com.ck.uuid.Sequence Maven / Gradle / Ivy

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package com.ck.uuid;

import com.ck.tools.Utils;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;


public class Sequence {

    /* 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） */
    private final long twepoch = 1288834974657L;
    private final long workerIdBits = 5L;/* 机器标识位数 */
    private final long datacenterIdBits = 5L;
    private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
    private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
    private final long sequenceBits = 12L;/* 毫秒内自增位 */
    private final long workerIdShift = sequenceBits;
    private final long datacenterIdShift = sequenceBits + workerIdBits;
    /* 时间戳左移动位 */
    private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
    private final long sequenceMask = -1L ^ (-1L << sequenceBits);

    private long workerId;

    /* 数据标识id部分 */
    private long datacenterId;
    private long sequence = 0L;/* 0，并发控制 */
    private long lastTimestamp = -1L;/* 上次生产id时间戳 */

    public Sequence() {
        this.datacenterId = getDatacenterId(maxDatacenterId);
        this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
    }
    /***
     *
     * @param workerId 工作机器ID
     * @param datacenterId 序列号
     */
    public Sequence(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 maxWorkerId
     * @param datacenterId long
     * @param maxWorkerId long
     * @return long
     */
    protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
        StringBuilder mpid = new StringBuilder();
        mpid.append(datacenterId);
        String name = ManagementFactory.getRuntimeMXBean().getName();
        if (Utils.isNull(name)) {
            /*
			 * GET jvmPid
			 */
            mpid.append(name.split("@")[0]);
        }
		/*
		 * MAC + PID 的 hashcode 获取16个低位
		 */
        return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
    }

    /***
     * 数据标识id部分
     * @param maxDatacenterId long
     * @return long
     */
    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) {
            //logger.warn(" getDatacenterId: " + e.getMessage());
            e.printStackTrace();
        }
        return id;
    }

    /***
     * 获取下一个ID
     * @return long
     */
    public synchronized long nextId() {
        long timestamp = timeGen();
        if (timestamp < lastTimestamp) {//闰秒
            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) {
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }

        lastTimestamp = timestamp;

        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();
    }


    public static void main(String[] args) {
        System.out.println("开始："+System.currentTimeMillis());
        for (int i = 0; i < 50; i++) {
            long id =IdWorker.getId();
            System.out.println(id);
//            System.out.println(Long.toBinaryString(id));
        }
        System.out.println("结束："+System.currentTimeMillis());
    }

}