Backend Implementation of a SpringBoot-Based Seckill (Flash Sale) Project

The SeckillProject is a reference‑grade flash‑sale system built with SpringBoot, MyBatis, MySQL, Redis, and RabbitMQ, demonstrating core backend functionalities such as user login, product listing, product details, seckill ordering, and order details.

Technology Stack : Backend – SpringBoot, MyBatis, MySQL, RabbitMQ, Redis; Frontend – HTML, jQuery, Thymeleaf.

Key Implementation Details :

Double MD5 encryption of user passwords – the first hash protects the password in transit, the second protects stored credentials.

Distributed session maintenance – after successful authentication a UUID token is stored in Redis as token → userObject and also placed in a cookie; subsequent requests retrieve the user from Redis using the token.

Unified exception handling – a custom interceptor combined with @ControllerAdvice and @ExceptionHandler captures all exceptions and returns a unified response.

Page caching and object caching – rendered HTML pages are cached in Redis to reduce server load, and hot objects such as user, product, and order data are also cached; seckill products are pre‑loaded into Redis at startup.

Static page generation – AJAX is used for data fetching; after the first load the page and data are cached in the browser for faster subsequent access.

Memory flag + Redis pre‑decrement + RabbitMQ async processing – a local Map localOverMap tracks sold‑out items to avoid unnecessary Redis calls; Redis pre‑decrements stock, and successful requests are placed into a RabbitMQ queue for asynchronous order creation.

Oversell prevention – SQL update only succeeds when stock > 0; a unique index on (user_id, goods_id) prevents duplicate orders; optimistic locking with a version field adds another safety layer.

API rate limiting – a custom @AccessLimit annotation limits each user to a configurable number of requests within a time window.

Memory‑Flag and Redis Pre‑Decrement Code :

// System startup initializes all seckill product IDs into a map, stock = 0 means sold out
private Map
localOverMap = new HashMap<>();

// Memory flag to reduce Redis access
boolean over = localOverMap.get(goodsId);
if (over) {
    return Result.error(CodeMsg.MIAO_SHA_OVER);
}

// Redis pre‑decrement
long stock = redisService.decr(GoodsKey.getSeckillGoodsStock, "" + goodsId);
if (stock < 0) {
    localOverMap.put(goodsId, true);
    return Result.error(CodeMsg.MIAO_SHA_OVER);
}

// Check if user already placed an order
SeckillOrder order = orderService.getOrderByUserIdGoodsId(user.getId(), goodsId);
if (order != null) {
    return Result.error(CodeMsg.REPEATE_MIAOSHA);
}

// Push to message queue for async processing
SeckillMessage sm = new SeckillMessage();
sm.setUser(user);
sm.setGoodsId(goodsId);
sender.sendSeckillMessage(sm);

SQL for Stock Update (Oversell Guard) :

update seckill_goods set stock_count = stock_count - 1 where goods_id = #{goodsId} and stock_count > 0

The article also provides screenshots of the project structure, login page, product list, product details, order details after a successful seckill, and a link to download the full source code from Gitee.