本文共 4777 字，大约阅读时间需要 15 分钟。

获取锁：

@Override	public String acquireLockWithTimeout(Jedis jedis,String lockName, long acquireTimeout, long lockTimeout) {
   		//Jedis jedis =getJedis();		try {
   			String identifier = UUID.randomUUID().toString();			String lockKey = "lock:" + lockName;			int lockExpire = (int) (lockTimeout / 1000);			long endTime = System.currentTimeMillis() + acquireTimeout;			while (System.currentTimeMillis() < endTime) {
   				logger.info("acquireLockWithTimeout->jedis->"+jedis);				// 尝试设置key-value值，并且key不存在				if (jedis.setnx(lockKey, identifier) == 1) {
   					// key不存在，并且设置成功，获取锁成功					jedis.expire(lockKey, lockExpire);					return identifier;				}								//处理其他占用锁并且无法释放锁的情况				if (jedis.ttl(lockKey) == -1) {
   					// key 存在但没有设置剩余生存时间					jedis.expire(lockKey, lockExpire);				}				try {
   					Thread.sleep(1);				} catch (InterruptedException ie) {
   					Thread.currentThread().interrupt();				}			}		}catch(Exception e) {
   			e.printStackTrace();		}finally {
   			/*if(jedis!=null) {				jedis.close();			}*/		}		return null;	}

流程图

释放锁：

@Override	public boolean releaseLock(Jedis jedis,String lockName, String identifier) {
   		//Jedis jedis = getJedis();		try {
   			String lockKey = "lock:" + lockName;			while (true) {
   				// 监控key				jedis.watch(lockKey);				if (identifier.equals(jedis.get(lockKey))) {
   					Transaction trans = jedis.multi();					trans.del(lockKey);					List

$删除的时候需要注意先监控key，然后比较value，再删除，之所以需要监控，是因为再比较后可能值会出现变化$

测试：

@RunWith(SpringRunner.class)@SpringBootTestpublic class LockServiceTest {
   	private static final Logger logger = LoggerFactory.getLogger(LockServiceTest.class);	@Autowired	private RedisService redisService;	@Autowired	private RedisTemplate
   
     redisTemplate;		private AtomicInteger atomicI = new AtomicInteger(0);	@Test	public void testJedis() {
   		/*ScheduledExecutorService executorService = Executors.newScheduledThreadPool(10);		// for (int i = 0; i < 10; i++) {		// 定时执行任务，每隔10秒钟执行一次		executorService.scheduleWithFixedDelay(new Runnable() {			@Override			public void run() {				Jedis jedis = redisService.getJedis();				String value = jedis.get("aaa");				logger.info("=================【{}】=================", value);			}		}, 0, 10, TimeUnit.SECONDS);		// }*/			}
   

@Test	public void testLock() {
   		ExecutorService fixedThreadPool = Executors.newFixedThreadPool(5);		for (int i = 0; i < 10; i++) {
   			// 定时执行任务，每隔500毫秒执行一次			fixedThreadPool.execute(new Runnable() {
   				@Override				public void run() {
   					Jedis jedis=null;					atomicI.incrementAndGet();					String lockName = "lock01";					String id = "";					try {
   						long acquireTimeout = 10000;						long lockTimeout = 10000;						long startTime = System.currentTimeMillis();												id = redisService.acquireLockWithTimeout(jedis,lockName, acquireTimeout, lockTimeout);						long endTime = System.currentTimeMillis();						if (id != null) {
   							logger.info("获取锁成功，id:【{}】花费时间：【{}】" ,id,(endTime - startTime));						} else {
   							logger.info("获取锁失败，花费时间：【{}】",(endTime - startTime));						}						Thread.sleep(1000);					} catch (Exception e) {
   						e.printStackTrace();					} finally {
   						if (id != "" && id != null) {
   							logger.info("开始释放锁id:【{}】",id);							redisService.releaseLock(jedis,lockName, id);						} else {
   							logger.info("无锁需要释放");						}					}				}			});		}				while(true) {
   			if(fixedThreadPool.isTerminated()) {
   				System.out.println("run over");				System.out.println("i="+atomicI);				break;			}		}	}}

如上的实现方式在主备、哨兵模式下会存在问题，比如在主节点执行了set后，然后宕机了，从节点同步获取到锁信息，那么其他客户端也会再次获取到锁。然后就出现了红锁。

redission分布式锁的实现

参考：http://www.redis.cn/topics/distlock.html

摘自《Redis实战》。

转载地址：http://juhvb.baihongyu.com/