Redisson 加锁解锁的实现

private void sumLock() {
    lock = redissonClient.getLock("sum-lock");
    
    boolean b = lock.tryLock();
    if (!b) {
        log.info("获取不到锁");
        return;
    }
    
    try {
        for (int j = 0; j < 20000; j++) {
            ++sum;
        }
    } finally {
        lock.unlock();
    }
    
}

public RLock getLock(String name) {
  // 实例化 RedissonLock，参数为指令执行器和锁名称
  return new RedissonLock(this.connectionManager.getCommandExecutor(), name);
}

public RedissonLock(CommandAsyncExecutor commandExecutor, String name) {
  super(commandExecutor, name);
  // 命令执行器，用于执行lua脚本
  this.commandExecutor = commandExecutor;
  // 连接管理器的ID
  this.id = commandExecutor.getConnectionManager().getId();
  // 锁续期时间（看门狗），锁默认续期时间是 30s。
  this.internalLockLeaseTime = commandExecutor.getConnectionManager().getCfg().getLockWatchdogTimeout();
  this.entryName = this.id + ":" + name;
  this.pubSub = commandExecutor.getConnectionManager().getSubscribeService().getLockPubSub();
}

@Override
public boolean tryLock() {
  return get(tryLockAsync());
}

@Override
public RFuture<Boolean> tryLockAsync() {
  return tryLockAsync(Thread.currentThread().getId());
}

@Override
public RFuture<Boolean> tryLockAsync(long threadId) {
  return tryAcquireOnceAsync(-1, -1, null, threadId);
}

private RFuture<Boolean> tryAcquireOnceAsync(long waitTime, long leaseTime, TimeUnit unit, long threadId) {
  // 由于我们调用tryLocak没有传递任何参数，leaseTime默认为-1，不走判断
  if (leaseTime != -1) {
    return tryLockInnerAsync(waitTime, leaseTime, unit, threadId, RedisCommands.EVAL_NULL_BOOLEAN);
  }
 
  // 调用获取锁 枷锁的主要逻辑在这里
  RFuture<Boolean> ttlRemainingFuture = tryLockInnerAsync(waitTime,
                        commandExecutor.getConnectionManager().getCfg().getLockWatchdogTimeout(),
                        TimeUnit.MILLISECONDS, threadId, RedisCommands.EVAL_NULL_BOOLEAN);
 
  ttlRemainingFuture.onComplete((ttlRemaining, e) -> {
    // 如果发生异常那么直接放回了
    if (e != null) {
      return;
    }

    // 锁续期
    if (ttlRemaining) {
      scheduleExpirationRenewal(threadId);
    }
  });
  // 返回结果
  return ttlRemainingFuture;
}

<T> RFuture<T> tryLockInnerAsync(long waitTime, long leaseTime, TimeUnit unit, long threadId, RedisStrictCommand<T> command) {
    // 将时间转化为毫秒
    internalLockLeaseTime = unit.toMillis(leaseTime);
    // 执行脚本
    return evalWriteAsync(getName(), LonGCodec.INSTANCE, command,
            "if (redis.call('exists', KEYS[1]) == 0) then " +
                    "redis.call('hincrby', KEYS[1], ARGV[2], 1); " +
                    "redis.call('pexpire', KEYS[1], ARGV[1]); " +
                    "return nil; " +
                    "end; " +
                    "if (redis.call('hexists', KEYS[1], ARGV[2]) == 1) then " +
                    "redis.call('hincrby', KEYS[1], ARGV[2], 1); " +
                    "redis.call('pexpire', KEYS[1], ARGV[1]); " +
                    "return nil; " +
                    "end; " +
                    "return redis.call('pttl', KEYS[1]);",
            Collections.singletonList(getName()), internalLockLeaseTime, getLockName(threadId));
}

@Override
public void unlock() {
  try {
    get(unlockAsync(Thread.currentThread().getId()));
  } catch (RedisException e) {
    if (e.getCause() instanceof IllegalMonitorStateException) {
      throw (IllegalMonitorStateException) e.getCause();
    } else {
      throw e;
    }
  }
}

@Override
public RFuture<Void> unlockAsync(long threadId) {
  RPromise<Void> result = new RedissonPromise<Void>();
  // 释放锁的逻辑主要这里
  RFuture<Boolean> future = unlockInnerAsync(threadId);

  future.onComplete((opStatus, e) -> {
    cancelExpirationRenewal(threadId);

    if (e != null) {
      result.tryFailure(e);
      return;
    }

    if (opStatus == null) {
      IllegalMonitorStateException cause = new IllegalMonitorStateException("attempt to unlock lock, not locked by current thread by node id: "
          + id + " thread-id: " + threadId);
      result.tryFailure(cause);
      return;
    }

    result.trySuccess(null);
  });

  return result;
}

protected RFuture<Boolean> unlockInnerAsync(long threadId) {
    return evalWriteAsync(getName(), LongCodec.INSTANCE, RedisCommands.EVAL_BOOLEAN,
            "if (redis.call('hexists', KEYS[1], ARGV[3]) == 0) then " +
                    "return nil;" +
                    "end; " +
                    "local counter = redis.call('hincrby', KEYS[1], ARGV[3], -1); " +
                    "if (counter > 0) then " +
                    "redis.call('pexpire', KEYS[1], ARGV[2]); " +
                    "return 0; " +
                    "else " +
                    "redis.call('del', KEYS[1]); " +
                    "redis.call('publish', KEYS[2], ARGV[1]); " +
                    "return 1; " +
                    "end; " +
                    "return nil;",
            Arrays.asList(getName(), getChannelName()), LockPubSub.UNLOCK_MESSAGE, internalLockLeaseTime, getLockName(threadId));
}