Redis分布式锁实现实例

今天面试官问Redis分布式锁实现代码简单步骤，其中有一点面试官坚持说set操作和超时设置必须是2行代码，我当时懵了一下，我只能说这违反了“原子”操作，以下是我的实现示例代码：

上锁：

	@Override
	public boolean lock(String lockKey, String requestId, Long expireTime) {

		Assert.isTrue(StringUtils.isNotBlank(lockKey), "lockKey不能为空");
		Assert.isTrue(StringUtils.isNotBlank(requestId), "请求标识不能为空");

		Object result = stringRedisTemplate.execute(new RedisCallback<Boolean>() {

			@Override
			public Boolean doInRedis(RedisConnection connection) throws DataAccessException {

				Expiration expiration = Expiration.milliseconds(null == expireTime ? 1000L * 60 : expireTime);
				byte[] key = lockKey.getBytes(Charset.forName("UTF-8"));
				byte[] value = requestId.getBytes(Charset.forName("UTF-8"));

				return connection.set(key, value, expiration, SetOption.SET_IF_ABSENT);

			}
		});

		return (null == result) ? false : result.equals(true);

	}

释放锁：

	@Override
	public boolean unlock(String lockKey, String requestId) {

		Assert.isTrue(StringUtils.isNotBlank(lockKey), "lockKey不能为空");
		Assert.isTrue(StringUtils.isNotBlank(requestId), "请求标识不能为空");

		String lua = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";

		Object result = stringRedisTemplate.execute(new RedisCallback<Boolean>() {

			@Override
			public Boolean doInRedis(RedisConnection connection) throws DataAccessException {

				byte[] script = lua.getBytes(Charset.forName("UTF-8"));
				byte[] key = lockKey.getBytes(Charset.forName("UTF-8"));
				byte[] value = requestId.getBytes(Charset.forName("UTF-8"));

				Long result = connection.eval(script, ReturnType.INTEGER, 1, key, value);
				return (null == result ? false : result.equals(1L));

			}
		});

		return (null == result) ? false : result.equals(true);

		/* 若redis是2.6.0以下版本，则不支持lua脚本，只能降级采用redisTemplate.delete解锁，但不能保证原子操作 */

	}

spring boot之Redis分布式锁示例代码