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101 lines
3.3 KiB
101 lines
3.3 KiB
package com.ynxbd.common.helper.common;
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/**
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* @author wsq
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* @description 雪花算法
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* @date 2019/8/14 下午8:22
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*/
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public class SnowHelper {
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/**
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* 起始的时间戳
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*/
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private final static long START_STAMP = 3500522218L;
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/**
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* 每一部分占用的位数
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*/
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private final static long SEQUENCE_BIT = 12; // 序列号占用的位数
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private final static long MACHINE_BIT = 5; // 机器标识占用的位数
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private final static long DATACENTER_BIT = 5; // 数据中心占用的位数
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/**
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* 每一部分的最大值
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*/
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private final static long MAX_DATACENTER_NUM = ~(-1L << DATACENTER_BIT);
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private final static long MAX_MACHINE_NUM = ~(-1L << MACHINE_BIT);
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private final static long MAX_SEQUENCE = ~(-1L << SEQUENCE_BIT);
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/**
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* 每一部分向左的位移
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*/
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private final static long MACHINE_LEFT = SEQUENCE_BIT;
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private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
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private final static long TIME_STAMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;
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private long datacenterId; // 数据中心
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private long machineId; // 机器标识
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private long sequence = 0L; // 序列号
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private long lastStamp = -1L; // 上一次时间戳
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public SnowHelper(long datacenterId, long machineId) {
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if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
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throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");
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}
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if (machineId > MAX_MACHINE_NUM || machineId < 0) {
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throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
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}
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this.datacenterId = datacenterId;
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this.machineId = machineId;
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}
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/**
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* 产生下一个ID
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*
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*/
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public synchronized long nextId() {
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long curTimeStamp = getCurTime();
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if (curTimeStamp < lastStamp) {
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throw new RuntimeException("Clock moved backwards. Refusing to generate id");
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}
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if (curTimeStamp == lastStamp) {
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//相同毫秒内，序列号自增
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sequence = (sequence + 1) & MAX_SEQUENCE;
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//同一毫秒的序列数已经达到最大
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if (sequence == 0L) {
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curTimeStamp = getNextMill();
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}
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} else {
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//不同毫秒内，序列号置为0
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sequence = 0L;
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}
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lastStamp = curTimeStamp;
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return (curTimeStamp - START_STAMP) << TIME_STAMP_LEFT //时间戳部分
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| datacenterId << DATACENTER_LEFT //数据中心部分
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| machineId << MACHINE_LEFT //机器标识部分
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| sequence; //序列号部分
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}
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private long getNextMill() {
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long mill = getCurTime();
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while (mill <= lastStamp) {
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mill = getCurTime();
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}
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return mill;
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}
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private long getCurTime() {
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return System.currentTimeMillis();
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}
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public static void main(String[] args) {
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SnowHelper snowFlake = new SnowHelper(2, 3);
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for (int i = 0; i < (1 << 12); i++) {
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System.out.println(snowFlake.nextId());
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}
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}
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} |