Stream流递归查询部门树

Java 递归查询树是很常见的功能，也有很多写法，小编这里记录stream流递归部门树写法，自从小编用上stream流之后，是爱不释手，的确是个不错的好东西，话不多说，直接上代码

第一步：先创建dept部门表，简单塞点数据
在这里插入图片描述
第二步：创建实体类

package com.example.work.entity;import lombok.Data;@Data
public class Dept {/*** 主键id*/private Integer id;/*** 部门名称*/private String deptName;/*** 父级id*/private Integer parentId;
}

第三步：创建部门vo对象

package com.example.work.vo;import com.example.work.entity.Dept;
import lombok.Data;import java.util.List;/*** @Description: 部门树vo* @Author: lyz* @CreateTime: 2024-01-11*/
@Data
public class DeptTreeVO extends Dept {private List<DeptTreeVO> childrenList;
}

第三步：编写controller层

package com.example.work.controller;import com.baomidou.mybatisplus.extension.api.R;
import com.example.work.service.DeptService;
import com.example.work.vo.DeptTreeVO;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.List;/*** @Description: TODO* @Author: lyz* @CreateTime: 2024-01-11*/
@RestController
@RequestMapping("dept")
public class DeptController {@AutowiredDeptService deptService;/*** @Description: 部门树* @return R**/@GetMapping("/getTreeList")public R getTreeList(){List<DeptTreeVO> treeVOList = deptService.getTreeList();return R.ok(treeVOList);}
}

第四步：业务层代码逻辑实现

package com.example.work.service.impl;import com.baomidou.mybatisplus.core.toolkit.ObjectUtils;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.example.work.dao.DeptMapper;
import com.example.work.entity.Dept;
import com.example.work.service.DeptService;
import com.example.work.vo.DeptTreeVO;
import org.springframework.beans.BeanUtils;
import org.springframework.stereotype.Service;import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;/*** @Description: TODO* @Author: lyz* @CreateTime: 2024-01-11*/
@Service
public class DeptServiceImpl extends ServiceImpl<DeptMapper, Dept> implements DeptService {@Overridepublic List<DeptTreeVO> getTreeList() {List<DeptTreeVO> deptTreeVOList = new ArrayList<>();List<Dept> list = this.list();list.forEach(dept -> {DeptTreeVO deptTreeVO = new DeptTreeVO();BeanUtils.copyProperties(dept, deptTreeVO);deptTreeVOList.add(deptTreeVO);});//获取父部门信息List<DeptTreeVO> deptTreeVOS = deptTreeVOList.stream().filter(x -> x.getParentId() == 0).map(deptTreeVO -> {deptTreeVO.setChildrenList(getChildrenList(deptTreeVO, deptTreeVOList));return deptTreeVO;}).collect(Collectors.toList());return deptTreeVOS;}/*** @return List<DeptTreeVO> 子部门信息* @Description: 递归查询子部门* @param[1] root 父部门* @param[2] deptTreeVOList 所有部门**/private List<DeptTreeVO> getChildrenList(DeptTreeVO root, List<DeptTreeVO> deptTreeVOList) {List<DeptTreeVO> childrenList = deptTreeVOList.stream().filter(x -> {return Objects.equals(x.getParentId(), root.getId());}).map(deptTreeVO -> {deptTreeVO.setChildrenList(getChildrenList(deptTreeVO, deptTreeVOList));return deptTreeVO;}).collect(Collectors.toList());return childrenList;}
}