一.用户登录添加商品使用cookie存入购物车，并把购物车商品传入到后台

步骤1：创建购物车BO对象

public class ShopcartBO {
    private String itemId;
    private String itemImgUrl;
    private String itemName;
    private String specId;
    private String specName;
    private Integer buyCounts;
    private String priceDiscount;
    private String priceNormal;
    //TODO get和set方法
}

步骤2：创建controller接口购物车数据

@Api(value = "购物车接口controller", tags = {"购物车接口相关的api"})
@RequestMapping("shopcart")
@RestController
public class ShopCatController {
    @ApiOperation(value = "添加商品到购物车", notes = "添加商品到购物车", httpMethod = "POST")
    @PostMapping("/add")
    public JSONResult add(@RequestParam String userId, @RequestBody ShopcartBO shopcartBO, HttpServletRequest request, HttpServletResponse response) {
        //判断用户id是否为空
        if (StringUtils.isBlank(userId)) {return JSONResult.errorMsg("");}
        System.out.println(shopcartBO);
        
        // TODO 前端用户在登录的情况下，添加商品到购物车，会同时在后端同步购物车到redis缓存
        return JSONResult.ok();
    }
}

二.根据用户购物车商品请求后台获取最新商品的价格到购物车页面
步骤1：创建购物车VO信息

public class ShopcartVO {
    private String itemId;
    private String itemImgUrl;
    private String itemName;
    private String specId;
    private String specName;
    private String priceDiscount;
    private String priceNormal;;
}

步骤2：对应mapper.xml中根据商品规格查询对应购物车VO信息

<select id="queryItemsBySpecIds" parameterType="List" resultType="com.imooc.pojo.vo.ShopcartVO">
        SELECT
            t_items.id as itemId,
            t_items.item_name as itemName,
            t_items_img.url as itemImgUrl,
            t_items_spec.id as specId,
            t_items_spec.`name` as specName,
            t_items_spec.price_discount as priceDiscount,
            t_items_spec.price_normal as priceNormal
        FROM
            items_spec t_items_spec
        LEFT JOIN
            items t_items
        ON
            t_items.id = t_items_spec.item_id
        LEFT JOIN
            items_img t_items_img
        on
            t_items_img.item_id = t_items.id
        WHERE
            t_items_img.is_main = 1
        AND
            t_items_spec.id IN
            <foreach collection="paramsList" index="index" item="specId" open="(" separator="," close=")">
              #{specId}
            </foreach>
</select>

步骤3：写mapper对应接口方法

public List queryItemsBySpecIds(@Param(“paramsList”) List specIdsList);

步骤4：创建service接口和实现类

/**
 * 根据规格ids查询最新的购物车中商品数据（用于刷新渲染购物车中的商品数据）
 * @param specIds
 * @return
 */
public List<ShopcartVO> queryItemsBySpecIds(String specIds);

@Transactional(propagation = Propagation.SUPPORTS)
@Override
public List<ShopcartVO> queryItemsBySpecIds(String specIds) {

    String ids[] = specIds.split(",");
    List<String> specIdsList = new ArrayList<>();
    Collections.addAll(specIdsList, ids);

    return itemsMapperCustom.queryItemsBySpecIds(specIdsList);
}

步骤5：编写controller控制访问层

   // 用于用户长时间未登录网站，刷新购物车中的数据（主要是商品价格）
    @ApiOperation(value = "根据商品规格ids查找最新的商品数据", notes = "根据商品规格ids查找最新的商品数据", httpMethod = "GET")
    @GetMapping("/refresh")
    public JSONResult refresh(
            @ApiParam(name = "itemSpecIds", value = "拼接的规格ids", required = true, example = "1001,1003,1005")
            @RequestParam String itemSpecIds) {

        if (StringUtils.isBlank(itemSpecIds)) {
            return JSONResult.ok();
        }

        List<ShopcartVO> list = itemService.queryItemsBySpecIds(itemSpecIds);

        return JSONResult.ok(list);
    }