java 递归菜单树（详细）

不念不忘少年蓝@ 2023-06-22 13:46 317阅读 0赞

## 1.表结构 ##

SET FOREIGN_KEY_CHECKS=0;
    
    -- ----------------------------
    -- Table structure for menu
    -- ----------------------------
    DROP TABLE IF EXISTS `menu`;
    CREATE TABLE `menu` (
      `id` int(11) NOT NULL AUTO_INCREMENT,
      `menu_name` varchar(64) NOT NULL COMMENT '菜单名称',
      `order_num` int(11) DEFAULT NULL COMMENT '菜单顺序',
      `url` varchar(64) DEFAULT NULL COMMENT '菜单路径',
      `pid` varchar(11) DEFAULT NULL COMMENT '上级Id',
      `icon` varchar(255) DEFAULT NULL COMMENT '菜单图标',
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;
    
    -- ----------------------------
    -- Records of menu
    -- ----------------------------
    INSERT INTO `menu` VALUES ('1', '系统管理', '1', '', '0', null);
    INSERT INTO `menu` VALUES ('2', '轨迹查询', '2', '', '0', null);
    INSERT INTO `menu` VALUES ('3', '设备信息', '3', '', '0', null);
    INSERT INTO `menu` VALUES ('4', '用户信息', '1', '', '1', null);
    INSERT INTO `menu` VALUES ('5', '客户信息', '2', null, '1', null);
    INSERT INTO `menu` VALUES ('6', '用户资料', '1', null, '4', null);
    INSERT INTO `menu` VALUES ('7', '客户资料', '1', null, '5', null);
    INSERT INTO `menu` VALUES ('8', '切割机', '1', null, '3', null);
    INSERT INTO `menu` VALUES ('9', '铲车', '2', null, '3', null);
    INSERT INTO `menu` VALUES ('10', '割片', '1', null, '8', null);

## 2.菜单实体类 ##

import lombok.Data;
    import java.io.Serializable;
    import java.util.List;
    import javax.persistence.*;
    
    
    /** * * @author m * @email 123456789@qq.com * @date 2019-12-13 16:54:59 */
    @Data
    @Table(name = "menu")
    public class Menu implements Serializable { 
    	private static final long serialVersionUID = 1L;
    	
    	//
        @Id
        private Integer id;
    	
        //菜单名称
        @Column(name = "menu_name")
        private String menuName;
    	
        //菜单顺序
        @Column(name = "order_num")
        private Integer orderNum;
    	
        //菜单路径
        @Column(name = "url")
        private String url;
    	
        //上级Id
        @Column(name = "pid")
        private String pid;
    	
        //菜单图标
        @Column(name = "icon")
        private String icon;
    
    	//子菜单
    	@Transient
    	private List<Menu> children;
    
    
    }

## 3.菜单树 ##

/** * 获取菜单树 * @return */
        public List<Menu> menuTree() { 
            //查询所有菜单
            List<Menu> menus = mapper.selectAll();
            //返回的菜单树
            List<Menu> rootMenus = new ArrayList<>();
            for (Menu menu : menus) { 
                //pid（上级Id）为0的是根菜单
                if ("0".equals(menu.getPid())) { 
                    rootMenus.add(menu);
                }
            }
            //遍历，找到二级菜单（根菜单的id和所有菜单中的pid比较）
            for (Menu rootMenu : rootMenus) { 
                List<Menu> child = getChild(String.valueOf(rootMenu.getId()), menus);
                rootMenu.setChildren(child);
            }
            return rootMenus;
        }
    
    
        /** * 递归获取下级菜单 * @param pid 上级Id * @param menus 所有菜单 * @return */
        public List<Menu> getChild(String pid, List<Menu> menus) { 
            //子菜单列表
            List<Menu> childList = new ArrayList<>();
            for (Menu menu : menus) { 
                if (pid.equals(menu.getPid())) { 
                    childList.add(menu);
                }
            }
            //遍历 获取子菜单的子菜单
            for (Menu menu : childList) { 
                List<Menu> child = getChild(String.valueOf(menu.getId()), menus);
                menu.setChildren(child);
            }
            //递归出口 childList长度为0
            if (childList.size() == 0) { 
                return new ArrayList<>();
            }
            return childList;
        }

## 4.测试 ##

{ 
        "status": 200,
        "message": "操作成功",
        "data": [
            { 
                "id": 1,
                "menuName": "系统管理",
                "orderNum": 1,
                "url": "",
                "pid": "0",
                "icon": null,
                "children": [
                    { 
                        "id": 4,
                        "menuName": "用户信息",
                        "orderNum": 1,
                        "url": "",
                        "pid": "1",
                        "icon": null,
                        "children": [
                            { 
                                "id": 6,
                                "menuName": "用户资料",
                                "orderNum": 1,
                                "url": null,
                                "pid": "4",
                                "icon": null,
                                "children": []
                            }
                        ]
                    },
                    { 
                        "id": 5,
                        "menuName": "客户信息",
                        "orderNum": 2,
                        "url": null,
                        "pid": "1",
                        "icon": null,
                        "children": [
                            { 
                                "id": 7,
                                "menuName": "客户资料",
                                "orderNum": 1,
                                "url": null,
                                "pid": "5",
                                "icon": null,
                                "children": []
                            }
                        ]
                    }
                ]
            },
            { 
                "id": 2,
                "menuName": "轨迹查询",
                "orderNum": 2,
                "url": "",
                "pid": "0",
                "icon": null,
                "children": []
            },
            { 
                "id": 3,
                "menuName": "设备信息",
                "orderNum": 3,
                "url": "",
                "pid": "0",
                "icon": null,
                "children": [
                    { 
                        "id": 8,
                        "menuName": "切割机",
                        "orderNum": 1,
                        "url": null,
                        "pid": "3",
                        "icon": null,
                        "children": [
                            { 
                                "id": 10,
                                "menuName": "割片",
                                "orderNum": 1,
                                "url": null,
                                "pid": "8",
                                "icon": null,
                                "children": []
                            }
                        ]
                    },
                    { 
                        "id": 9,
                        "menuName": "铲车",
                        "orderNum": 2,
                        "url": null,
                        "pid": "3",
                        "icon": null,
                        "children": []
                    }
                ]
            }
        ]
    }

## 5.菜单树工具类 ##

[菜单树工具类][Link 1]

[Link 1]: https://blog.csdn.net/weixin_42740530/article/details/103564440