Redisson之lock()和tryLock()的区别及说明

@Override
public boolean tryLock(long waitTime, long leaseTime, TimeUnit unit) throws InterruptedException {
    // 转成毫秒，后面都是以毫秒为单位
    long time = unit.toMillis(waitTime);
    // 当前时间
    long current = System.currentTimeMillis();
    // 线程ID-线程标识
    long threadId = Thread.currentThread().getId();
 
    // 尝试获取锁 tryAcquire() !!!
    Long ttl = tryAcquire(waitTime, leaseTime, unit, threadId);
        
    // 如果上面尝试获取锁返回的是null，表示成功；如果返回的是时间则表示失败。
    if (ttl == null) {
        return true;
    }
 
    // 剩余等待时间 = 最大等待时间 -（用现在时间 - 获取锁前的时间）
    time -= System.currentTimeMillis() - current;
 
    // 剩余等待时间 < 0 失败
    if (time <= 0) {
        acquireFailed(waitTime, unit, threadId);
        return false;
    }
 
    // 再次获取当前时间
    current = System.currentTimeMillis();
    // 重试逻辑，但不是简单的直接重试！
    // subscribe是订阅的意思
    RFuture<RedissonLockEntry> subscribeFuture = subscribe(threadId);
    // 如果在剩余等待时间内，收到了释放锁那边发过来的publish，则才会再次尝试获取锁
    if (!subscribeFuture.await(time, TimeUnit.MILLISECONDS)) {
        if (!subscribeFuture.cancel(false)) {
            subscribeFuture.onComplete((res, e) -> {
                if (e == null) {   
                    // 取消订阅
                    unsubscribe(subscribeFuture, threadId);
                }
            });
        }
        // 获取锁失败
        acquireFailed(waitTime, unit, threadId);
        return false;
    }
 
    try {
        // 又重新计算了一下，上述的等待时间
        time -= System.currentTimeMillis() - current;
        if (time <= 0) {
            acquireFailed(waitTime, unit, threadId);
            return false;
        }
 
        // 重试！
        while (true) {
            long currentTime = System.currentTimeMillis();
            ttl = tryAcquire(waitTime, leaseTime, unit, threadId);
 
            // 成功
            if (ttl == null) {
                return true;
            }
            
            // 又获取锁失败，再次计算上面的耗时
            time -= System.currentTimeMillis() - currentTime;
            if (time <= 0) {
                acquireFailed(waitTime, unit, threadId);
                return false;
            }
 
            currentTime = System.currentTimeMillis();
            // 采用信号量的方式重试！
            if (ttl >= 0 && ttl < time) {
                subscribeFuture.getNow().getLatch().tryAcquire(ttl, TimeUnit.MILLISECONDS);
            } else {
                subscribeFuture.getNow().getLatch().tryAcquire(time, TimeUnit.MILLISECONDS);
            }
            
            // 重新计算时间（充足就继续循环）
            time -= System.currentTimeMillis() - currentTime;
            if (time <= 0) {
                acquireFailed(waitTime, unit, threadId);
                return false;
            }
        }
    } finally {
        unsubscribe(subscribeFuture, threadId);
    }
}

private void lock(long leaseTime, TimeUnit unit, boolean interruptibly) throws InterruptedException {
 
	// 获取当前线程 ID
    long threadId = Thread.currentThread().getId();
    // 获取锁，正常获取锁则ttl为null，竞争锁时返回锁的过期时间
    Long ttl = tryAcquire(-1, leaseTime, unit, threadId);
    if (ttl == null) {
        return;
    }
		
    // 订阅锁释放事件
    // 如果当前线程通过 Redis 的 channel 订阅锁的释放事件获取得知已经被释放，则会发消息通知待等待的线程进行竞争
    RFuture<RedissonLockEntry> future = subscribe(threadId);
    if (interruptibly) {
        commandExecutor.syncSubscriptionInterrupted(future);
    } else {
        commandExecutor.syncSubscription(future);
    }
 
    try {
        while (true) {
            // 循环重试获取锁，直至重新获取锁成功才跳出循环
            // 此种做法阻塞进程，一直处于等待锁手动释放或者超时才继续线程    
            ttl = tryAcquire(-1, leaseTime, unit, threadId);
            if (ttl == null) {
                break;
            }
 
            if (ttl >= 0) {
                try {
                    future.getNow().getLatch().tryAcquire(ttl, TimeUnit.MILLISECONDS);
                } catch (InterruptedException e) {
                    if (interruptibly) {
                        throw e;
                    }
                    future.getNow().getLatch().tryAcquire(ttl, TimeUnit.MILLISECONDS);
                }
            } else {
                if (interruptibly) {
                    future.getNow().getLatch().acquire();
                } else {
                    future.getNow().getLatch().acquireUninterruptibly();
                }
            }
        }
    } finally {
        // 最后释放订阅事件
        unsubscribe(future, threadId);
    }
}