redis的分布式锁抢单

原创已于 2023-12-16 23:06:17 修改 · 119 阅读

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文章标签：

#redis #分布式 #数据库

于 2023-12-16 22:43:02 首次发布

本文介绍了如何使用Java编写基于Redis的分布式锁机制，用于模拟抢购场景。通过setnx和delnx方法实现锁的获取和释放，同时展示了如何利用Redisson库进行并发控制。

以下是锁代码


import com.example.demo.conf.RedisUtil;
import redis.clients.jedis.Jedis;

public class lock {
    public static boolean setnx(String key, String val) {
        Jedis jedis = null;
        try {
            jedis = RedisUtil.getJedis();
            if (jedis == null) {
                return false;
            }
            return jedis.set(key, val, "NX", "PX", 1000 * 60).
                    equalsIgnoreCase("ok");
        } catch (Exception ex) {
        } finally {
            if (jedis != null) {
                jedis.close();
            }
        }
        return false;
    }

    public static int delnx(String key, String val) {
        Jedis jedis = null;
        try {
            jedis = RedisUtil.getJedis();
            if (jedis == null) {
                return 0;
            }

            //if redis.call('get','orderkey')=='1111' then return redis.call('del','orderkey') else return 0 end
            StringBuilder sbScript = new StringBuilder();
            sbScript.append("if redis.call('get','").append(key).append("')").append("=='").append(val).append("'").
                    append(" then ").
                    append("    return redis.call('del','").append(key).append("')").
                    append(" else ").
                    append("    return 0").
                    append(" end");

            return Integer.valueOf(jedis.eval(sbScript.toString()).toString());
        } catch (Exception ex) {
        } finally {
            if (jedis != null) {
                jedis.close();
            }
        }
        return 0;
    }
}

下面是抢单代码


import com.example.demo.conf.RedisUtil;
import redis.clients.jedis.Jedis;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;

public class user {
    static Jedis jedis = RedisUtil.getJedis();
    //获取锁的超时时间 秒
    private int timeout = 30 * 1000;

    static final String shangpingKey="phone_key";

    public void qiangdan() {

        //抢到商品的用户
        List<String> shopUsers = new ArrayList<>();

        //构造很多用户
        Vector<String> users = new Vector<>();
        IntStream.range(0, 10000).forEach(b -> {
            users.add("用户-" + b);
        });

        //模拟开抢
        users.parallelStream().forEach(b -> {
            String shopUser = qiang(b);
        });
    }
    /**
     * 模拟抢单动作
     *
     * @param b
     * @return
     */
    private String qiang(String b) {
        //用户开抢时间
        long startTime = System.currentTimeMillis();

        //未抢到的情况下，30秒内继续获取锁
        while ((startTime + timeout) >= System.currentTimeMillis()) {
            if (lock.setnx(shangpingKey, b)) {
                //用户b拿到锁
//                System.out.println("用户"+b+"拿到锁...");
                try {
                    //商品是否剩余
                    int phone = Integer.parseInt(jedis.get("phone"));
                    if (phone <= 0) {
                        break;
                    }


                    jedis.incrBy("phone",-1);


                    String str = b+"抢单成功，所剩库存：" + (phone-1);
                    System.out.println(str);

                } finally {
                    //释放锁
                    lock.delnx(shangpingKey, b);
                }
            } else {
                //
            }
        }
        return "";
    }

    public static void main(String[] args) {
        user user = new user();
        user.qiangdan();
    }
}


        <dependency>
            <groupId>org.redisson</groupId>
            <artifactId>redisson</artifactId>
            <version>3.11.0</version>
        </dependency>

        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
            <version>2.9.0</version>
        </dependency>