JAVA 树形菜单递归实现（省市区同理）

菜单树形结构

package com.yun.entity.vo;

import io.swagger.annotations.ApiModelProperty;
import lombok.Data;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

@Data
public class MenuVO implements Serializable {

    private static final long serialVersionUID = 1L;

    @ApiModelProperty(value = "主键")
    private Integer id;

    @ApiModelProperty(value = "菜单名称")
    private String name;

    @ApiModelProperty(value = "菜单图标")
    private String icon;

    @ApiModelProperty(value = "菜单路由")
    private String link;

    @ApiModelProperty(value = "菜单索引")
    private String indexTag;

    @ApiModelProperty(value = "菜单类型，目录：12801001，菜单：12801002，按钮：12801003")
    private Integer type;

    @ApiModelProperty(value = "排序")
    private Integer sort;

    @ApiModelProperty(value = "状态，启用：12781001，停用：12781002")
    private Integer status;

    @ApiModelProperty(value = "权限标识")
    private String permission;

    @ApiModelProperty(value = "父节点主键，-1为根节点")
    private Integer parentId;

    @ApiModelProperty(value = "用于前端显示开关，status=12781001为true")
    private boolean enable;

    @ApiModelProperty(value = "菜单子表")
    private List<MenuVO> children = new ArrayList<>();
}

package com.yun.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.yun.constant.DictConstant;
import com.yun.entity.dto.UserDTO;
import com.yun.entity.po.MenuPO;
import com.yun.entity.vo.MenuVO;
import com.yun.mapper.MenuMapper;
import com.yun.service.MenuService;
import org.springframework.beans.BeanUtils;
import org.springframework.stereotype.Service;
import org.springframework.util.CollectionUtils;

import java.util.ArrayList;
import java.util.List;

/**
 * <p>
 * 菜单表 服务实现类
 * </p>
 *
 * @author CNSTT
 * @since 2023-01-21
 */
@Service
public class MenuServiceImpl extends ServiceImpl<MenuMapper, MenuPO> implements MenuService {

    /**
     * 菜单树形查询
     *
     * @param dto 传参
     * @return List<MenuVO>
     */
    @Override
    public List<MenuVO> searchDefault(MenuDTO dto) {
        LambdaQueryWrapper<MenuPO> wrapper = new QueryWrapper<MenuPO>().lambda();
        // 查询菜单或目录
        wrapper.in(MenuPO::getType, DictConstant.DICT_MENU_TYPE_CATALOG, DictConstant.DICT_MENU_TYPE_MENU);
        wrapper.eq(MenuPO::getDeleteFlag, DictConstant.DICT_NO);
        List<MenuPO> menuList = baseMapper.selectList(wrapper);
        if (!CollectionUtils.isEmpty(menuList)) {
            // 树形返回
            return packageListFunc(menuList);
        }
        return new ArrayList<>();
    }

    /**
     * 组装菜单树形结构主方法
     *
     * @param menuList 全量数据
     * @return List<MenuVO>
     */
    private List<MenuVO> packageListFunc(List<MenuPO> menuList) {
        List<MenuVO> result = new ArrayList<>();
        List<MenuVO> list = convertResult(menuList);

        for (MenuVO node : list) {
            // parentId = -1为顶层目录或菜单
            if (node.getParentId() == -1) {
                result.add(findChildren(node, list));
            }
        }
        return result;
    }

    /**
     * 递归查询 - 根据父节点获取子节点
     *
     * @param node 父节点
     * @param result 全量数据
     * @return MenuVO 填充完父节点
     */
    private MenuVO findChildren(MenuVO node, List<MenuVO> result) {
        for (MenuVO dto : result) {
            // 父节点的ID等于子节点的父节点ID
            if (node.getId().equals(dto.getParentId())) {
                if (node.getChildren() == null) {
                    node.setChildren(new ArrayList<>());
                }
                node.getChildren().add(findChildren(dto, result));
            }
        }
        return node;
    }

    /**
     * 公共方法 - 实体转化VO出参集合
     *
     * @param menuList PO结果集
     * @return List<MenuVO>
     */
    private List<MenuVO> convertResult(List<MenuPO> menuList) {
        List<MenuVO> result = new ArrayList<>();
        if (!CollectionUtils.isEmpty(menuList)) {
            menuList.forEach(menuPO -> {
                MenuVO vo = new MenuVO();
                BeanUtils.copyProperties(menuPO, vo);
                vo.setEnable(vo.getStatus() != null && vo.getStatus() == DictConstant.DICT_YES);
                result.add(vo);
            });
        }
        return result;
    }
}