一個雪花演算法id的生成器，節選自mybatis-plus，苞米豆。

可以再建立一個類，靜態方法。如IdUtils。

package cn.taotao.utils;

/*
 * Copyright (c) 2011-2021, baomidou ([email protected]).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     
 
http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 
 
*/


import com.baomidou.mybatisplus.core.toolkit.Assert;
import com.baomidou.mybatisplus.core.toolkit.StringPool;
import com.baomidou.mybatisplus.core.toolkit.StringUtils;
import com.baomidou.mybatisplus.core.toolkit.SystemClock;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;

 
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.concurrent.ThreadLocalRandom;

/**
 * 分散式高效有序 ID 生產黑科技(sequence)
 *
 * <p>優化開源專案：https://gitee.com/yu120/sequence</p>
 *
 * @author hubin
 * @since 2016-08-18
 */
public class Sequence {

    private static final Log logger = LogFactory.getLog(com.baomidou.mybatisplus.core.toolkit.Sequence.class);
    /**
     * 時間起始標記點，作為基準，一般取系統的最近時間（一旦確定不能變動）
     */
    private final long twepoch = 1288834974657L;
    /**
     * 機器標識位數
     */
    private final long workerIdBits = 5L;
    private final long datacenterIdBits = 5L;
    private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
    private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
    /**
     * 毫秒內自增位
     */
    private final long sequenceBits = 12L;
    private final long workerIdShift = sequenceBits;
    private final long datacenterIdShift = sequenceBits + workerIdBits;
    /**
     * 時間戳左移動位
     */
    private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
    private final long sequenceMask = -1L ^ (-1L << sequenceBits);

    private final long workerId;

    /**
     * 資料標識 ID 部分
     */
    private final long datacenterId;
    /**
     * 併發控制
     */
    private long sequence = 0L;
    /**
     * 上次生產 ID 時間戳
     */
    private long lastTimestamp = -1L;

    public Sequence() {
        this.datacenterId = getDatacenterId(maxDatacenterId);
        this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
    }

    /**
     * 有參構造器
     *
     * @param workerId     工作機器 ID
     * @param datacenterId 序列號
     */
    public Sequence(long workerId, long datacenterId) {
        Assert.isFalse(workerId > maxWorkerId || workerId < 0,
                String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
        Assert.isFalse(datacenterId > maxDatacenterId || datacenterId < 0,
                String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
        this.workerId = workerId;
        this.datacenterId = datacenterId;
    }

    /**
     * 獲取 maxWorkerId
     */
    protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
        StringBuilder mpid = new StringBuilder();
        mpid.append(datacenterId);
        String name = ManagementFactory.getRuntimeMXBean().getName();
        if (StringUtils.isNotBlank(name)) {
            /*
             * GET jvmPid
             */
            mpid.append(name.split(StringPool.AT)[0]);
        }
        /*
         * MAC + PID 的 hashcode 獲取16個低位
         */
        return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
    }

    /**
     * 資料標識id部分
     */
    protected static long getDatacenterId(long maxDatacenterId) {
        long id = 0L;
        try {
            InetAddress ip = InetAddress.getLocalHost();
            NetworkInterface network = NetworkInterface.getByInetAddress(ip);
            if (network == null) {
                id = 1L;
            } else {
                byte[] mac = network.getHardwareAddress();
                if (null != mac) {
                    id = ((0x000000FF & (long) mac[mac.length - 2]) | (0x0000FF00 & (((long) mac[mac.length - 1]) << 8))) >> 6;
                    id = id % (maxDatacenterId + 1);
                }
            }
        } catch (Exception e) {
            logger.warn(" getDatacenterId: " + e.getMessage());
        }
        return id;
    }

    /**
     * 獲取下一個 ID
     *
     * @return 下一個 ID
     */
    public synchronized long nextId() {
        long timestamp = timeGen();
        //閏秒
        if (timestamp < lastTimestamp) {
            long offset = lastTimestamp - timestamp;
            if (offset <= 5) {
                try {
                    wait(offset << 1);
                    timestamp = timeGen();
                    if (timestamp < lastTimestamp) {
                        throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
                    }
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
            } else {
                throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
            }
        }

        if (lastTimestamp == timestamp) {
            // 相同毫秒內，序列號自增
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                // 同一毫秒的序列數已經達到最大
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            // 不同毫秒內，序列號置為 1 - 3 隨機數
            sequence = ThreadLocalRandom.current().nextLong(1, 3);
        }

        lastTimestamp = timestamp;

        // 時間戳部分 | 資料中心部分 | 機器標識部分 | 序列號部分
        return ((timestamp - twepoch) << timestampLeftShift)
                | (datacenterId << datacenterIdShift)
                | (workerId << workerIdShift)
                | sequence;
    }

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

    protected long timeGen() {
        return SystemClock.now();
    }

}

package cn.taotao.utils;

public class IdUtils {

    public static synchronized Long nextId(){
        Sequence sequence = new Sequence();
        return sequence.nextId();
    }
}