一、本主的应用场景

    部门里面有一个属性是当前部门的上级部门，而当前部门又会有下级部门，下级部门还有下级部门，这就形成了一个向下无限循环，呈现出树状结构。

二、认识JSONObject

    JSONObject只是一种数据结构，可以理解为JSON格式的数据结构（key-value 结构），可以使用put方法给json对象添加元素。JSONObject可以很方便的转换成字符串，也可以很方便的把其他对象转换成JSONObject对象。

postman测试效果图

 

 建表（主键id自增长）

 

 Entity实体类

package com.example.unicom.entity;import lombok.Data;import java.util.ArrayList;
import java.util.List;@Data
public class RoleTree {private Integer id;private String role_name;private Integer parent_role_id;private List<RoleTree>trees =new ArrayList<>();
}

        Controller （GeneralResponse为自己添加的公共返回实体类，正式开发加，做练习可以不加）

package com.example.unicom.controller;import com.example.unicom.entity.RoleTree;
import com.example.unicom.entity.base.GeneralResponse;
import com.example.unicom.service.RoleTreeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;import java.util.List;
/*** @author 孙翊轩* @since 2021-09-02*/
@RestController
@RequestMapping("/isp/unicom/roletree")
public class RoleTreeController {@Autowiredprivate RoleTreeService roleTreeService;@RequestMapping(value ="selectRoleTree",method = RequestMethod.GET)public GeneralResponse selectRoleTree(){try{List<RoleTree> roleTreeList=roleTreeService.selectRoleTree();return new GeneralResponse("SUCCESS","查询成功",roleTreeList);}catch (Exception e){e.printStackTrace();}return new GeneralResponse("FAIL","查询失败",null);}
}

Service接口 

package com.example.unicom.mapper;import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.unicom.entity.RoleTree;
import org.springframework.stereotype.Repository;import java.util.List;@Repository
public interface RoleTreeMapper extends BaseMapper<RoleTree> {List<RoleTree> selectRoleTree();
}

 @Service 业务层

package com.example.unicom.service.impl;import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.example.unicom.entity.RoleTree;
import com.example.unicom.entity.UserRole;
import com.example.unicom.mapper.RoleTreeMapper;
import com.example.unicom.mapper.UserRoleMapper;
import com.example.unicom.service.RoleTreeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.util.ArrayList;
import java.util.List;@Service
public class RoleTreeServiceImpl extends ServiceImpl<RoleTreeMapper,RoleTree>implements RoleTreeService{@Autowiredprivate RoleTreeMapper roleTreeMapper;@Autowiredprivate UserRoleMapper userRoleMapper;/*** 获取所有分类* @return*/@Overridepublic List<RoleTree> selectRoleTree() {List<RoleTree>roleTreeList=roleTreeMapper.selectRoleTree();List<UserRole>userRoleList=userRoleMapper.selectAll();//定义一个新的ListList<RoleTree>treeList=new ArrayList<>();//找到所有的一级分类for(RoleTree roleTree :roleTreeList){//一级菜单的parent_role_id是0if(roleTree.getParent_role_id()==0){treeList.add(roleTree);}}//为1级菜单设置子菜单for (RoleTree roleTree :treeList){roleTree.setTrees(getchilde(roleTree.getId(),roleTreeList));}return treeList;}/*** 递归查找子菜单* @param id 当前菜单id* @param rootList 要查找的列表*/private List<RoleTree>getchilde(Integer id,List<RoleTree>rootList){//子菜单的子菜单List<RoleTree>childList =new ArrayList<>();for (RoleTree roleTree :rootList){//遍历所有节点，将父菜单id与传过来的id比较if(roleTree.getParent_role_id().equals(id)){childList.add(roleTree);}}//将子菜单的子菜单再做循环for(RoleTree roleTree :childList){roleTree.setTrees(getchilde(roleTree.getId(),rootList));}//退出递归if (childList.size()==0){return null;}return childList;}
}

Mapper接口  

package com.example.unicom.service;import com.baomidou.mybatisplus.extension.service.IService;
import com.example.unicom.entity.RoleTree;import java.util.List;public interface RoleTreeService extends IService<RoleTree> {List<RoleTree> selectRoleTree();
}

Mapper .xml 映射 

 

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.unicom.mapper.UserRoleMapper"><select id="selectRoleTree" parameterType="com.example.unicom.entity.UserRole" resultType="com.example.unicom.entity.UserRole">SELECT user_role.user_id,user_role.user_name,user_role.jg_nameFROM user_role</select>
</mapper>