自定义简化版不重复指定长度随机码生成

Posted 2022-05-19 好大的月亮

前提

业务中经常需要生成一些不重复的随机码，但是又需要指定长度。这就让现成的UUID或者雪花算法生成的id很是捉鸡。

实现

我这边随机码的选择范围是0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ

并且长度指定7位。

我的思路是这样的，既然指定了位数上线，那么肯定是有上限的，62^7就是它的上限了，一般业务一天用不了这么多，一天千万级别就够了。

所以我打算引入 业务编码 + 时间 + 随机码 来组成这个随机码。

业务编码取固定的3位
其中时间，我打算只取后两位，比如2022则只用22，到2099年这个算法也该换了把。然后将时间年月日转成62进制(就是上面的取值范围),可以缩短为3位数.
剩下的4位则用random随机从取值范围数组里取。

代码demo

package com.felix.spring_cloud_one.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.*;
import org.springframework.stereotype.Component;
import org.springframework.util.CollectionUtils;

import java.time.Duration;
import java.time.LocalDateTime;
import java.time.Month;
import java.util.*;
import java.util.concurrent.TimeUnit;

@Component
public class RandomCodeGenerateService 

    @Autowired
    private StringRedisTemplate stringRedisTemplate;


    List<String> list = new ArrayList<>();
    Set<String> set = new HashSet<>();

    static String seed = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    static String[] split = seed.split("");



    public Object randomCodeGenerate(Integer batchSize) 

        LocalDateTime nowStart = LocalDateTime.now();

        LocalDateTime now = LocalDateTime.now();

        int year = now.getYear();

        Month month = now.getMonth();

        int dayOfMonth = now.getDayOfMonth();

        String yearStr = split[Integer.valueOf(String.valueOf(year).substring(2))];
        String monthStr = split[month.getValue()];
        String dayOfMonthStr = split[dayOfMonth];
        String preFix = yearStr + monthStr + dayOfMonthStr;


        //list的key
        String redisKey =  "randomCodeGenerate" + preFix;


        RedisOperations<String, String> operations = stringRedisTemplate.opsForList().getOperations();

        BoundListOperations<String, String> boundListOperations = operations.boundListOps(redisKey);

        Long size = boundListOperations.size();

        List<String> range = boundListOperations.range(0, size);

        Set<String> rangeSet = new HashSet<>(range);

        Set<String> set = randomStr(rangeSet,4, batchSize, preFix);

        ArrayList<String> pushList = new ArrayList<>(set);

        int index = 0;
        int step = 10000;

        int currentIndex = index * step;
        int endIndex = (index + 1) * step;

        //批量保存到redis
        while (endIndex < pushList.size())

            List<String> list = pushList.subList(currentIndex, endIndex);

            boundListOperations.leftPushAll(list.toArray(new String[]));

            index ++;

            currentIndex = index * step;
            endIndex = (index + 1) * step;
        

        if(currentIndex < pushList.size())
            List<String> list = pushList.subList(currentIndex, set.size());
            boundListOperations.leftPushAll(list.toArray(new String[]));
        




        System.out.println("list.size：" + this.list.size());
        System.out.println("set.size：" + this.set.size());

        LocalDateTime nowEnd = LocalDateTime.now();

        Duration duration = Duration.between(nowStart, nowEnd);

        System.out.println("花费了时间" + duration.toMinutes() + "分钟");


        //key过期
        stringRedisTemplate.expire(redisKey, 24, TimeUnit.HOURS);

        return null;
    


    public Set<String> randomStr(Set<String> historySet,int codeLength, int num, String preFix)
        Random random = new Random();
        Set<String> set = new HashSet<>();
        while (set.size() < num)

            String str = "";
            for (int i = 0; i < codeLength; i++) 
                int index = random.nextInt(seed.length());
                str += split[index];
            

            if(!CollectionUtils.isEmpty(historySet) && historySet.contains(str))
                continue;
            

            if(null != preFix)
                str = preFix + str;
            

            set.add(str);
        

        return set;