus;
  }
}