购物车常见实现方式

1、实现方式⼀:存储到数据库性能存在瓶颈
2、实现方式⼆:前端本地存储-localstoragesessionstoragelocalstorage在浏览器中存储key/value 对，没有过期时间。sessionstorage在浏览器中存储 key/value 对,在关闭会话窗⼝后将会删除这些数据。
3、实现方式三:后端存储到缓存如redis可以开启AOF持久化防⽌重启丢失(推荐)

购物⻋数据结构介绍

⼀个购物车里面，存在多个购物项，所以购物车结构是⼀个双层Map：
Map<String,Map<String,String>>
第⼀层Map，Key是⽤户id
第⼆层Map，Key是购物⻋中商品id，值是购物⻋数据

相关VO类和数据准备

VideoDO

@Data
@NoArgsConstructor
@AllArgsConstructor
public class VideoDO {private int id;private String title;private String img;private int price;

CartItemVO

public class CartItemVO {/*** 商品id*/private Integer productId;/*** 购买数量*/private Integer buyNum;/*** 商品标题*/private String productTitle;/*** 图片*/private String productImg;/*** 商品单价*/private int price;/*** 总价格，单价+数量*/private int totalPrice;public int getProductId() {return productId;}public void setProductId(int productId) {this.productId = productId;}public Integer getBuyNum() {return buyNum;}public void setBuyNum(Integer buyNum) {this.buyNum = buyNum;}public String getProductTitle() {return productTitle;}public void setProductTitle(String productTitle) {this.productTitle = productTitle;}public String getProductImg() {return productImg;}public void setProductImg(String productImg) {this.productImg = productImg;}/*** 商品单价 * 购买数量** @return*/public int getTotalPrice() {return this.price * this.buyNum;}public int getPrice() {return price;}public void setPrice(int price) {this.price = price;}public void setTotalPrice(int totalPrice) {this.totalPrice = totalPrice;}
}

CartVO

import java.util.List;public class CartVO {/*** 购物项*/private List<CartItemVO> cartItems;/*** 购物车总价格*/private Integer totalAmount;/*** 总价格* @return*/public int getTotalAmount() {return cartItems.stream().mapToInt(CartItemVO::getTotalPrice).sum();}public List<CartItemVO> getCartItems() {return cartItems;}public void setCartItems(List<CartItemVO> cartItems) {this.cartItems = cartItems;}
}

数据源层

import net.xdclass.xdclassredis.model.VideoDO;
import org.springframework.stereotype.Repository;import java.util.HashMap;
import java.util.Map;@Repository
public class VideoDao {private static Map<Integer,VideoDO> map = new HashMap<>();static {map.put(1, new VideoDO(1,"工业级PaaS云平台+SpringCloudAlibaba 综合项目实战(完结)","https://xdclass.net",1099));map.put(2,new VideoDO(2,"玩转新版高性能RabbitMQ容器化分布式集群实战","https://xdclass.net",79));map.put(3,new VideoDO(3,"新版后端提效神器MybatisPlus+SwaggerUI3.X+Lombok","https://xdclass.net",49));map.put(4,new VideoDO(4,"玩转Nginx分布式架构实战教程 零基础到高级","https://xdclass.net",49));map.put(5,new VideoDO(5,"ssm新版SpringBoot2.3/spring5/mybatis3","https://xdclass.net",49));map.put(6,new VideoDO(6,"新一代微服务全家桶AlibabaCloud+SpringCloud实战","https://xdclass.net",59));}/*** 模拟从数据库找* @param videoId* @return*/public VideoDO findDetailById(int videoId) {return map.get(videoId);}
}

json⼯具类

import com.fasterxml.jackson.databind.ObjectMapper;public class JsonUtil {private static final ObjectMapper MAPPER = new ObjectMapper();/*** 把对象转字符串* @param data* @return*/public static String objectToJson(Object data){try {return MAPPER.writeValueAsString(data);}catch (Exception e){e.printStackTrace();}return null;}/*** json字符串转对象* @param jsonData* @param beanType* @param <T>* @return*/public static <T> T jsonToPojo(String jsonData, Class<T> beanType){try {T t = MAPPER.readValue(jsonData,beanType);return t;}catch (Exception e){e.printStackTrace();}return null;}}

添加购物车接口、查看我的购物车、清空购物车

import net.xdclass.xdclassredis.dao.VideoDao;
import net.xdclass.xdclassredis.model.VideoDO;
import net.xdclass.xdclassredis.util.JsonData;
import net.xdclass.xdclassredis.util.JsonUtil;
import net.xdclass.xdclassredis.vo.CartItemVO;
import net.xdclass.xdclassredis.vo.CartVO;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.BoundHashOperations;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.ArrayList;
import java.util.List;@RestController
@RequestMapping("api/v1/cart")
public class CartController {@Autowiredprivate RedisTemplate redisTemplate;@Autowiredprivate VideoDao videoDao;@RequestMapping("add")public JsonData addCart(int videoId,int buyNum){//获取购物车BoundHashOperations<String,Object,Object> myCart = getMyCartOps();Object cacheObj = myCart.get(videoId+"");String result = "";if(cacheObj!=null){result = (String)cacheObj;}//购物车没这个商品if(cacheObj == null){CartItemVO cartItem = new CartItemVO();VideoDO videoDO = videoDao.findDetailById(videoId);cartItem.setBuyNum(buyNum);cartItem.setPrice(videoDO.getPrice());cartItem.setProductId(videoDO.getId());cartItem.setProductImg(videoDO.getImg());cartItem.setProductTitle(videoDO.getTitle());myCart.put(videoId+"",JsonUtil.objectToJson(cartItem));}else {//增加商品购买数量CartItemVO cartItemVO = JsonUtil.jsonToPojo(result,CartItemVO.class);cartItemVO.setBuyNum(cartItemVO.getBuyNum()+buyNum);myCart.put(videoId+"",JsonUtil.objectToJson(cartItemVO));}return JsonData.buildSuccess();}/*** 查看我的购物车*/@RequestMapping("mycart")public JsonData getMycart(){//获取购物车BoundHashOperations<String,Object,Object> myCart = getMyCartOps();List<Object> itemList =  myCart.values();List<CartItemVO> cartItemVOList = new ArrayList<>();for(Object item : itemList){CartItemVO cartItemVO = JsonUtil.jsonToPojo((String)item,CartItemVO.class);cartItemVOList.add(cartItemVO);}CartVO cartVO = new CartVO();cartVO.setCartItems(cartItemVOList);return JsonData.buildSuccess(cartVO);}/*** 清空我的购物车* @return*/@RequestMapping("clear")public JsonData clear(){String key = getCartKey();redisTemplate.delete(key);return JsonData.buildSuccess();}/*** 抽取我的购物车通用方法* @return*/private BoundHashOperations<String,Object,Object> getMyCartOps(){String key = getCartKey();return redisTemplate.boundHashOps(key);}private String getCartKey(){//用户的id,从拦截器获取int userId = 88;String cartKey = String.format("video:cart:%s",userId);return cartKey;}}