Java查询菜单树形结构

1.创建最简单的菜单数据结构

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- Table structure for t_menu
-- ----------------------------
DROP TABLE IF EXISTS `t_menu`;
CREATE TABLE `t_menu` (
  `id` int(20) NOT NULL AUTO_INCREMENT COMMENT '菜单id',
  `name` varchar(255) DEFAULT NULL COMMENT '菜单名称',
  `icon` varchar(255) DEFAULT NULL COMMENT '图标',
  `path` varchar(255) DEFAULT NULL COMMENT '路径',
  `types` varchar(255) DEFAULT NULL COMMENT '菜单类型:Folder目录/Link页面',
  `parent_id` int(20) DEFAULT NULL COMMENT '父菜单名称',
  `seq` int(10) DEFAULT NULL COMMENT '排序',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=110203 DEFAULT CHARSET=utf8mb4;

-- ----------------------------
-- Records of t_menu
-- ----------------------------
INSERT INTO `t_menu` VALUES ('10', '首页', 'icon', '/index', 'Link', '0', '1');
INSERT INTO `t_menu` VALUES ('11', '菜单1', 'icon', '/m1', 'Folder', '0', '2');
INSERT INTO `t_menu` VALUES ('12', '菜单2', 'icon', '/m2', 'Folder', '0', '3');
INSERT INTO `t_menu` VALUES ('13', '菜单3', 'icon', '/m3', 'Folder', '0', '4');
INSERT INTO `t_menu` VALUES ('1101', '菜单1子菜单1', 'icon', '/m1/m1', 'Folder', '11', '1');
INSERT INTO `t_menu` VALUES ('1102', '菜单1子菜单2', 'icon', '/m1/m2', 'Folder', '11', '2');
INSERT INTO `t_menu` VALUES ('1201', '菜单2页面1', 'icon', '/m2/p1', 'Link', '12', '1');
INSERT INTO `t_menu` VALUES ('1202', '菜单2页面2', 'icon', '/m2/p2', 'Link', '12', '2');
INSERT INTO `t_menu` VALUES ('1301', '菜单3页面1', 'icon', '/m3/p1', 'Link', '13', '1');
INSERT INTO `t_menu` VALUES ('110101', '菜单1子菜单1页面1', 'icon', '/m1/m1/p1', 'Link', '1101', '1');
INSERT INTO `t_menu` VALUES ('110102', '菜单1子菜单1页面2', 'icon', '/m1/m1/p2', 'Link', '1101', '2');
INSERT INTO `t_menu` VALUES ('110103', '菜单1子菜单1页面3', 'icon', '/m1/m1/p3', 'Link', '1101', '3');
INSERT INTO `t_menu` VALUES ('110201', '菜单1子菜单2页面1', 'icon', '/m1/m2/p1', 'Link', '1102', '1');
INSERT INTO `t_menu` VALUES ('110202', '菜单1子菜单2页面2', 'icon', '/m1/m2/p2', 'Link', '1102', '2');

2.Java递归查询

@Override
public List<MenuTree> queryTree() {
    MenuExample example = new MenuExample();
    example.setOrderByClause("seq ASC");
    List<Menu> menuList = menuMapper.selectByExample(example);
    Integer parentId = 0;
    return this.build(menuList, parentId);
}

//递归查子菜单
private List<MenuTree> build(List<Menu> menuList, Integer parentId) {
    return menuList.stream().filter(menu -> menu.getParentId().intValue() == parentId.intValue()).map(menu -> {
        MenuTree menuTree = BeansUtil.convert(menu, MenuTree.class);
        List<MenuTree> childList = build(menuList, menuTree.getId());
        if (childList != null && childList.size() > 0) {
            menuTree.setChildren(childList);
        }
        return menuTree;
    }).collect(Collectors.toList());
}

3.查询结果

{
  "code": "0",
  "msg": "",
  "data": [
    {
      "id": 10,
      "name": "首页",
      "icon": "icon",
      "path": "/index",
      "types": "Link",
      "parentId": 0,
      "seq": 1
    },
    {
      "id": 11,
      "name": "菜单1",
      "icon": "icon",
      "path": "/m1",
      "types": "Folder",
      "parentId": 0,
      "seq": 2,
      "children": [
        {
          "id": 1101,
          "name": "菜单1子菜单1",
          "icon": "icon",
          "path": "/m1/m1",
          "types": "Folder",
          "parentId": 11,
          "seq": 1,
          "children": [
            {
              "id": 110101,
              "name": "菜单1子菜单1页面1",
              "icon": "icon",
              "path": "/m1/m1/p1",
              "types": "Link",
              "parentId": 1101,
              "seq": 1
            },
            {
              "id": 110102,
              "name": "菜单1子菜单1页面2",
              "icon": "icon",
              "path": "/m1/m1/p2",
              "types": "Link",
              "parentId": 1101,
              "seq": 2
            },
            {
              "id": 110103,
              "name": "菜单1子菜单1页面3",
              "icon": "icon",
              "path": "/m1/m1/p3",
              "types": "Link",
              "parentId": 1101,
              "seq": 3
            }
          ]
        },
        {
          "id": 1102,
          "name": "菜单1子菜单2",
          "icon": "icon",
          "path": "/m1/m2",
          "types": "Folder",
          "parentId": 11,
          "seq": 2,
          "children": [
            {
              "id": 110201,
              "name": "菜单1子菜单2页面1",
              "icon": "icon",
              "path": "/m1/m2/p1",
              "types": "Link",
              "parentId": 1102,
              "seq": 1
            },
            {
              "id": 110202,
              "name": "菜单1子菜单2页面2",
              "icon": "icon",
              "path": "/m1/m2/p2",
              "types": "Link",
              "parentId": 1102,
              "seq": 2
            }
          ]
        }
      ]
    },
    {
      "id": 12,
      "name": "菜单2",
      "icon": "icon",
      "path": "/m2",
      "types": "Folder",
      "parentId": 0,
      "seq": 3,
      "children": [
        {
          "id": 1201,
          "name": "菜单2页面1",
          "icon": "icon",
          "path": "/m2/p1",
          "types": "Link",
          "parentId": 12,
          "seq": 1
        },
        {
          "id": 1202,
          "name": "菜单2页面2",
          "icon": "icon",
          "path": "/m2/p2",
          "types": "Link",
          "parentId": 12,
          "seq": 2
        }
      ]
    },
    {
      "id": 13,
      "name": "菜单3",
      "icon": "icon",
      "path": "/m3",
      "types": "Folder",
      "parentId": 0,
      "seq": 4,
      "children": [
        {
          "id": 1301,
          "name": "菜单3页面1",
          "icon": "icon",
          "path": "/m3/p1",
          "types": "Link",
          "parentId": 13,
          "seq": 1
        }
      ]
    }
  ],
  "times": 1577683755976
}