Java如何使用递归查询多级树形结构数据(多级菜单)

package org.jeecg.modules.system.entity;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import com.fasterxml.jackson.annotation.JsonFormat;
import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.experimental.Accessors;
import org.springframework.format.annotation.DateTimeFormat;
import java.util.Date;
import java.util.List;

@Data
@TableName("sys_depart_Manage")
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
@ApiModel(value="部门对象", description="部门对象")
public class SysDepartManage {
	
	/**部门名称*/
    @ApiModelProperty(value = "部门名称")
	private String departName;

	/**资源id*/
	@ApiModelProperty(value = "资源id")
	@TableId(type = IdType.AUTO)
	private Integer resourceId;

	/**父id*/
	@ApiModelProperty(value = "父id")
	private String parentId;

	/**是否展示*/
	@ApiModelProperty(value = "是否展示")
	private Integer showInput;


	/**创建时间*/
	@JsonFormat(timezone = "GMT+8",pattern = "yyyy-MM-dd HH:mm:ss")
    @DateTimeFormat(pattern="yyyy-MM-dd HH:mm:ss")
    @ApiModelProperty(value = "创建时间")
	private Date createTime;

	/**更新时间*/
	@JsonFormat(timezone = "GMT+8",pattern = "yyyy-MM-dd HH:mm:ss")
    @DateTimeFormat(pattern="yyyy-MM-dd HH:mm:ss")
    @ApiModelProperty(value = "更新时间")
	private Date updateTime;

	/** 子类菜单数据 */
	@TableField(exist = false)
	private List<SysDepartManage> childMenu;

}

	@Resource
    private ISysDepartManageService sysDepartManageService;
	/**
     * 部门树形查询
     * @param parentID
     * @return
     */
    @GetMapping("/menu")
    @ApiOperation(value="部门树形查询", notes="部门树形查询")
    public List<SysDepartManage> findMenu(@RequestParam String parentID) {
        return sysDepartManageService.findMenu(parentID);
    }

package org.jeecg.modules.system.service;

import com.baomidou.mybatisplus.extension.service.IService;
import org.jeecg.modules.system.entity.SysDepartManage;
import java.util.List;
import java.util.Map;

public interface ISysDepartManageService extends IService<SysDepartManage> {

    List<SysDepartManage> findMenu(String parentID );

}

package org.jeecg.modules.system.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.jeecg.modules.system.entity.SysDepartManage;
import org.jeecg.modules.system.mapper.SysDepartManageMapper;
import org.jeecg.modules.system.service.ISysDepartManageService;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Map;

/**
 * @Description: 部门角色
 * @Author: jeecg-boot
 * @Date:   2020-02-12
 * @Version: V1.0
 */
@Service
public class SysDepartManageServiceImpl extends ServiceImpl<SysDepartManageMapper, SysDepartManage> implements ISysDepartManageService {

    @Override
    public List<SysDepartManage> findMenu(String parentID) {
        QueryWrapper queryWrapper = new QueryWrapper<>();
        //查询条件
        queryWrapper.eq("parent_id", parentID);
        List<SysDepartManage> list = baseMapper.selectList(queryWrapper);
        for (SysDepartManage departManage : list) {
            //递归子类数据
            departManage.setChildMenu(findMenu(departManage.getResourceId().toString()));
        }
        return list;
    }
}

package org.jeecg.modules.system.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.jeecg.modules.system.entity.SysDepartManage;
import org.jeecg.modules.system.mapper.SysDepartManageMapper;
import org.jeecg.modules.system.service.ISysDepartManageService;
import org.springframework.stereotype.Service;

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


@Service
public class SysDepartManageServiceImpl extends ServiceImpl<SysDepartManageMapper, SysDepartManage> implements ISysDepartManageService {


    @Override
    public List<SysDepartManage> findMenu(String parentID) {
        //数据查询
        List<SysDepartManage> list = baseMapper.selectList(new QueryWrapper());
        //新建一个用于接收数据的list
        List<SysDepartManage> resultList = new ArrayList<>();
        for (SysDepartManage result : list) {
            if (result.getParentId() == 0) {
                //调用方法给子类添加数据
                resultList.add(getMenuTree(result, list));
            }
        }
        return resultList;
    }

    private SysDepartManage getMenuTree(SysDepartManage result, List<SysDepartManage> list) {
        for (SysDepartManage sysDepartManage : list) {
            //如果父类主键等于传过来实体类的ID
            if (sysDepartManage.getParentId().equals(result.getResourceId())) {
                if (result.getChildMenu() == null) {
                    result.setChildMenu(new ArrayList<>());
                }
                // 递归调用
                result.getChildMenu().add(getMenuTree(sysDepartManage, list));
            }
        }
        return result;
    }

}

package org.jeecg.modules.system.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import org.jeecg.modules.system.entity.SysDepartManage;
import java.util.List;
import java.util.Map;


public interface SysDepartManageMapper extends BaseMapper<SysDepartManage> {
    
}