1、新建WorkId類，用于生成工作ID，主要利用ip地址進(jìn)行轉(zhuǎn)換獲得。也可以通過配置文件進(jìn)行配置獲取

package com.hua.common.id;

import org.apache.commons.lang3.RandomUtils;
import org.apache.commons.lang3.StringUtils;

import java.net.Inet4Address;
import java.net.UnknownHostException;

/**
 * @Deacription TODO
 * @Author huazi
 * @Date 2020/4/5 14:29
 **/
public final class WorkId {

    public final static Long generate() {
        try {
            //獲取本地ip地址
            String hostAddress = Inet4Address.getLocalHost().getHostAddress();
            int[] ints = StringUtils.toCodePoints(hostAddress);
            int sums = 0;
            for (int b : ints) {
                sums += b;
            }
            return (long) (sums % 32);
        } catch (UnknownHostException e) {
            // 如果獲取失敗，則使用隨機(jī)數(shù)備用
            return RandomUtils.nextLong(0, 31);
        }
    }
}

2、新建DataCenterId ，用于獲取數(shù)據(jù)中心ID，主要根據(jù)其主機(jī)名稱來(lái)獲取數(shù)據(jù)中心ID。數(shù)據(jù)中心ID也可以從配置文件中設(shè)置

package com.hua.common.id;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.SystemUtils;

/**
 * @Deacription TODO
 * @Author huazi
 * @Date 2020/4/5 14:31
 **/
public final class DataCenterId {

    public final static Long generate() {
 
        int[] ints = StringUtils.toCodePoints(SystemUtils.getHostName());
        int sums = 0;
        for (int i : ints) {
            sums += i;
        }
        return (long) (sums % 32);
    }

}

3、新建Snowflake，雪花算法核心類

package com.hua.common.id;

/**
 * @Deacription TODO
 * @Author huazi
 * @Date 2020/4/5 14:24
 **/
public class Snowflake {

    /**
     * 開始時(shí)間截
     */
    private final long twepoch = 1420041600000L;

    /**
     * 機(jī)器id所占的位數(shù)
     */
    private final long workerIdBits = 5L;

    /**
     * 數(shù)據(jù)標(biāo)識(shí)id所占的位數(shù)
     */
    private final long datacenterIdBits = 5L;

    /**
     *  支持的最大機(jī)器id，結(jié)果是31 (這個(gè)移位算法可以很快的計(jì)算出幾位二進(jìn)制數(shù)所能表示的最大十進(jìn)制數(shù))
     */
    private final long maxWorkerId = -1L ^ (-1L << workerIdBits);

    /**
     *  支持的最大數(shù)據(jù)標(biāo)識(shí)id，結(jié)果是31 
     */
    private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);

    /**
     * 序列在id中占的位數(shù)
     */
    private final long sequenceBits = 12L;

    /**
     * 機(jī)器ID向左移12位
     */
    private final long workerIdShift = sequenceBits;

    /**
     *  數(shù)據(jù)標(biāo)識(shí)id向左移17位(12+5)
     */
    private final long datacenterIdShift = sequenceBits + workerIdBits;

    /**
     * 時(shí)間截向左移22位(5+5+12)
     */
    private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;

    /**
     * 生成序列的掩碼，這里為4095 (0b111111111111=0xfff=4095)
     */
    private final long sequenceMask = -1L ^ (-1L << sequenceBits);

    /**
     * 工作機(jī)器ID(0~31)
     */
    private long workerId;

    /**
     * 數(shù)據(jù)中心ID(0~31)
     */
    private long datacenterId;

    /**
     * 毫秒內(nèi)序列(0~4095)
     */
    private long sequence = 0L;

    /**
     * 上次生成ID的時(shí)間截
     */
    private long lastTimestamp = -1L;


    /**
     * 構(gòu)造函數(shù)
     *
     * @param workerId     工作ID (0~31)
     * @param datacenterId 數(shù)據(jù)中心ID (0~31)
     */
    public Snowflake(long workerId, long datacenterId) {
        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;
    }


    /**
     * 獲得下一個(gè)ID (該方法是線程安全的)
     *
     * @return SnowflakeId
     */
    public synchronized long nextId() {
        long timestamp = currTimeMill();

        //如果當(dāng)前時(shí)間小于上一次ID生成的時(shí)間戳，說(shuō)明系統(tǒng)時(shí)鐘回退過這個(gè)時(shí)候應(yīng)當(dāng)拋出異常
        if (timestamp < lastTimestamp) {
            throw new RuntimeException(
                    String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }

        //如果是同一時(shí)間生成的，則進(jìn)行毫秒內(nèi)序列
        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            //毫秒內(nèi)序列溢出
            if (sequence == 0) {
                //阻塞到下一個(gè)毫秒,獲得新的時(shí)間戳
                timestamp = tilNextMillis(lastTimestamp);
            }
        }
        //時(shí)間戳改變，毫秒內(nèi)序列重置
        else {
            sequence = 0L;
        }

        //上次生成ID的時(shí)間截
        lastTimestamp = timestamp;

        //移位并通過或運(yùn)算拼到一起組成64位的ID
        return ((timestamp - twepoch) << timestampLeftShift)
                | (datacenterId << datacenterIdShift)
                | (workerId << workerIdShift)
                | sequence;
    }

    /**
     * 阻塞到下一個(gè)毫秒，直到獲得新的時(shí)間戳
     *
     * @param lastTimestamp 上次生成ID的時(shí)間截
     * @return 當(dāng)前時(shí)間戳
     */
    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = currTimeMill();
        while (timestamp <= lastTimestamp) {
            timestamp = currTimeMill();
        }
        return timestamp;
    }

   /**
    * 獲取當(dāng)前時(shí)間毫秒值
    **/
    protected long currTimeMill() {
        return System.currentTimeMillis();
    }
}

4、新建SequenceId，用于獲取ID（使用鎖以便其多線程下能夠保證其線程安全）

package com.hua.common.id;

/**
 * @Deacription SequenceId 生成器
 * @Author huazi
 * @Date 2020/4/5 14:28
 **/
public final class SequenceId {

    private static Snowflake SNOW_FLAKE = null;

    
    static {
        Long workId = WorkId.generate();
        Long dataCenterId = DataCenterId.generate();
        SNOW_FLAKE = new Snowflake(workId, dataCenterId);
    }
    /**
    * 加鎖使其多線程下能夠保證其線程安全
    **/
    public synchronized static Long generate() {
        Long id = SNOW_FLAKE.nextId();
        return id;
    }
}