二、高效的分布式锁框架redisson

一、参考文献

官方文档:https://github.com/redisson/redisson

查看配置详细信息:

 https://github.com/redisson/redisson/wiki/Table-of-Content

二、redisson介绍

1.概念

Redisson是一个在Redis的基础上实现的Java驻内存数据网格(In-Memory Data Grid)。它不仅提供了一系列的分布式的Java常用对象,还提供了许多分布式服务。其中包括(BitSet, Set, Multimap, SortedSet, Map, List, Queue, BlockingQueue, Deque, BlockingDeque, Semaphore, Lock, AtomicLong, CountDownLatch, Publish / Subscribe, Bloom filter, Remote service, Spring cache, Executor service, Live Object service, Scheduler service) Redisson提供了使用Redis的最简单和最便捷的方法。Redisson的宗旨是促进使用者对Redis的关注分离(Separation of Concern),从而让使用者能够将精力更集中地放在处理业务逻辑上。

三、redisson的测试

1.可重用锁(Reentrant Lock)

RLock lock = redisson.getLock("anyLock");
// 最常见的使用方法
lock.lock();

如等待锁时间释放,或直接返回结果,不等待

// 加锁以后10秒钟自动解锁
// 无需调用unlock方法手动解锁
lock.lock(10, TimeUnit.SECONDS);

// 尝试加锁,最多等待100秒,上锁以后10秒自动解锁
boolean res = lock.tryLock(100, 10, TimeUnit.SECONDS);
if (res) {
   try {
     ...
   } finally {
       lock.unlock();
   }
}

2.公平锁(Fair Lock)

RLock fairLock = redisson.getFairLock("anyLock");
// 最常见的使用方法
fairLock.lock();

3.读写锁(ReadWriteLock)

    @GetMapping("/read")
    @ResponseBody
    public String read() {
        RReadWriteLock lock = redissonClient.getReadWriteLock("ReadWrite-Lock");
        RLock rLock = lock.readLock();
        String s = "";
        try {
            rLock.lock();
            System.out.println("读锁加锁"+Thread.currentThread().getId());
            Thread.sleep(5000);
            s= redisTemplate.opsForValue().get("lock-value");
        }finally {
            rLock.unlock();
            return "读取完成:"+s;
        }
    }

    @GetMapping("/write")
    @ResponseBody
    public String write() {
        RReadWriteLock lock = redissonClient.getReadWriteLock("ReadWrite-Lock");
        RLock wLock = lock.writeLock();
        String s = UUID.randomUUID().toString();
        try {
            wLock.lock();
            System.out.println("写锁加锁"+Thread.currentThread().getId());
            Thread.sleep(10000);
            redisTemplate.opsForValue().set("lock-value",s);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            wLock.unlock();
            return "写入完成:"+s;
        }
    }

写锁会阻塞读锁,但是读锁不会阻塞读锁,但读锁会阻塞写锁

总之含有写的过程都会被阻塞,只有读读不会被阻塞

4.信号量(Semaphore)

停车场例子:信号量为存储在redis中的一个数字,当这个数字大于0时,即可以调用acquire()方法增加数量,也可以调用release()方法减少数量,但是当调用release()之后小于<=0的话方法就会阻塞,直到数字大于0

@GetMapping("/park")
@ResponseBody
public String park() {
    RSemaphore park = redissonClient.getSemaphore("park");
    try {
        park.acquire(5);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    return "停车";
}

@GetMapping("/go")
@ResponseBody
public String go() {
    RSemaphore park = redissonClient.getSemaphore("park");
    park.release(1);
    return "开走";
}

 5.闭锁(DownLatch)

关门例子:设置5个人,直到所有人离开为0时,关门接口才执行完

@GetMapping("/closeDoor")
    @ResponseBody
    public String closeDoor() {
        RCountDownLatch latch = redissonClient.getCountDownLatch("CountDownLatch");
        try {
            latch.trySetCount(5);
            latch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "关门";
    }

    @GetMapping("/go")
    @ResponseBody
    public String go() {
        RCountDownLatch latch = redissonClient.getCountDownLatch("CountDownLatch");
        latch.countDown();
        return "走人";
    }

 

 项目地址https://gitee.com/pan_quan_lin/yqzj-cloud-study/tree/master/yqzj-redission

posted on 2021-01-10 00:20  剑与心声  阅读(538)  评论(0编辑  收藏  举报