电商秒杀项目-交易模块

首先创建交易模型，然后根据模型创建表，生成实体。然后创建service，写创建订单的方法。
创建订单
1校验下单状态 商品存在？用户合法？购买数量正确？

@Override
    public ItemModel getItemById(Integer id) {
        ItemDO itemDO = itemDOMapper.selectByPrimaryKey(id);
        if (itemDO==null){
            return null;
        }
        ItemStockDO itemStockDO = itemStockDOMapper.selectByItemId(itemDO.getId());

        ItemModel itemModel = convertItemModelFromItemDO(itemDO,itemStockDO);
        return itemModel;
    }

 @Override
    public UserModel getUserById(Integer id) {
        userDO userDO = userDOMapper.selectByPrimaryKey(id);

        if (userDO == null){
            return null;
        }
        UserPasswordDO userPasswordDO = userPasswordDOMapper.selectByUserId(id);

        return converFronDataObject(userDO,userPasswordDO);
    }

2落单减库存（下单就锁库存），支付减库存（支付才去减库存）这里使用落单减库存
在itemservice中创建一个减库存的方法decreaseStock，接收商品id和数量的参数。然后在库存的mapper.xml中新增

 <update id="decreaseStock">
    update item_stock
    set stock = stock - #{amount}
    where item_id = #{itemId} and stock >= #{amount}
  </update>

ItemStockDOMapper.Java中

int decreaseStock(@Param("itemId") Integer itemId,@Param("amount") Integer amount);

然后在decreaseStock中调用itemStockDOMapper的decreaseStock，接收返回值，根据返回值来确定修改结果

@Override
    public boolean decreaseStock(Integer itemId,Integer amount) throws BusinessException {
        int affectedRow = itemStockDOMapper.decreaseStock(itemId,amount);
        if (affectedRow>0){
            return true;
        }else {
            return false;
        }
    }

3.生成交易流水号

自增序列：在数据库中建一张表，包含name，currentValue，step。step是步长。在使用时每次都根据name来取对应的currentValue，并且取出来之后要更新currentValue，使它加上它的一个步长，这样就可以保证每次的自增序列不会重复

根据name获取tSequence：

 <select id="getSequenceByName" parameterType="java.lang.String" resultMap="BaseResultMap">
    select
    <include refid="Base_Column_List" />
    from sequence_info
    where name = #{name,jdbcType=VARCHAR} for update
  </select>

生成流水号：

@Transactional(propagation = Propagation.REQUIRES_NEW)
public String generateOderNo(){
    //订单号16位
    StringBuilder stringBuilder = new StringBuilder();
    //前8位是年月日
    LocalDateTime now = LocalDateTime.now();
    String nowDate = now.format(DateTimeFormatter.ISO_DATE).replace("-","");
    stringBuilder.append(nowDate);

    //中间6位为自增序列
    int sequence = 0;
    SequenceDO sequenceDO = sequenceDOMapper.getSequenceByName("order_info");
    sequence = sequenceDO.getCurrentValue();
    sequenceDO.setCurrentValue(sequenceDO.getCurrentValue()+sequenceDO.getStep());
    sequenceDOMapper.updateByPrimaryKeySelective(sequenceDO);
    String sequencestr = String.valueOf(sequence);
    for (int i=0;i<6-sequencestr.length();i++){
        stringBuilder.append(0);
    }
    stringBuilder.append(sequencestr);

    //最后2位为分库分表位 暂时写死
    stringBuilder.append("00");

    return stringBuilder.toString();

}

private OrderInfoDO convertDOFromModel(orderModel orderModel){
        if (orderModel==null){
            return null;
        }
        OrderInfoDO orderInfoDO = new OrderInfoDO();

        orderInfoDO.setId(orderModel.getId());
        orderInfoDO.setAmount(orderModel.getAmount());
        orderInfoDO.setItemid(orderModel.getItemId());
        orderInfoDO.setItemprice(orderModel.getItemPrice().doubleValue());
        orderInfoDO.setOrderprice(orderModel.getOrderPrice().doubleValue());
        orderInfoDO.setUserid(orderModel.getUserId());
        return orderInfoDO;
    }

4订单入库
5加上商品销量
在xml中增加一个方法然后在itemservice中调用

<update id="increaseSales" parameterType="com.miaosha3.dataobject.ItemDO">
    update item
    set sales = sales + #{amount},
    where id = #{id,jdbcType=INTEGER}
  </update>

@Override
    @Transactional
    public void increaseSales(Integer itemId, Integer amount) {
        itemDOMapper.increaseSales(itemId,amount);
    }

6返回前端

 @Override
    @Transactional
    public orderModel createOrder(Integer userId, Integer itemId, Integer amount) throws BusinessException {
        //校验下单状态 商品存在？用户合法？购买数量正确？
        ItemModel itemModel = itemService.getItemById(itemId);
        if (itemModel==null){
            throw new BusinessException(EmBusinessError.PAEAMETER_VALIDATION_ERROR,"商品信息不合法");
        }
        if (itemModel.getStock()<amount){
            throw new BusinessException(EmBusinessError.PAEAMETER_VALIDATION_ERROR,"商品数量不足");
        }
        UserModel userModel = userService.getUserById(userId);
        if (userModel==null){
            throw new BusinessException(EmBusinessError.PAEAMETER_VALIDATION_ERROR,"用户信息不存在");
        }
        if (amount <= 0 ||amount > 99){
            throw new BusinessException(EmBusinessError.PAEAMETER_VALIDATION_ERROR,"数量信息不正确");
        }



        //落单减库存（下单就锁库存），支付减库存（支付才去减库存）这里使用落单减库存
        boolean result = itemService.decreaseStock(itemId,amount);
        if (!result){
            throw new BusinessException(EmBusinessError.STOCK_NOT_ENOUGH);

        }


        //订单入库
        orderModel orderModel = new orderModel();
        orderModel.setUserId(userId);
        orderModel.setItemId(itemId);
        orderModel.setAmount(amount);
        orderModel.setItemPrice(itemModel.getPrice());
        orderModel.setOrderPrice(orderModel.getItemPrice().multiply(
                new BigDecimal(amount)
        ));

        //生成交易流水号
        orderModel.setId(generateOderNo());
        OrderInfoDO orderInfoDO = convertDOFromModel(orderModel);
        orderInfoDOMapper.insertSelective(orderInfoDO);


        //加上商品销量
        itemService.increaseSales(itemId,amount);


        //返回前端


        return null;
    }

封装下单请求

在控制器接收请求，在封装请求调用service

 @RequestMapping(value = "/createorder",method = {RequestMethod.POST},consumes = {CONTENT_TYPE_FORMED})
    @ResponseBody
    public CommonReturnType createOrder(@RequestParam(name = "itemId")Integer itemId,
                                        @RequestParam(name = "amount")Integer amount) throws BusinessException {
        //获取用户登录信息
        Boolean isLogin = (Boolean) httpServletRequest.getSession().getAttribute("IS_LOGIN");//登录成功保存的session
        if (isLogin == null || !isLogin.booleanValue()){
            throw new BusinessException(EmBusinessError.NOT_LOGIN);
        }
        UserModel userModel = (UserModel) httpServletRequest.getSession().getAttribute("LOGIN_USER");
        orderModel orderModel = orderService.createOrder(userModel.getId(),itemId,amount);

        return CommonReturnType.create(null);
    }