1、新建实体类

package com.example.springboot3.entity;import lombok.Builder;
import lombok.Data;import java.util.List;@Data
@Builder
public class Menu {/*** id*/public Integer id;/*** 名称*/public String name;/*** 父id ，根节点为0*/public Integer parentId;/*** 子节点信息*/public List<Menu> children;public Menu(Integer id, String name, Integer parentId) {this.id = id;this.name = name;this.parentId = parentId;}public Menu(Integer id, String name, Integer parentId, List<Menu> children) {this.id = id;this.name = name;this.parentId = parentId;this.children = children;}
}

2、controller测试，正式环境可到service进行分层

package com.example.springboot3.controller;import com.example.springboot3.entity.Menu;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;@RestController
public class MenuController {@GetMapping("/getMenuTree")public List<Menu> getMenuTree(){//模拟从数据库查询出来List<Menu> menus = Arrays.asList(new Menu(1,"根节点",0),new Menu(2,"子节点1",1),new Menu(3,"子节点1.1",2),new Menu(4,"子节点1.2",2),new Menu(5,"根节点1.3",2),new Menu(6,"根节点2",1),new Menu(7,"根节点2.1",6),new Menu(8,"根节点2.2",6),new Menu(9,"根节点2.2.1",7),new Menu(10,"根节点2.2.2",7),new Menu(11,"根节点3",1),new Menu(12,"根节点3.1",11));//获取父节点List<Menu> collect = menus.stream().filter(m -> m.getParentId() == 0).map((m) -> {m.setChildren(getChildrens(m, menus));return m;}).collect(Collectors.toList());return collect;}private List<Menu> getChildrens(Menu root, List<Menu> all) {List<Menu> children = all.stream().filter(m ->Objects.equals(m.getParentId(), root.getId())).map((m) -> {m.setChildren(getChildrens(m, all));return m;}).collect(Collectors.toList());return children;}}

3、结果