使用Redis实现一个安全可靠的分布式锁

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
  	<version>${your-spring-boot-version}</version>
</dependency>

spring.redis.database=0
spring.redis.host=localhost
spring.redis.port=6379

@Configuration
public class RedisConfig {

    // 自己定义了一个 RedisTemplate
    @Bean
    @SuppressWarnings("all")
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory factory)
        throws UnknownHostException {
        // 我们为了自己开发方便，一般直接使用 <String, Object>
        RedisTemplate<String, Object> template = new RedisTemplate<String,
            Object>();
        template.setConnectionFactory(factory);
        // Json序列化配置
        Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);

        ObjectMapper om = new ObjectMapper();
        om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        jackson2JsonRedisSerializer.setObjectMapper(om);
        // String 的序列化
        StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
        // key采用String的序列化方式
        template.setKeySerializer(stringRedisSerializer);
        // hash的key也采用String的序列化方式
        template.setHashKeySerializer(stringRedisSerializer);
        // value序列化方式采用jackson
        template.setValueSerializer(jackson2JsonRedisSerializer);
        // hash的value序列化方式采用jackson
        template.setHashValueSerializer(jackson2JsonRedisSerializer);
        template.afterPropertiesSet();
        return template;
    }
}

@Service
public class RedisLock {

    @Resource
    private RedisTemplate<String, Object> redisTemplate;

    /**
     * 加锁，最多等待maxWait毫秒
     *
     * @param lockKey   锁定key
     * @param lockValue 锁定value
     * @param timeout   锁定时长（毫秒）
     * @param maxWait   加锁等待时间（毫秒）
     * @return true-成功，false-失败
     */
    public boolean tryAcquire(String lockKey, String lockValue, int timeout, long maxWait) {
        long start = System.currentTimeMillis();

        while (true) {
            // 尝试加锁
            Boolean ret = redisTemplate.opsForValue().setIfAbsent(lockKey, lockValue, timeout, TimeUnit.MILLISECONDS);
            if (!ObjectUtils.isEmpty(ret) && ret) {
                return true;
            }

            // 计算已经等待的时间
            long now = System.currentTimeMillis();
            if (now - start > maxWait) {
                return false;
            }

            try {
                Thread.sleep(200);
            } catch (Exception ex) {
                return false;
            }
        }
    }

    /**
     * 释放锁
     *
     * @param lockKey   锁定key
     * @param lockValue 锁定value
     * @return true-成功，false-失败
     */
    public boolean releaseLock(String lockKey, String lockValue) {
        // lua脚本
        String script = "if redis.call('get',KEYS[1]) == ARGV[1] then return redis.call('del',KEYS[1]) else return 0 end";

        DefaultRedisScript<Long> redisScript = new DefaultRedisScript<>(script, Long.class);
        Long result = redisTemplate.opsForValue().getOperations().execute(redisScript, Collections.singletonList(lockKey), lockValue);
        return result != null && result > 0L;
    }
}

@SpringBootTest
class RedisDistLockDemoApplicationTests {

    @Resource
    private RedisLock redisLock;

    @Test
    public void testLock() {
        redisLock.tryAcquire("abcd", "abcd", 5 * 60 * 1000, 5 * 1000);
        redisLock.releaseLock("abcd", "abcd");
    }
}

    @Test
    public void testRedLock() throws InterruptedException {

        Config config = new Config();
        config.useSingleServer().setAddress("redis://127.0.0.1:6379");
        final RedissonClient client = Redisson.create(config);

        // 获取锁实例
        final RLock lock = client.getLock("test-lock");

        // 加锁
        lock.lock(60 * 1000, TimeUnit.MILLISECONDS);
        try {
            // 假装做些什么事情
            Thread.sleep(50 * 1000);
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            //解锁
            lock.unlock();
        }
    }