缓存-分布式锁-Redisson-读写锁补充

读写锁：它的特点就是：保证一定能读到最新数据，修改期间，写锁是一个排它锁（互斥锁、独享锁），读锁是一个共享锁

• 写锁没释放读锁必须等待
• 读 + 读 ：相当于无锁，并发读，只会在Redis中记录好，所有当前的读锁。他们都会同时加锁成功
• 写 + 读 ：必须等待写锁释放
• 写 + 写 ：阻塞方式
• 读 + 写 ：有读锁。写也需要等待
• 只要有读或者写的存都必须等待

@GetMapping(value = "/write")
@ResponseBody
public String writeValue() {
    String s = "";
    RReadWriteLock readWriteLock = redisson.getReadWriteLock("rw-lock");
    RLock rLock = readWriteLock.writeLock();
    try {
        //1、改数据加写锁，读数据加读锁
        rLock.lock();
        s = UUID.randomUUID().toString();
        ValueOperations ops = stringRedisTemplate.opsForValue();
        ops.set("writeValue",s);
        TimeUnit.SECONDS.sleep(10);
    } catch (InterruptedException e) {
        e.printStackTrace();
    } finally {
        rLock.unlock();
    }

    return s;
}

@GetMapping(value = "/read")
@ResponseBody
public String readValue() {
    String s = "";
    RReadWriteLock readWriteLock = redisson.getReadWriteLock("rw-lock");
    //加读锁
    RLock rLock = readWriteLock.readLock();
    try {
        rLock.lock();
        ValueOperations ops = stringRedisTemplate.opsForValue();
        s = ops.get("writeValue");
        try { TimeUnit.SECONDS.sleep(10); } catch (InterruptedException e) { e.printStackTrace(); }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        rLock.unlock();
    }

    return s;
}