package com.u.api.service.impl; import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper; import com.baomidou.mybatisplus.core.conditions.update.UpdateWrapper; import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl; import com.u.api.mapper.GoodsMapper; import com.u.api.mapper.ShopingCartMapper; import com.u.api.model.ShopingCart; import com.u.api.service.ShopingCartService; import org.springframework.stereotype.Service; import javax.annotation.Resource; import java.util.List; @Service public class ShopingCartServiceImpl extends ServiceImpl<ShopingCartMapper, ShopingCart> implements ShopingCartService { @Resource private ShopingCartMapper shopingCartMapper; @Resource private GoodsMapper goodsMapper; @Override public int add(ShopingCart shopingCart) { QueryWrapper<ShopingCart> qw = new QueryWrapper<>(); qw.eq("gid",shopingCart.getGid()); qw.eq("uid",shopingCart.getUid()); ShopingCart shopingCart1 = shopingCartMapper.selectOne(qw); int rs = 0; if(shopingCart1 == null){ shopingCart.setNum(1); rs = shopingCartMapper.insert(shopingCart); }else { UpdateWrapper<ShopingCart> updateWrapper = new UpdateWrapper(); updateWrapper.eq("uid",shopingCart.getUid()); updateWrapper.eq("gid",shopingCart.getGid()); updateWrapper.setSql("num = num + 1"); rs = shopingCartMapper.update(null,updateWrapper); } return rs; } @Override public int del(ShopingCart shopingCart) { QueryWrapper<ShopingCart> queryWrapper = new QueryWrapper<>(); queryWrapper.eq("uid",shopingCart.getUid()); queryWrapper.eq("id",shopingCart.getId()); return shopingCartMapper.delete(queryWrapper); } @Override public List<ShopingCart> getShopingCart(String account) { QueryWrapper<ShopingCart> queryWrapper = new QueryWrapper<>(); queryWrapper.eq("uid",account); List<ShopingCart> shopingCarts = shopingCartMapper.selectList(queryWrapper); return shopingCarts; } }

这是一个基于SpringBoot框架开发的购物车服务实现类，下面对代码进行逐行注释：

package com.u.api.service.impl;  
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper; 
import com.baomidou.mybatisplus.core.conditions.update.UpdateWrapper; 
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl; 
import com.u.api.mapper.GoodsMapper; 
import com.u.api.mapper.ShopingCartMapper; 
import com.u.api.model.ShopingCart; 
import com.u.api.service.ShopingCartService; 
import org.springframework.stereotype.Service;  
import javax.annotation.Resource; 
import java.util.List; 

@Service 
public class ShopingCartServiceImpl extends ServiceImpl<ShopingCartMapper, ShopingCart> implements ShopingCartService {     
    @Resource     
    private ShopingCartMapper shopingCartMapper;     
    @Resource     
    private GoodsMapper goodsMapper;

    // 添加商品到购物车
    @Override     
    public int add(ShopingCart shopingCart) {         
        QueryWrapper<ShopingCart> qw = new QueryWrapper<>();
        qw.eq("gid",shopingCart.getGid());   // 根据商品id查询购物车中是否有该商品
        qw.eq("uid",shopingCart.getUid());   // 根据用户id查询购物车中是否有该用户
        ShopingCart shopingCart1 = shopingCartMapper.selectOne(qw); // 查询购物车中是否已经存在该商品
        int rs = 0;         
        if(shopingCart1 == null){   // 如果不存在该商品，则添加一条新纪录
            shopingCart.setNum(1);  // 设置商品数量为1
            rs = shopingCartMapper.insert(shopingCart);  // 将商品添加到购物车，并返回添加结果
        }else {   // 如果已存在该商品，则更新商品数量
            UpdateWrapper<ShopingCart> updateWrapper = new UpdateWrapper();
            updateWrapper.eq("uid",shopingCart.getUid());  // 根据用户id更新商品数量
            updateWrapper.eq("gid",shopingCart.getGid());  // 根据商品id更新商品数量
            updateWrapper.setSql("num = num + 1");   // 商品数量加1
            rs = shopingCartMapper.update(null,updateWrapper);  // 更新商品数量，并返回更新结果
        }         
        return rs;  // 返回添加或更新结果
    }

    // 从购物车中删除商品
    @Override     
    public int del(ShopingCart shopingCart) {         
        QueryWrapper<ShopingCart> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("uid",shopingCart.getUid());  // 根据用户id查询购物车中是否有该用户
        queryWrapper.eq("id",shopingCart.getId());  // 根据购物车id查询要删除的商品
        return shopingCartMapper.delete(queryWrapper);  // 删除购物车中的商品
    }

    // 根据用户id获取购物车中的所有商品
    @Override     
    public List<ShopingCart> getShopingCart(String account) {         
        QueryWrapper<ShopingCart> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("uid",account);  // 根据用户id查询购物车中的商品
        List<ShopingCart> shopingCarts = shopingCartMapper.selectList(queryWrapper);  // 获取购物车中的商品列表
        return shopingCarts;  // 返回购物车中的所有商品
    } 
}

总体来说，这段代码实现了购物车服务的增、删、查等操作。其中，add方法实现了将商品添加到购物车中的功能；del方法实现了从购物车中删除商品的功能；getShopingCart方法实现了根据用户id获取购物车中的所有商品的功能。