changeing/sxz-base/src/main/java/com/fdkk/sxz/util/SnowFlakeUUidUtils.java

package com.fdkk.sxz.util;

import com.github.pagehelper.util.StringUtil;
import lombok.extern.log4j.Log4j2;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * 2 * @Author: Abner
 * 3 * @Date: 2020/12/9 16:07
 * 4
 */
@Log4j2
public class SnowFlakeUUidUtils {

    // 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）
    //起始标记点
    private final static long twepoch = 1288834974657L;
    // 机器标识位数
    private final static long workerIdBits = 5L;
    // 数据中心标识位数
    private final static long datacenterIdBits = 5L;
    // 机器ID最大值
    private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);
    // 数据中心ID最大值
    private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
    // 毫秒内自增位
    private final static long sequenceBits = 12L;
    // 机器ID偏左移12位
    private final static long workerIdShift = sequenceBits;
    // 数据中心ID左移17位
    private final static long datacenterIdShift = sequenceBits + workerIdBits;
    // 时间毫秒左移22位
    private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;

    private final static long sequenceMask = -1L ^ (-1L << sequenceBits);

    private final static Lock myLock = new ReentrantLock();
    /* 上次生产id时间戳 */
    private static long lastTimestamp = -1L;
    // 0，并发控制
    private long sequence = 0L;

    private final long workerId;
    // 数据标识id部分
    private final long datacenterId;

    private static volatile SnowFlakeUUidUtils snowFlakeUUidUtils;


    private static SnowFlakeUUidUtils getSingleInstance(Long workerId, Long datacenterId){
        if(null == snowFlakeUUidUtils){
            synchronized (SnowFlakeUUidUtils.class){
                if(null == snowFlakeUUidUtils){
                    if(null != workerId && null != datacenterId){
                        snowFlakeUUidUtils = new SnowFlakeUUidUtils(workerId , datacenterId);
                    }else{
                        snowFlakeUUidUtils = new SnowFlakeUUidUtils();
                    }
                }
            }
        }
        return snowFlakeUUidUtils;
    }

    /**
     * @param workerId 自定义的应用所在的服务器的机器ID，使用默认读取本机则无需传，传个NULL即可
     * @param datacenterId 自定义的应用所在的服务器的数据中心ID，使用默认读取本机则无需传，传个NULL即可
     * @param preStr 自定义的ID前缀
     * **/
    public static String generaUUid(Long workerId, Long datacenterId , String preStr){
        StringBuilder resultId = new StringBuilder();
        SnowFlakeUUidUtils snowFlakeUUidUtils = getSingleInstance(workerId , datacenterId);
        if(StringUtil.isNotEmpty(preStr)){
            return resultId.append(preStr).append(snowFlakeUUidUtils.nextId()).toString();
        }else{
            return resultId.append(snowFlakeUUidUtils.nextId()).toString();
        }
    }

    public SnowFlakeUUidUtils(){
        this.datacenterId = getDatacenterId(maxDatacenterId);
        this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
    }
    /**
     * @param workerId
     *            工作机器ID
     * @param datacenterId
     *            序列号
     */
    public SnowFlakeUUidUtils(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;
    }
    /**
     * 获取下一个ID
     * 线程安全
     * @return NULL 抢锁失败，需要重新调用
     *         数字串 抢锁成功，则生成20位的数字串
     */
    public  Long nextId() {
        try {

            if(myLock.tryLock(700 , TimeUnit.MILLISECONDS)){
                try {
                    long timestamp = timeGen();
                    if (timestamp < lastTimestamp) {
                        throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
                    }

                    if (lastTimestamp == timestamp) {
                        // 当前毫秒内，则+1
                        sequence = (sequence + 1) & sequenceMask;
                        if (sequence == 0) {
                            // 当前毫秒内计数满了，则等待下一秒
                            timestamp = tilNextMillis(lastTimestamp);
                        }
                    } else {
                        sequence = 0L;
                    }
                    lastTimestamp = timestamp;
                    // ID偏移组合生成最终的ID，并返回ID
                    Long nextId = ((timestamp - twepoch) << timestampLeftShift)
                            | (datacenterId << datacenterIdShift)
                            | (workerId << workerIdShift) | sequence;

                    return nextId;
                }catch (Exception e){
                    log.info("生成UUID抢锁失败:{}" , e);
                }finally {
                    myLock.unlock();
                }
            }else{
                return null;
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return null;

    }

    private long tilNextMillis(final long lastTimestamp) {
        long timestamp = this.timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = this.timeGen();
        }
        return timestamp;
    }

    private long timeGen() {
        return System.currentTimeMillis();
    }

    /**
     * <p>
     * 获取 maxWorkerId
     * </p>
     */
    protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
        StringBuffer mpid = new StringBuffer();
        mpid.append(datacenterId);
        String name = ManagementFactory.getRuntimeMXBean().getName();
        if (!name.isEmpty()) {
            /*
             * GET jvmPid
             */
            mpid.append(name.split("@")[0]);
        }
        /*
         * MAC + PID 的 hashcode 获取16个低位
         */
        return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
    }

    /**
     * <p>
     * 数据标识id部分
     * </p>
     */
    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();
                id = ((0x000000FF & (long) mac[mac.length - 1])
                        | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
                id = id % (maxDatacenterId + 1);
            }
        } catch (Exception e) {
            System.out.println(" getDatacenterId: " + e.getMessage());
        }
        return id;
    }

    public static void main(String[] args) {
        for(int i = 0; i < 20; i++){

            System.out.println(SnowFlakeUUidUtils.generaUUid(null, null, null));
        }
    }

}