package com.jt.cart.controller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import com.jt.cart.service.CartService;
import com.jt.common.po.Cart;
import com.jt.common.vo.SysResult;

@Controller
@RequestMapping("/cart")
public class CartController {
    @Autowired
    private CartService cartService;
    //根据用户id查询购物车信息
    @RequestMapping("/query/{userId}")
    @ResponseBody
    public SysResult findCartByUserId(@PathVariable Long userId){
        try {
            List<Cart> cartList=cartService.findCartByUserId(userId);
            return SysResult.oK(cartList);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return SysResult.build(201, "购物车信息查询失败");
    }
    @RequestMapping("/save")
    //实现购物车入库
    public SysResult saveCart(Cart cart){
        try {
            cartService.saveCart(cart);
            return SysResult.oK();
        } catch (Exception e) {
            // TODO: handle exception
        }
        return SysResult.build(201, "购物车新增失败");
    }
}

package com.jt.cart.service;

import java.util.List;

import com.jt.common.po.Cart;

public interface CartService {

    List<Cart> findCartByUserId(Long userId);

    void saveCart(Cart cart);

}

package com.jt.cart.service;

import java.util.Date;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.jt.cart.mapper.CartMapper;
import com.jt.common.po.Cart;
@Service
public class CartServiceImpl implements CartService {
    @Autowired
    private CartMapper cartMapper;

    @Override
    public List<Cart> findCartByUserId(Long userId) {
        Cart cart=new Cart();
        cart.setUserId(userId);
        return cartMapper.select(cart);
    }

    /**
     * 根据userId和itemId判断数据库中是否有该购物车信息
     * 有
     *   数据库num+新num做更新操作
     * 没有数据
     *  应该插入数据库
     */
    /* (non-Javadoc)
     * @see com.jt.cart.service.CartService#saveCart(com.jt.common.po.Cart)
     */
    @Override
    public void saveCart(Cart cart) {       
        Cart cartDB=cartMapper.findCartByUI(cart);
        if(cartDB==null){
            System.out.println("insert cart");
            cart.setCreated(new Date());
            cart.setUpdated(cart.getCreated());
            cartMapper.insert(cart);
        }else{
            System.out.println("insert cart2");
            int num=cartDB.getNum()+cart.getNum();
            cartDB.setNum(num);
            cartDB.setUpdated(new Date());
            cartMapper.updateByPrimaryKeySelective(cartDB);
        }
    }
}

package com.jt.cart.mapper;

import org.apache.ibatis.annotations.Select;

import com.jt.common.mapper.SysMapper;
import com.jt.common.po.Cart;

public interface CartMapper extends SysMapper<Cart>{

    @Select("select * from tb_cart where item_id=#{itemId} and user_id=#{userId}")
    Cart findCartByUI(Cart cart);

}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
  <!--namespace="它是映射文件的唯一标识"-相当于配置文件的主键
  mapper接口调用方式，表明mapper接口/映射文件/表映射关系，用接口的全路径名称  -->
<mapper namespace="com.jt.cart.mapper.CartMapper">

</mapper>