SnowFlakeUtil.java
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package org.nafmii.utils;
import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;
/**
* @description: 雪花算法
* @author: DINGZIYAO
* @date: 2020/9/14 13:59
* @version: v1.0
*/
public class SnowFlakeUtil {
private final static long TWEPOCH = 12888349746579L;
// 机器标识位数
private final static long WORKER_ID_BITS = 5L;
// 数据中心标识位数
private final static long DATACENTER_ID_BITS = 5L;
// 毫秒内自增位数
private final static long SEQUENCE_BITS = 12L;
// 机器ID偏左移12位
private final static long WORKER_ID_SHIFT = SEQUENCE_BITS;
// 数据中心ID左移17位
private final static long DATACENTER_ID_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS;
// 时间毫秒左移22位
private final static long TIMESTAMP_LEFT_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS + DATACENTER_ID_BITS;
//sequence掩码，确保sequnce不会超出上限
private final static long SEQUENCE_MASK = ~(-1L << SEQUENCE_BITS);
//上次时间戳
private static long lastTimestamp = -1L;
//序列
private long sequence = 0L;
//服务器ID
private long workerId = 1L;
private static final long WORKER_MASK = ~(-1L << WORKER_ID_BITS);
//进程编码
private long processId = 1L;
private static final long PROCESS_MASK = ~(-1L << DATACENTER_ID_BITS);
private static SnowFlakeUtil snowFlake = null;
static{
snowFlake = new SnowFlakeUtil();
}
public static synchronized long nextId(){
return snowFlake.getNextId();
}
private SnowFlakeUtil() {
//获取机器编码
this.workerId=this.getMachineNum();
//获取进程编码
RuntimeMXBean runtimeMXBean = ManagementFactory.getRuntimeMXBean();
this.processId= Long.parseLong(runtimeMXBean.getName().split("@")[0]);
//避免编码超出最大值
this.workerId=workerId & WORKER_MASK;
this.processId=processId & PROCESS_MASK;
}
public synchronized long getNextId() {
//获取时间戳
long timestamp = timeGen();
//如果时间戳小于上次时间戳则报错
if (timestamp < lastTimestamp) {
try {
throw new Exception("Clock moved backwards. Refusing to generate id for " + (lastTimestamp - timestamp) + " milliseconds");
} catch (Exception e) {
e.printStackTrace();
}
}
//如果时间戳与上次时间戳相同
if (lastTimestamp == timestamp) {
// 当前毫秒内，则+1，与sequenceMask确保sequence不会超出上限
sequence = (sequence + 1) & SEQUENCE_MASK;
if (sequence == 0) {
// 当前毫秒内计数满了，则等待下一秒
timestamp = tilNextMillis(lastTimestamp);
}
} else {
sequence = 0;
}
lastTimestamp = timestamp;
// ID偏移组合生成最终的ID，并返回ID
long nextId = ((timestamp - TWEPOCH) << TIMESTAMP_LEFT_SHIFT) | (processId << DATACENTER_ID_SHIFT) | (workerId << WORKER_ID_SHIFT) | sequence;
return nextId;
}
/**
* 再次获取时间戳直到获取的时间戳与现有的不同
* @param lastTimestamp
* @return 下一个时间戳
*/
private long tilNextMillis(final long lastTimestamp) {
long timestamp = this.timeGen();
while (timestamp <= lastTimestamp) {
timestamp = this.timeGen();
}
return timestamp;
}
private long timeGen() {
return System.currentTimeMillis();
}
/**
* 获取机器编码
* @return
*/
private long getMachineNum(){
long machinePiece;
StringBuilder sb = new StringBuilder();
Enumeration<NetworkInterface> e = null;
try {
e = NetworkInterface.getNetworkInterfaces();
} catch (SocketException e1) {
e1.printStackTrace();
}
while (e.hasMoreElements()) {
NetworkInterface ni = e.nextElement();
sb.append(ni.toString());
}
machinePiece = sb.toString().hashCode();
return machinePiece;
}
public static void main(String[] args) {
System.out.println(SnowFlakeUtil.nextId());
// 8073480304000524288
// 8073480926335623168
}
}