java 秒杀缓存 详细代码

Java 秒杀系统中使用缓存可以提高系统的并发处理能力和性能，减轻数据库的压力。下面是一个简单的基于 Redis 的秒杀缓存实现代码示例：

1. 引入 Redis 相关依赖：

<dependency>
    <groupId>redis.clients</groupId>
    <artifactId>jedis</artifactId>
    <version>2.9.0</version>
</dependency>

2. 创建 Redis 连接池：

public class RedisPoolUtil {
    private static JedisPool jedisPool = null;

    static {
        JedisPoolConfig jedisPoolConfig = new JedisPoolConfig();
        jedisPoolConfig.setMaxIdle(10);
        jedisPoolConfig.setMaxTotal(100);
        jedisPoolConfig.setMaxWaitMillis(10000);
        jedisPool = new JedisPool(jedisPoolConfig, "localhost", 6379);
    }

    public static Jedis getJedis() {
        return jedisPool.getResource();
    }

    public static void releaseJedis(Jedis jedis) {
        if (jedis != null) {
            jedis.close();
        }
    }
}

3. 编写秒杀缓存相关代码：

public class SeckillRedisDaoImpl implements SeckillRedisDao {
    private static final String SECKILL_KEY_PREFIX = "seckill:";
    private static final String SECKILL_STOCK_KEY_PREFIX = "seckill:stock:";
    private static final String SECKILL_USER_KEY_PREFIX = "seckill:user:";

    @Override
    public boolean putSeckill(long seckillId, long startTime, long endTime) {
        Jedis jedis = RedisPoolUtil.getJedis();
        try {
            String key = SECKILL_KEY_PREFIX + seckillId;
            Map<String, String> map = new HashMap<>();
            map.put("startTime", String.valueOf(startTime));
            map.put("endTime", String.valueOf(endTime));
            jedis.hmset(key, map);
            return true;
        } finally {
            RedisPoolUtil.releaseJedis(jedis);
        }
    }

    @Override
    public Seckill getSeckill(long seckillId) {
        Jedis jedis = RedisPoolUtil.getJedis();
        try {
            String key = SECKILL_KEY_PREFIX + seckillId;
            Map<String, String> map = jedis.hgetAll(key);
            if (map == null || map.isEmpty()) {
                return null;
            }
            Long startTime = Long.valueOf(map.get("startTime"));
            Long endTime = Long.valueOf(map.get("endTime"));
            return new Seckill(seckillId, startTime, endTime);
        } finally {
            RedisPoolUtil.releaseJedis(jedis);
        }
    }

    @Override
    public boolean putStock(long seckillId, long stockCount) {
        Jedis jedis = RedisPoolUtil.getJedis();
        try {
            String key = SECKILL_STOCK_KEY_PREFIX + seckillId;
            jedis.set(key, String.valueOf(stockCount));
            return true;
        } finally {
            RedisPoolUtil.releaseJedis(jedis);
        }
    }

    @Override
    public long getStock(long seckillId) {
        Jedis jedis = RedisPoolUtil.getJedis();
        try {
            String key = SECKILL_STOCK_KEY_PREFIX + seckillId;
            String value = jedis.get(key);
            if (value == null) {
                return -1;
            }
            return Long.valueOf(value);
        } finally {
            RedisPoolUtil.releaseJedis(jedis);
        }
    }

    @Override
    public boolean putUser(long seckillId, long userId) {
        Jedis jedis = RedisPoolUtil.getJedis();
        try {
            String key = SECKILL_USER_KEY_PREFIX + seckillId;
            jedis.sadd(key, String.valueOf(userId));
            return true;
        } finally {
            RedisPoolUtil.releaseJedis(jedis);
        }
    }

    @Override
    public boolean isUserExist(long seckillId, long userId) {
        Jedis jedis = RedisPoolUtil.getJedis();
        try {
            String key = SECKILL_USER_KEY_PREFIX + seckillId;
            return jedis.sismember(key, String.valueOf(userId));
        } finally {
            RedisPoolUtil.releaseJedis(jedis);
        }
    }
}

以上代码实现了 Redis 缓存中秒杀商品基本信息、库存数量和用户购买记录的缓存操作。需要注意的是，对于秒杀缓存的实现，还需要考虑缓存的更新和缓存与数据库之间的一致性等问题。