（8）SprintBoot 2.X 秒杀功能的实现（秒杀业务逻辑处理）

1.秒杀业务逻辑

1.1 前端点击秒杀按钮进入秒杀业务逻辑

• 前端goods_detail.html里面的秒杀按钮点击之后提交/miaosha/do_miaosha，以POST类型提交，带有数据是秒杀商品的goodsId

1.2 秒杀业务逻辑

• 判断登录，如果用户为空，则返回至登录页面
• 根据商品id从数据库拿到商品库存，判断库存，库存足够，进行秒杀，不足则结束
• 判断同一用户是否重复秒杀
• 以上都通过，那么该用户可以秒杀商品
• 秒杀业务逻辑中的减库存和下订单是一个原子操作，是一个事务，所以需要@Transactional注解

注意：执行秒杀事务的时候，先生成详细订单，然后生成秒杀订单，为了进一步确保秒杀过程中一个用户只能秒杀一件商品，我们给秒杀订单表miaosha_order表添加一个唯一索引，如果再次插入相同的userid与goodsId相同的字段，那么将不会被允许，从而在事务中插入失败而回退

2. 代码实现

2.1 MiaoshaController的实现

	@RequestMapping("/miaosha")
	@Controller
	public class MiaoshaController{
	@Autowired
	GoodsService goodsService;
	@Autowired
	RedisService redisService;
	@Autowired
	MiaoshaService miaoshaService;
	@Autowired
	OrderService orderService;

	@RequestMapping("/do_miaosha")
	public String toList(Model model,MiaoshaUser user,@RequestParam("goodsId") Long goodsId) {
		model.addAttribute("user", user);
		//如果用户为空，则返回至登录页面
		if(user==null){
			return "login";
		}
		GoodsVo goodsvo=goodsService.getGoodsVoByGoodsId(goodsId);
		//判断商品库存，库存大于0，才进行操作，多线程下会出错
		int  stockcount=goodsvo.getStockCount();		
		if(stockcount<=0) {//失败			库存至临界值1的时候，此时刚好来了加入10个线程，那么库存就会-10
			model.addAttribute("errorMessage", CodeMsg.MIAOSHA_OVER_ERROR);
			return "miaosha_fail";
		}
		//判断是否重复秒杀 
		MiaoshaOrder order=orderService.getMiaoshaOrderByUserIdAndGoodsId(user.getId(),goodsId);
		if(order!=null) {//重复下单
			model.addAttribute("errorMessage", CodeMsg.REPEATE_MIAOSHA);
			return "miaosha_fail";
		}
		//可以秒杀，原子操作：1.库存减1，2.下订单是一个事务
		OrderInfo orderinfo=miaoshaService.miaosha(user,goodsvo);
		model.addAttribute("orderinfo", orderinfo);
		model.addAttribute("goods", goodsvo);
		return "order_detail";//跳转订单详情页
	}
}	

2.2 MiaoshaService的实现

• 只有减库存成功才能进入下订单环节，所以需要对reduceStock（）进行判断

@Service
public class MiaoshaService {
	@Autowired
	GoodsService goodsService;
	@Autowired
	OrderService orderService;
    //保证这三个操作，减库存 下订单 写入秒杀订单是一个事物
    @Transactional
    public OrderInfo miaosha(MiaoshaUser user, GoodsVo goods) {
        boolean success = goodsService.reduceStock(goods);
        if (success){
            //下订单 写入秒杀订单
            return orderService.createOrder(user, goods);
        }else {
            return null;
        }
    }	
}	

2.3 减库存的实现

2.3.1 GoodsService

@Service
public class GoodsService {
    @Autowired
    GoodsDao goodsDao;
    public List<GoodsVo> listGoodsVo() {
        return goodsDao.listGoodsVo();
    }
    public GoodsVo getGoodsVoByGoodsId(long goodsId) {
        return goodsDao.getGoodsVoByGoodsId(goodsId);
    }
    public boolean reduceStock(GoodsVo goods) {
        MiaoshaGoods g = new MiaoshaGoods();
        g.setGoodsId(goods.getId());
        return goodsDao.reduceStock(g) > 0 ;
    }
}

2.3.2 GoodsDao

@Mapper
public interface GoodsDao {
    @Select("select g.*, mg.miaosha_price, mg.stock_count, mg.start_date, mg.end_date from miaosha_goods mg left join goods g on mg.goods_id = g.id")
    public List<GoodsVo> listGoodsVo();

    @Select("select g.*, mg.miaosha_price, mg.stock_count, mg.start_date, mg.end_date from miaosha_goods mg left join goods g on mg.goods_id = g.id where g.id = #{goodsId}")
    public GoodsVo getGoodsVoByGoodsId(@Param("goodsId") long goodsId);

    @Update("update miaosha_goods set stock_count = stock_count - 1 where goods_id = #{goodsId} and stock_count > 0 ")
    public int  reduceStock(MiaoshaGoods g);
}

2.4 下订单的实现

2.4.1 OrderService

	@Service
	public class OrderService {
	@Autowired
	OrderDao orderDao;
	/**
	 * 根据用户userId和goodsId判断是否有者条订单记录，有则返回此纪录
	 * @param id
	 * @param goodsId
	 * @return
	 */
	public MiaoshaOrder getMiaoshaOrderByUserIdAndGoodsId(Long userId, Long goodsId) {
		return orderDao.getMiaoshaOrderByUserIdAndGoodsId(userId,goodsId);
	}
	
	/**
	 * 生成订单,事务
	 * @param user
	 * @param goodsvo
	 * @return
	 */
	@Transactional
	public OrderInfo createOrder(MiaoshaUser user, GoodsVo goodsvo) {
		//1.生成order_info
		OrderInfo orderInfo=new OrderInfo();
		orderInfo.setDeliveryAddrId(0L);//long类型 private Long deliveryAddrId;   L
		orderInfo.setCreateDate(new Date());
		orderInfo.setGoodsCount(1);
		orderInfo.setGoodsId(goodsvo.getId());
		//秒杀价格
		orderInfo.setGoodsPrice(goodsvo.getMiaoshaPrice());
		orderInfo.setOrderChannel(1);
		//订单状态  ---0-新建未支付  1-已支付  2-已发货  3-已收货
		orderInfo.setOrderStatus(0);
		//用户id
		orderInfo.setUserId(user.getId());
		//返回orderId
		//long orderId=
		orderDao.insert(orderInfo);
		//2.生成miaosha_order
		MiaoshaOrder miaoshaorder =new MiaoshaOrder();
		miaoshaorder.setGoodsId(goodsvo.getId());
		//将订单id传给秒杀订单里面的订单orderid
		miaoshaorder.setOrderId(orderInfo.getId());
		miaoshaorder.setUserId(user.getId());
		orderDao.insertMiaoshaOrder(miaoshaorder);
		return orderInfo;
	}	
	public OrderInfo getOrderByOrderId(long orderId) {
		return orderDao.getOrderByOrderId(orderId);
	}		
}

2.4.2 OrderDao

@Mapper
public interface OrderDao {
	@Select("select * from miaosha_order where user_id=#{userId} and goods_id=#{goodsId}")  
	public MiaoshaOrder getMiaoshaOrderByUserIdAndGoodsId(@Param("userId")Long userId, @Param("goodsId")Long goodsId);
	@Insert("insert into order_info (user_id,goods_id,goods_name,goods_count,goods_price,order_channel,order_status,create_date) values "
			+ "(#{userId},#{goodsId},#{goodsName},#{goodsCount},#{goodsPrice},#{orderChannel},#{orderStatus},#{createDate})")
	@SelectKey(keyColumn="id",keyProperty="id",resultType=long.class,before=false,statement="select last_insert_id()")
	public long insert(OrderInfo orderInfo);//使用注解获取返回值，返回上一次插入的id

	@Select("select * from order_info where user_id=#{userId} and goods_id=#{goodsId}")  
	public OrderInfo selectorderInfo(@Param("userId")Long userId, @Param("goodsId")Long goodsId);//使用注解获取返回值，返回上一次插入的id
	
	@Insert("insert into miaosha_order (user_id,goods_id,order_id) values (#{userId},#{goodsId},#{orderId})")
	public void insertMiaoshaOrder(MiaoshaOrder miaoshaorder);
	
	@Select("select * from order_info where id=#{orderId}")  
	public OrderInfo getOrderByOrderId(@Param("orderId")long orderId);    
	
}