如何解决重复提交的问题(幂等)

关键点:识别哪些提交是同样的提交

解决方法：在页面设置token，利用redis事务的原子性。比如，在trade页面，点击提交订单，会生成一个token嵌入在页面中。点击结算时会验证token，解决重复提交的问题。

代码:

• controller"trade"

  @GetMapping("trade")
    @LoginRequire
    public String trade(HttpServletRequest request){
        String userId =(String)request.getAttribute("userId");
        //  用户地址  列表
        List<UserAddress> userAddressList = userService.getUserAddressList(userId);
  
        request.setAttribute("userAddressList",userAddressList);
  
        //  用户需要结账的商品清单
        List<CartInfo> checkedCartList = cartService.getCheckedCartList(userId);
        BigDecimal totalAmount = new BigDecimal("0");
        for (CartInfo cartInfo : checkedCartList) {
            BigDecimal cartInfoAmount = cartInfo.getSkuPrice().multiply(new BigDecimal(cartInfo.getSkuNum()));
            totalAmount= totalAmount.add(cartInfoAmount);
        }
  
        String token = orderService.genToken(userId);//生成token
  
        request.setAttribute("tradeNo",token);//request请求后面放token
  
        request.setAttribute("checkedCartList",checkedCartList);
  
        request.setAttribute("totalAmount",totalAmount);
  
        return  "trade";
    }

  • 生成token的方法

    @Override
    public String genToken(String userId) {
        //token  type   String  key   user:10201:trade_code  value token
        String token = UUID.randomUUID().toString();
        String tokenKey="user:"+userId+":trade_code";
        Jedis jedis = redisUtil.getJedis();
        jedis.setex(tokenKey,10*60,token);
        jedis.close();
    
        return token;
    }

• controller"submitOrder"

  @PostMapping("submitOrder")
    @LoginRequire
    public String submitOrder(OrderInfo orderInfo,HttpServletRequest request){
        String userId = (String) request.getAttribute("userId");
  
        String tradeNo = request.getParameter("tradeNo");//拿到token
  
        boolean isEnableToken = orderService.verifyToken(userId, tradeNo);//验证token
        if(!isEnableToken){
            request.setAttribute("errMsg","页面已失效，请重新结算！");
            return  "tradeFail";
        }
  
        }
  
        String orderId = orderService.saveOrder(orderInfo);
  
        // 删除购物车信息
        //  xxxx
        return "redirect://payment.gmall.com/index?orderId="+orderId;
    }

  • 验证token service

    @Override
        public boolean verifyToken(String userId, String token) {
            String tokenKey="user:"+userId+":trade_code";
            Jedis jedis = redisUtil.getJedis();
            String tokenExists = jedis.get(tokenKey);
            jedis.watch(tokenKey);//监控tokenkey
            Transaction transaction = jedis.multi();//开启事务
            if(tokenExists!=null&&tokenExists.equals(token)){
                transaction.del(tokenKey);//事务的删除，会在queue里面
            }
            List<Object> list = transaction.exec();//事务的提交，成功返回1，不成功会不进行任何操作，返回nill
            if(list!=null&&list.size()>0&&(Long)list.get(0)==1L){
                return true;
            }else{
                return false;
            }
        }