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Redis唯一ID生成器的实现

Redis 2022-09-21 15:09:04 78

ID的组成部分:

  • 符号位:1bit,永远为0
  • 时间戳:31bit,以秒为单位,可以使用69年
  • 序列号:32bit,秒内的计数器,支持每秒产生2^32个不同ID

生成代码:

public class RedisIdWorker {

  /**
  * 开始时间戳
  */
  private static final long BEGIN_TIMESTAMP = 1640995200L;
  /**
  * 序列号的位数
  */
  private static final int COUNT_BITS = 32;

  private StringRedisTemplate stringRedisTemplate;
  //构造方法形式注入
  public RedisIdWorker(StringRedisTemplate stringRedisTemplate) {
    this.stringRedisTemplate = stringRedisTemplate;
  }

  public long nextId(String keyPrefix){
    //1. 生成时间戳
    LocalDateTime now = LocalDateTime.now();
    long nowSecond = now.toEpochSecond(ZoneOffset.UTC);
    long timestamp = nowSecond - BEGIN_TIMESTAMP;
    //2.生成序列号
    // 2.1 获取当前日期,精确到天
    String date = now.format(DateTimeFormatter.ofPattern("yyyy:MM:dd"));
    long count = stringRedisTemplate.opsForValue().increment("icr:" + keyPrefix + ":" + date);
    //3.拼接并返回

    return timestamp << COUNT_BITS | count;
  }
}

PS:Redis实现全局唯一id生成

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Component;
import org.springframework.util.Assert;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.Calendar;
import java.util.concurrent.TimeUnit;

/**
* 描述:
* 唯一ID生成器
* @author jimmy
* @create 2020-11-06 16:06
*/
@Component
public class GenerateIDUtil {

  @Autowired
  private RedisTemplate redisTemplate;

  /**
  * 生成每天的初始Id
  * @param key
  * @return
  */ public String initPrimaryId(String key) {
    Assert.hasLength(key, "hashName不能为空");
    String hashCol = LocalDate.now().format(DateTimeFormatter.ofPattern("yyyyMMdd"));
    //自定义编号规则
    String hashColVal = hashCol + "00001";
//    redisTemplate.opsForHash().putIfAbsent(hashName, hashCol, hashColVal);

    Long expiresTime = getSecondsNextEarlyMorning();
    redisTemplate.opsForValue().set(key, Long.valueOf(hashColVal), expiresTime, TimeUnit.SECONDS);
    return hashColVal;
  }


  /**
  * 获取分布式Id  
  * @param key
  * @return
  */
  public String getPrimaryId(String key) {

    String id = "";
    if(redisTemplate.hasKey(key)){
      // redisTemplate.opsForValue().get(key);
      // redisTemplate.delete(key);
      id = String.valueOf(redisTemplate.opsForValue().increment(key, 1));
    } else {
      id = initPrimaryId(key);
    }
    return id;
  }


  /**
  * 判断当前时间距离第二天凌晨的秒数
  * @return 返回值单位为[s:秒]
  */
  public Long getSecondsNextEarlyMorning() {
    Calendar cal = Calendar.getInstance();
    cal.add(Calendar.DAY_OF_YEAR, 1);
    cal.set(Calendar.HOUR_OF_DAY, 0);
    cal.set(Calendar.SECOND, 0);
    cal.set(Calendar.MINUTE, 0);
    cal.set(Calendar.MILLISECOND, 0);
    return (cal.getTimeInMillis() - System.currentTimeMillis()) / 1000;
  }
}

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