sql server 雪花Id生成 雪花idc模板

使用时需要在配置文件里面定义

snow-id:
 currentWorkerId: 1
 currentDatacenterId: 1
 currentSequence: 1
import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Component;
 @Component
 //@ConfigurationProperties(prefix = “snow-flake”)
 //@PropertySource(value = {“classpath:/application.yml”}, encoding = “utf-8”)
 public class SnowFlakeGenerateIDUtils {

//因为二进制里第一个 bit 如果是 1，那么都是负数，但是我们生成的 id 都是正数，所以第一个 bit 统一都是 0。

//机器ID  2进制5位  32位减掉1位 31个
private long workerId;
//机房ID 2进制5位  32位减掉1位 31个
private long datacenterId;
//代表一毫秒内生成的多个id的最新序号  12位 4096 -1 = 4095 个
private long sequence;
//设置一个时间初始值    2^41 - 1   差不多可以用69年
private long twepoch = 1585644268888L;
//5位的机器id
private long workerIdBits = 5L;
//5位的机房id
private long datacenterIdBits = 5L;
//每毫秒内产生的id数 2 的 12次方
private long sequenceBits = 12L;
// 这个是二进制运算，就是5 bit最多只能有31个数字，也就是说机器id最多只能是32以内
private long maxWorkerId = -1L ^ (-1L << workerIdBits);
// 这个是一个意思，就是5 bit最多只能有31个数字，机房id最多只能是32以内
private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);

private long workerIdShift = sequenceBits;
private long datacenterIdShift = sequenceBits + workerIdBits;
private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
private long sequenceMask = -1L ^ (-1L << sequenceBits);
//记录产生时间毫秒数，判断是否是同1毫秒
private long lastTimestamp = -1L;
private int count = 1;

public long getWorkerId() {
    return workerId;
}

public long getDatacenterId() {
    return datacenterId;
}

public long getTimestamp() {
    return System.currentTimeMillis();
}

//public static SnowFlakeGenerateIDUtils snowWork = new SnowFlakeGenerateIDUtils(1,1,1);
//用yml注入@value 静态变量赋值行不通
public static long currentWorkerId;//当前机器
public static long currentDatacenterId;//当前机房
public static long currentSequence;//当前序列号
public volatile static SnowFlakeGenerateIDUtils snowWork = null;

public static String getSnowId() {
    //单例，解决并发问题
    if (snowWork == null) {
        synchronized (SnowFlakeGenerateIDUtils.class) {
            if (snowWork == null) {
                snowWork = new SnowFlakeGenerateIDUtils(currentWorkerId, currentDatacenterId, currentSequence);
            }
        }
    }
    Long nextId = snowWork.nextId();
    return nextId.toString();
}

public SnowFlakeGenerateIDUtils() {
}

/***
 * 功能描述: 
 * 〈〉
 * @Param: [workerId:机器ID, datacenterId:机房ID, sequence：序列号]
 * @Return:
 * @Author: by
 * @Date: 2020/5/6 11:45
 */
public SnowFlakeGenerateIDUtils(long workerId, long datacenterId, long sequence) {
    // 检查机房id和机器id是否超过31 不能小于0
    if (workerId > maxWorkerId || workerId < 0) {
        throw new IllegalArgumentException(
                String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
    }

    if (datacenterId > maxDatacenterId || datacenterId < 0) {

        throw new IllegalArgumentException(
                String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
    }
    this.workerId = workerId;
    this.datacenterId = datacenterId;
    this.sequence = sequence;
}

// 这个是核心方法，通过调用nextId()方法，让当前这台机器上的snowflake算法程序生成一个全局唯一的id
public synchronized long nextId() {
    // 这儿就是获取当前时间戳，单位是毫秒
    long timestamp = timeGen();
    if (timestamp < lastTimestamp) {

        System.err.printf(
                "clock is moving backwards. Rejecting requests until %d.", lastTimestamp);
        throw new RuntimeException(
                String.format("Clock moved backwards. Refusing to generate id for %d milliseconds",
                        lastTimestamp - timestamp));
    }

    // 下面是说假设在同一个毫秒内，又发送了一个请求生成一个id
    // 这个时候就得把seqence序号给递增1，最多就是4096
    if (lastTimestamp == timestamp) {

        // 这个意思是说一个毫秒内最多只能有4096个数字，无论你传递多少进来，
        //这个位运算保证始终就是在4096这个范围内，避免你自己传递个sequence超过了4096这个范围
        //4095：111111111111  ==  sequenceMask
        //4096：1000000000000
        //当sequence大于4095，与运算 1000000000000 & 111111111111 =0 0000 0000 0000 0000
        //即sequence =0
        sequence = (sequence + 1) & sequenceMask;
        //System.out.println("同一毫秒:\t" + timestamp + ",生成ID数:\t" + count);
        count++;
        //当某一毫秒的时间，产生的id数 超过4095，系统会进入等待，直到下一毫秒，系统继续产生ID
        if (sequence == 0) {
            timestamp = tilNextMillis(lastTimestamp);
            count = 1;
        }

    } else {
        sequence = 0;
        count = 1;
    }
    // 这儿记录一下最近一次生成id的时间戳，单位是毫秒
    lastTimestamp = timestamp;
    // 这儿就是最核心的二进制位运算操作，生成一个64bit的id
    // 先将当前时间戳左移，放到41 bit那儿；将机房id左移放到5 bit那儿；将机器id左移放到5 bit那儿；将序号放最后12 bit
    // 最后拼接起来成一个64 bit的二进制数字，转换成10进制就是个long型
    return ((timestamp - twepoch) << timestampLeftShift) |
            (datacenterId << datacenterIdShift) |
            (workerId << workerIdShift) | sequence;
}

/**
 * 当某一毫秒的时间，产生的id数 超过4095，系统会进入等待，直到下一毫秒，系统继续产生ID
 *
 * @param lastTimestamp
 * @return
 */
private long tilNextMillis(long lastTimestamp) {

    long timestamp = timeGen();

    while (timestamp <= lastTimestamp) {
        timestamp = timeGen();
    }
    return timestamp;
}

//获取当前时间戳
private long timeGen() {
    return System.currentTimeMillis();
}

public static void main(String[] args) {
    SnowFlakeGenerateIDUtils worker = new SnowFlakeGenerateIDUtils(1, 1, 1);
    for (int i = 0; i < 10; i++) {
        System.out.println(worker.nextId());
    }
}

@Value("${snow-id.currentWorkerId}")
public void setCurrentWorkerId(long currentWorkerId) {
    SnowFlakeGenerateIDUtils.currentWorkerId = currentWorkerId;
}
@Value("${snow-id.currentDatacenterId}")
public void setCurrentDatacenterId(long currentDatacenterId) {
    SnowFlakeGenerateIDUtils.currentDatacenterId = currentDatacenterId;
}
@Value("${snow-id.currentSequence}")
public void setCurrentSequence(long currentSequence) {
    SnowFlakeGenerateIDUtils.currentSequence = currentSequence;
}

}