用redis实现分布式锁，解决高并发时的线程安全问题

最新推荐文章于 2025-06-26 22:23:49 发布

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最新推荐文章于 2025-06-26 22:23:49 发布 · 置顶 · 1.2w 阅读

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#分布式锁

本文通过实例代码展示了如何利用Redis实现分布式锁解决多线程并发时的线程安全问题，特别是在抢购场景中避免票数混乱。讨论了volatile关键字的作用，以及在分布式锁中设置超时时间以防止死锁的重要性。最后提到了在Spring中使用Redis可能出现的‘ERR EXEC without MULTI’错误及其原因。

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实际工作中，经常会遇到多线程并发时的类似抢购的功能，本篇描述一个简单的redis分布式锁实现的多线程抢票功能。

直接上代码。首先按照慣例，給出一個错误的示范：

我们可以看看，当20个线程一起来抢10张票的时候，会发生什么事。

package com.tiger.utils;

public class TestMutilThread {

	// 总票量
	public static int count = 10;

	public static void main(String[] args) {
		statrtMulti();
	}

	public static void statrtMulti() {
		for (int i = 1; i <= 20; i++) {
			TicketRunnable tickrunner = new TicketRunnable();
			Thread thread = new Thread(tickrunner, "Thread No: " + i);
			thread.start();
		}

	}

	public static class TicketRunnable implements Runnable {

		@Override
		public void run() {
			System.out.println(Thread.currentThread().getName() + "  start "
					+ count);
			// TODO Auto-generated method stub
			// logger.info(Thread.currentThread().getName()
			// + "  really  start" + count);
			if (count <= 0) {
				System.out.println(Thread.currentThread().getName()
						+ "  ticket sold out ! No tickets remained!" + count);
				return;
			} else {
				count = count - 1;
				System.out.println(Thread.currentThread().getName()
						+ " bought a ticket,now remaining :" + (count));
			}
		}
	}
}

测试结果，从结果可以看到，票数在不同的线程中已经出现混乱。

Thread No: 2  start 10
Thread No: 6  start 10
Thread No: 4  start 10
Thread No: 5  start 10
Thread No: 3  start 10
Thread No: 9  start 6
Thread No: 1  start 10
Thread No: 1 bought a ticket,now remaining :3
Thread No: 9 bought a ticket,now remaining :4
Thread No: 3 bought a ticket,now remaining :5
Thread No: 12  start 3
Thread No: 5 bought a ticket,now remaining :6
Thread No: 4 bought a ticket,now remaining :7
Thread No: 8  start 7
Thread No: 7  start 8
Thread No: 12 bought a ticket,now remaining :1
Thread No: 14  start 0
Thread No: 6 bought a ticket,now remaining :8
Thread No: 16  start 0
Thread No: 2 bought a ticket,now remaining :9
Thread No: 16  ticket sold out ! No tickets remained!0
Thread No: 14  ticket sold ou