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在开发投诉分类功能模块时#xff0c;遇到过这样一个业务场景#xff1a;后端需要按层级结构返回二级分类菜单所需数据#xff0c;换言之#xff0c;将具有父子关系的List结果集数据转为树状结构数据来返回
二级分类菜单
前期准备
这里简单复刻下真实场景中 出现的…前言
在开发投诉分类功能模块时遇到过这样一个业务场景后端需要按层级结构返回二级分类菜单所需数据换言之将具有父子关系的List结果集数据转为树状结构数据来返回
二级分类菜单
前期准备
这里简单复刻下真实场景中 出现的二级分类菜单层级结构返回
数据库设计
建表语句如下
DROP TABLE IF EXISTS menu;
CREATE TABLE menu (id bigint NOT NULL AUTO_INCREMENT,name varchar(50) CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci NULL DEFAULT NULL COMMENT 名称,parent_id bigint NULL DEFAULT NULL COMMENT 父级id,PRIMARY KEY (id) USING BTREE
) ENGINE InnoDB CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci ROW_FORMAT DYNAMIC;-- ----------------------------
-- Records of menu
-- ----------------------------
INSERT INTO menu VALUES (1, 质量问题, 0);
INSERT INTO menu VALUES (2, 变质, 1);
INSERT INTO menu VALUES (3, 过期, 1);
INSERT INTO menu VALUES (4, 包装破损, 1);
INSERT INTO menu VALUES (5, 服务问题, 0);
INSERT INTO menu VALUES (6, 态度恶劣, 5);
INSERT INTO menu VALUES (7, 东拉西扯, 5); 效果图预览 这里是在SpringBoot项目中演示实现的持久层框架选用MyBatis-Plus版本号3.5.3.1
之所以强调MP版本号是因为之前在实现分页时遇过挫真实项目选用的版本是3.3.2而自己在学习MP时选择版本是3.5.3.1。MP官方文档在不同版本中有关分页插件的使用介绍可能存在不同实际开发中对引入MP依赖的版本号还是要有所关注 开发测试
创建实体类
package com.atguigu.mybatisplus.pojo;import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;/*** author Songguo* date 2023/11/15 9:56*/
Data
TableName(menu)
public class Menu {private Long id;private String name;private Long parentId;
}创建mapper层
package com.atguigu.mybatisplus.mapper;import com.atguigu.mybatisplus.pojo.Menu;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;public interface MenuMapper extends BaseMapperMenu {
}创建service层接口及实现类
package com.atguigu.mybatisplus.service;import com.atguigu.mybatisplus.pojo.Menu;
import com.baomidou.mybatisplus.extension.service.IService;public interface MenuService extends IServiceMenu {
}package com.atguigu.mybatisplus.service.impl;import com.atguigu.mybatisplus.mapper.MenuMapper;
import com.atguigu.mybatisplus.pojo.Menu;
import com.atguigu.mybatisplus.service.MenuService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.springframework.stereotype.Service;/*** author Songguo* date 2023/11/15 10:00*/
Service
public class MenuServiceImpl extends ServiceImplMenuMapper, Menu implements MenuService {
}创建测试类
package com.atguigu.mybatisplus;import com.atguigu.mybatisplus.pojo.Menu;
import com.atguigu.mybatisplus.service.MenuService;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;/*** author Songguo* date 2023/11/15 10:02*/
SpringBootTest
public class MenuServiceImplTest {Autowiredprivate MenuService menuService;Testpublic void ListToTreeTest() {ListMenu list menuService.list();// 存放要返回的树状结构数据ListMapString, Object MenuList new ArrayList();for (Menu menu : list) {if (Long.valueOf(0) menu.getParentId()) {MapString, Object map new HashMap();map.put(id, menu.getId());map.put(name, menu.getName());// map.put(parentId, menu.getParentId());map.put(children, getChildren(list, menu.getId()));MenuList.add(map);}}MenuList.forEach(System.out::println);}public ListMapString, Object getChildren(ListMenu list, Long topId) {ListMapString, Object data new ArrayList();for (Menu menu : list) {if (topId menu.getParentId()) {MapString, Object map new HashMap();map.put(id, menu.getId());map.put(name, menu.getName());// map.put(parentId, menu.getParentId());data.add(map);}}return data;}}注意 在真实场景中并不需要返回每条记录的所有字段值主要看前端需要接收那些数据
实现思路很简单
1️⃣获取分类菜单所有记录
2️⃣遍历找出一级节点父节点然后在调用getChildren()重金寻子方法获取二级节点子节点
3️⃣通过ListMapString,Object来存放结果集
三级分类菜单
前期准备
这里简单复刻下真实场景中 出现的三级分类菜单层级结构返回
数据库设计
建表语句如下
CREATE TABLE address (id INT AUTO_INCREMENT PRIMARY KEY,name VARCHAR(50) NOT NULL,parent_id INT NOT NULL,level INT NOT NULL
);INSERT INTO address (name, parent_id, level) VALUES (湖北, 0, 1);
INSERT INTO address (name, parent_id, level) VALUES (辽宁, 0, 1);
INSERT INTO address (name, parent_id, level) VALUES (武汉, 1, 2);
INSERT INTO address (name, parent_id, level) VALUES (荆州, 1, 2);
INSERT INTO address (name, parent_id, level) VALUES (沈阳, 2, 2);
INSERT INTO address (name, parent_id, level) VALUES (蔡甸区, 3, 3);
INSERT INTO address (name, parent_id, level) VALUES (江夏区, 3, 3);
INSERT INTO address (name, parent_id, level) VALUES (沙市区, 4, 3);
INSERT INTO address (name, parent_id, level) VALUES (大东区, 5, 3);
INSERT INTO address (name, parent_id, level) VALUES (浑南区, 5, 3);效果图预览 开发测试
创建实体类
package com.atguigu.mybatisplus.pojo;import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;/*** author Songguo* date 2023/11/26 17:04*/
Data
TableName(address)
public class Address {private int id;private String name;private int parentId;private int level;
}创建mapper层
package com.atguigu.mybatisplus.mapper;import com.atguigu.mybatisplus.pojo.Address;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;public interface AddressMapper extends BaseMapperAddress {
}创建service层接口及实现类
package com.atguigu.mybatisplus.service;import com.atguigu.mybatisplus.pojo.Address;
import com.baomidou.mybatisplus.extension.service.IService;public interface AddressService extends IServiceAddress {
}package com.atguigu.mybatisplus.service.impl;import com.atguigu.mybatisplus.mapper.AddressMapper;
import com.atguigu.mybatisplus.pojo.Address;
import com.atguigu.mybatisplus.service.AddressService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.springframework.stereotype.Service;/*** author Songguo* date 2023/11/26 17:08*/
Service
public class AddressServiceImpl extends ServiceImplAddressMapper, Address implements AddressService {
}创建测试类
package com.atguigu.mybatisplus;import com.atguigu.mybatisplus.pojo.Address;
import com.atguigu.mybatisplus.service.AddressService;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;/*** author Songguo* date 2023/11/26 17:10*/
SpringBootTest
public class AddressServiceImplTest {Autowiredprivate AddressService addressService;Testpublic void getAddress() {ListAddress list addressService.list();// list.forEach(System.out::println);// 存放结果集ListMapString, Object addressList new ArrayList();for (Address address : list) {if (address.getLevel() 1) {MapString, Object map new HashMap();map.put(id, address.getId());map.put(name, address.getName());// map.put(parentId, address.getParentId());map.put(children, getChildren(list, address.getId()));addressList.add(map);}}addressList.forEach(System.out::println);}public ListMapString, Object getChildren(ListAddress list, int parentId) {ListMapString, Object data new ArrayList();for (Address address : list) {HashMapString, Object map new HashMap();if (parentId address.getParentId()) {map.put(id, address.getId());map.put(name, address.getName());// map.put(parentId, address.getParentId());if (address.getLevel() 3) {map.put(children, getChildren(list, address.getId()));}data.add(map);}}return data;}}小结
二级分类菜单的层级结构返回是在真实项目中遇到的而三级分类菜单的层级结构返回是模拟真实场景下的需求进行扩展实现的
弄懂了二级分类和三级分类多级分类还会远嘛
