ReadWriteLock读写锁

ReadWriteLock读写锁"/>

ReadWriteLock读写锁

ReadWriteLock读写锁

并发写需要等待，并发读等于无锁

• 读和写是同一把锁控制
• 只要写锁没释放，读锁就必须等待，反之一样
• 允许多个读锁 和 仅允许一个 写锁
• 读锁是共享锁，写锁是排他锁（互斥锁）
• 读写锁是同一把锁 RReadWriteLock lock = redissonClient.getReadWriteLock(“rw-lock”); get set取值也是同一个对象

需求：保证获取的是最新的数据？ 怎么操作？

更新完数据就释放写锁，定时任务 判断锁是否存在，如果锁存在，等锁释放后取值

这里是先执行写锁再执行读锁，当写锁释放时，写锁读锁同时渲染数据

 //写锁@GetMapping("/write")@ResponseBodypublic String writeValue(){//读写锁是同一把锁RReadWriteLock lock = redissonClient.getReadWriteLock("rw-lock");RLock writeLock = lock.writeLock();String uuid = "";try {uuid = UUID.randomUUID().toString();writeLock.lock();System.out.println("写锁占用成功");Thread.sleep(30000);redisTemplate.opsForValue().set("writeValue", uuid);} catch (Exception e) {e.printStackTrace();} finally {//写锁释放，读锁才能使用writeLock.unlock();System.out.println("写锁释放完成");}return uuid;}//读锁@GetMapping("/read")@ResponseBodypublic String readValue(){RReadWriteLock lock = redissonClient.getReadWriteLock("rw-lock");RLock readLock = lock.readLock();String uuid = "";try {readLock.lock();uuid = redisTemplate.opsForValue().get("writeValue");System.out.println("读锁占用成功");Thread.sleep(30000);} catch (Exception e) {e.printStackTrace();} finally {readLock.unlock();System.out.println("读锁释放完成");}return uuid;}

先读后写，读锁释放，写锁才能占用，这里就可以看出来读和写是同一把锁