【苍穹外卖】Day 7 缓存、购物车相关接口

1 缓存

存在问题：

用户端小程序展示的菜品数据都是通过査询数据库获得，如果用户端访问量比较大，数据库访问压力随之增大

=>解决：

通过 Redis 来缓存菜品数据，减少数据库查询操作

缓存逻辑分析：

每个分类下的菜品保存一份缓存数据
数据库中菜品数据有变更时清理缓存数据

浏览菜品页面使用的路径：

GET /user/dish/list?categoryId=1

在 redis 这样保存

package com.sky.controller.user;import com.sky.constant.StatusConstant;
import com.sky.entity.Dish;
import com.sky.result.Result;
import com.sky.service.DishService;
import com.sky.vo.DishVO;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
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;@RestController("userDishController")
@RequestMapping("/user/dish")
@Slf4j
@Api(tags = "C端-菜品浏览接口")
public class DishController {@Autowiredprivate DishService dishService;@Autowiredprivate RedisTemplate redisTemplate;/*** 根据分类id查询菜品** @param categoryId* @return*/@GetMapping("/list")@ApiOperation("根据分类id查询菜品")public Result<List<DishVO>> list(Long categoryId) {// 1.查询 redis 中是否有菜品数据//构造 keyString key = "dish_" + categoryId.toString();List<DishVO> list = (List<DishVO>) redisTemplate.opsForValue().get(key);if (list != null && list.size() > 0) {// 2.如果有，直接返回return Result.success(list);}// 3.如果没有，先去数据库查询，然后数据缓存在 redis，返回Dish dish = new Dish();dish.setCategoryId(categoryId);dish.setStatus(StatusConstant.ENABLE);//查询起售中的菜品list = dishService.listWithFlavor(dish);//缓存redisredisTemplate.opsForValue().set(key, list);return Result.success(list);}}

清理缓存

当修改完菜品信息时，修改了sql数据库，但再去浏览菜品，访问的是 redis，需要 清理缓存

然后在增删改操作return前，加上

cleanCache("dish_*");

2 Spring Cache

Spring Cache 提供了一层抽象，底层可以切换不同的缓存实观，例如：

EHCache
Caffeine
Redis

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-cache</artifactId><version>2.7.3</version>
</dependency>

/*** 新增菜品，不光加入 菜品表 dish 还有 口味表 dish flavor** @param dishDTO* @return*/@PostMapping@ApiOperation("新增菜品")@CacheEvict(cacheNames = "dishCache",key = "#dishDTO.categoryId")public Result add(@RequestBody DishDTO dishDTO) {log.info("新增菜品");dishService.add(dishDTO);return Result.success();}

如果不好获得categoryId，就全删除

@CacheEvict(cacheNames = "dishCache",allEntries = true)

/*** 根据菜品 id 删除菜品** @param ids* @return*/@DeleteMapping@ApiOperation("根据菜品 id 删除菜品")@CacheEvict(cacheNames = "dishCache",allEntries = true)public Result deleteById(@RequestParam List<Long> ids) {dishService.delete(ids);return Result.success();}

为什么不是 key = "#{dishDTO.categoryId}"：

# 用于在Spring缓存注解中的SpEL表达式，表示引用方法参数
#{} 用于解析Spring上下文中的Bean或者系统属性

3 缓存套餐

【增删改】要【删除缓存】---> @CacheEvict

【查】要【访问缓存】---> @Cacheable

对于用户端：

只能查询，不能增删改，所以只加 @Cacheable

对于管理端：

/*** 新增套餐** @param setmealDTO* @return*/@PostMapping@ApiOperation("新增套餐")@CacheEvict(cacheNames = "setmealCache",key = "#setmealDTO.categoryId")public Result add(@RequestBody SetmealDTO setmealDTO) {setmealService.add(setmealDTO);return Result.success();}

4 添加购物车

4.1 设计

设计冗余字段：用空间换时间

4.2 实现

controller

service

package com.sky.service.impl;import com.sky.context.BaseContext;
import com.sky.dto.ShoppingCartDTO;
import com.sky.entity.Dish;
import com.sky.entity.Setmeal;
import com.sky.entity.ShoppingCart;
import com.sky.mapper.DishMapper;
import com.sky.mapper.SetmealMapper;
import com.sky.mapper.ShoppingCartMapper;
import com.sky.service.ShoppingCartService;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.time.LocalDateTime;
import java.util.List;@Service
public class ShoppingCartServiceImpl implements ShoppingCartService {@Autowiredprivate ShoppingCartMapper shoppingCartMapper;@Autowiredprivate DishMapper dishMapper;@Autowiredprivate SetmealMapper setmealMapper;/*** 添加购物车** @param shoppingCartDTO*/public void add(ShoppingCartDTO shoppingCartDTO) {//判断当前商品是否购物车中已存在ShoppingCart shoppingCart = new ShoppingCart();BeanUtils.copyProperties(shoppingCartDTO, shoppingCart);Long userId = BaseContext.getCurrentId();shoppingCart.setUserId(userId);List<ShoppingCart> list = shoppingCartMapper.list(shoppingCart);if (list != null && list.size() > 0) {//如果存在，数量加一ShoppingCart cart = list.get(0); // 直接取出唯一的一条数据cart.setNumber(cart.getNumber() + 1);shoppingCartMapper.updateNumberById(cart);} else {//如果不存在，插入数据//首先构造一个 ShoppingCart 对象//再补充数据：//name image amount create_timeLong dishId = shoppingCart.getDishId();Long setmealId = shoppingCart.getSetmealId();if (dishId != null) {// 查询菜品表获取 name image amountDish dish = dishMapper.getById(dishId);shoppingCart.setName(dish.getName());shoppingCart.setImage(dish.getImage());shoppingCart.setAmount(dish.getPrice());shoppingCart.setNumber(1); // 注意要设置数量为 1} else {// 查询套餐表获取 name image amountSetmeal setmeal = setmealMapper.getById(setmealId);shoppingCart.setName(setmeal.getName());shoppingCart.setImage(setmeal.getImage());shoppingCart.setAmount(setmeal.getPrice());shoppingCart.setNumber(1); // 注意要设置数量为 1}shoppingCart.setCreateTime(LocalDateTime.now());}shoppingCartMapper.insert(shoppingCart);}
}

mapper

package com.sky.mapper;import com.sky.entity.ShoppingCart;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Update;import java.util.List;@Mapper
public interface ShoppingCartMapper {/*** 条件查询购物车** @param shoppingCartDTO* @return*/List<ShoppingCart> list(ShoppingCart shoppingCartDTO);/*** 根据id更新菜品数量number（加一）** @param cart*/@Update("update sky_take_out.shopping_cart set number = #{number} where id = #{id}")void updateNumberById(ShoppingCart cart);/*** 加入购物车* @param shoppingCart*/@Insert("insert into sky_take_out.shopping_cart" +"(name, image, user_id, dish_id, setmeal_id, dish_flavor, amount, create_time)" +"values" +"(#{name},#{image},#{userId},#{dishId},#{setmealId},#{dishFlavor},#{amount},#{createTime})")void insert(ShoppingCart shoppingCart);
}

xml

<select id="list" resultType="com.sky.entity.ShoppingCart">select *from sky_take_out.shopping_cart<where><if test="userId != null">and user_id = #{userId}</if><if test="dishId != null">and dish_id = #{dishId}</if><if test="setmealId != null">and setmeal_id = #{setmealId}</if><if test="dishFlavor != null">and dish_flavor = #{dishFlavor}</if></where>
</select>

4.3 测试

5 查看购物车与清空购物车

查看

Path：/user/shoppingCart/list

Method：GET

清空

Path：/user/shoppingCart/clean

Method：DELETE

controller

/*** 查看购物车** @return*/@ApiOperation("查看购物车")@GetMapping("/list")public Result<List<ShoppingCart>> list() {List<ShoppingCart> list = shoppingCartService.list();return Result.success(list);}/*** 清空购物车** @return*/@ApiOperation("清空购物车")@DeleteMapping("/clean")public Result clean() {shoppingCartService.clean();return Result.success();}

service

    /*** 查看购物车*/@Overridepublic List<ShoppingCart> list() {List<ShoppingCart> list = shoppingCartMapper.listAll();return list;}/*** 清空购物车*/@Overridepublic void clean() {shoppingCartMapper.clean();}

mapper

/*** 查看购物车，返回所有数据** @return*/@Select("select * from sky_take_out.shopping_cart")List<ShoppingCart> listAll();/*** 清空购物车*/@Delete("delete from sky_take_out.shopping_cart")void clean();

测试