| New file |
| | |
| | | package com.xiaopeng.common.core.utils; |
| | | |
| | | /** |
| | | * see @https://raw.githubusercontent.com/beyondfengyu/SnowFlake/master/SnowFlake.java |
| | | * Created by Lox on 2017/8/21. |
| | | */ |
| | | public class SnowFlake { |
| | | /** |
| | | * 起始的时间戳 |
| | | */ |
| | | private static long START_STMP = 1503305692631L; |
| | | |
| | | /** |
| | | * 每一部分占用的位数 |
| | | */ |
| | | private final static long SEQUENCE_BIT = 12; //序列号占用的位数 |
| | | private final static long MACHINE_BIT = 5; //机器标识占用的位数 |
| | | private final static long DATACENTER_BIT = 5;//数据中心占用的位数 |
| | | |
| | | /** |
| | | * 每一部分的最大值 |
| | | */ |
| | | public final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT); |
| | | public final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT); |
| | | private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT); |
| | | |
| | | /** |
| | | * 每一部分向左的位移 |
| | | */ |
| | | private final static long MACHINE_LEFT = SEQUENCE_BIT; |
| | | private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT; |
| | | private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT; |
| | | |
| | | private long datacenterId; //数据中心 |
| | | private long machineId; //机器标识 |
| | | private long sequence = 0L; //序列号 |
| | | private long lastStmp = -1L;//上一次时间戳 |
| | | |
| | | public SnowFlake(long datacenterId, long machineId) { |
| | | if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) { |
| | | throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0"); |
| | | } |
| | | if (machineId > MAX_MACHINE_NUM || machineId < 0) { |
| | | throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0"); |
| | | } |
| | | this.datacenterId = datacenterId; |
| | | this.machineId = machineId; |
| | | } |
| | | |
| | | /** |
| | | * 设置初始时间,各业务方的旧算法有可能初始时间不一致,请使用 |
| | | * @param timestamp 设定的新初始时间戳 |
| | | * @return 当前对象 |
| | | */ |
| | | public SnowFlake withStartTimestamp(long timestamp) { |
| | | SnowFlake.START_STMP = timestamp; |
| | | return this; |
| | | } |
| | | |
| | | /** |
| | | * 产生下一个ID |
| | | * |
| | | * @return |
| | | */ |
| | | public synchronized long nextId() { |
| | | long currStmp = getNewstmp(); |
| | | if (currStmp < lastStmp) { |
| | | throw new RuntimeException("Clock moved backwards. Refusing to generate id"); |
| | | } |
| | | |
| | | if (currStmp == lastStmp) { |
| | | //相同毫秒内,序列号自增 |
| | | sequence = (sequence + 1) & MAX_SEQUENCE; |
| | | //同一毫秒的序列数已经达到最大 |
| | | if (sequence == 0L) { |
| | | currStmp = getNextMill(); |
| | | } |
| | | } else { |
| | | //不同毫秒内,序列号置为0 |
| | | sequence = 0L; |
| | | } |
| | | |
| | | lastStmp = currStmp; |
| | | |
| | | return (currStmp - START_STMP) << TIMESTMP_LEFT //时间戳部分 |
| | | | datacenterId << DATACENTER_LEFT //数据中心部分 |
| | | | machineId << MACHINE_LEFT //机器标识部分 |
| | | | sequence; //序列号部分 |
| | | } |
| | | |
| | | private long getNextMill() { |
| | | long mill = getNewstmp(); |
| | | while (mill <= lastStmp) { |
| | | mill = getNewstmp(); |
| | | } |
| | | return mill; |
| | | } |
| | | |
| | | private long getNewstmp() { |
| | | return System.currentTimeMillis(); |
| | | } |
| | | |
| | | // public static void main(String[] args) { |
| | | // SnowFlake snowFlake = new SnowFlake(0, 0); |
| | | // snowFlake.withStartTimestamp(1420041600000L); |
| | | // |
| | | // for (int i = 0; i < (1 << 5); i++) { |
| | | // System.out.println(snowFlake.nextId()); |
| | | // } |
| | | // } |
| | | } |