浅谈redis分布式锁用法

使用redis的setnx命令进行实现

@Component
@Slf4j
public class RedisLock {
    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    /**
     * 加锁
     *
     * @param key
     * @param value
     * @return
     */
    public boolean lock(String key, String value) {
        if (stringRedisTemplate.opsForValue().setIfAbsent(key, value)) {
            return true;
        }
        String currentValue = stringRedisTemplate.opsForValue().get(key);
        //防止死锁
        if (!StringUtils.isEmpty(currentValue)
                && Long.parseLong(currentValue) < System.currentTimeMillis()) {
            String oldValue = stringRedisTemplate.opsForValue().getAndSet(key, value);
            if (!StringUtils.isEmpty(oldValue)
                    && oldValue.equals(currentValue)) {
                return true;
            }

        }
        return false;
    }

    /**
     * 解锁
     * @param key
     * @param value
     */
    public void unlock(String key, String value) {
        try {
            String currentValue = stringRedisTemplate.opsForValue().get(key);
            if (!StringUtils.isEmpty(currentValue)
                    && currentValue.equals(value)) {
                stringRedisTemplate.opsForValue().getOperations().delete(key);
            }
        } catch (Exception e) {
            log.error("【redis分布式锁】 解锁异常，{}", e);
        }

    }
}

demo

@Service
public class SecKillServiceImpl implements SeckillService {
    //超时时间10秒
    private static final int       TIMEOUT = 10 * 1000;
    @Autowired
    private              RedisLock redisLock;

    static Map<String, Integer> products;
    static Map<String, Integer> stock;
    static Map<String, String>  orders;

    {
        products = new HashMap<>();
        stock = new HashMap<>();
        orders = new HashMap<>();
        products.put("123456", 100000);
        stock.put("123456", 100000);
    }

    private String queryMap(String productId) {
        return "国庆活动，皮蛋粥特价，限量份"
                + products.get(productId)
                + "还剩：" + stock.get(productId) + "份"
                + "该商品成功下单用户数目："
                + orders.size() + "人";
    }

    @Override
    public  void orderProductMockDiffUser(String productId) {
        Long time = System.currentTimeMillis() + TIMEOUT;
        //加锁
        if (!redisLock.lock(productId, String.valueOf(time))) {
            throw new SellException(101, "哎呦喂，人也太多了，在试试");
        }

        Integer stockNum = stock.get(productId);
        if (stockNum == 0) {
            throw new SellException(100, "活动结束");
        } else {
            //下单
            orders.put(KeyUtil.genUniqueKey(), productId);
            //减库存
            stockNum = stockNum - 1;
            try {
                Thread.sleep(100);
            } catch (Exception e) {
                e.printStackTrace();
            }
            stock.put(productId, stockNum);
        }
        //解锁
        redisLock.unlock(productId, String.valueOf(time));
    }

    @Override
    public String querySecKillProductInfo(String productId) {
        return queryMap(productId);
    }
}