本文参考:http://www.blogjava.net/stevenjohn/archive/2015/05/17/425127.html?utm_source=tuicool
SnowflakeIdHelper.java:
package com.xy6.snowflake;
import java.util.Date;
public final class SnowflakeIdHelper {
private static long workerId = 0;
private static long datacenterId = 0;
private static SnowflakeIdWorker idWorker = new SnowflakeIdWorker(workerId, datacenterId);
private SnowflakeIdHelper() {
}
public static SnowflakeIdWorker getSnowflakeIdWorker() {
return idWorker;
}
public static long generateId() {
return idWorker.nextId();
}
public static String generateStrId() {
return idWorker.nextId() + "";
}
public static long getTimestampValue(long id) {
long twepoch = SnowflakeIdWorker.twepoch;
long time = id >> 22;
return time + twepoch;
}
public static Date getTimestamp(long id) {
return new Date(getTimestampValue(id));
}
public static long getGenerateIdStart(Date date) {
long sequence = 0L;
long workerIdBits = 5L;
long datacenterIdBits = 5L;
long sequenceBits = 12L;
long workerIdShift = sequenceBits;
long datacenterIdShift = sequenceBits + workerIdBits;
long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
long twepoch = SnowflakeIdWorker.twepoch;
long timestamp = date.getTime();
return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
}
public static long getDatacenterId() {
return datacenterId;
}
public void setDatacenterId(long datacenterId) {
SnowflakeIdHelper.datacenterId = datacenterId;
}
public static long getWorkerId() {
return workerId;
}
public void setWorkerId(long workerId) {
SnowflakeIdHelper.workerId = workerId;
}
/**
* 初始化方法
*/
public static void init(long workerId, long datacenterId) {
SnowflakeIdHelper.workerId = workerId;
SnowflakeIdHelper.datacenterId = datacenterId;
idWorker = new SnowflakeIdWorker(workerId, datacenterId);
}
/**
* 初始化方法
*/
public void init() {
idWorker = new SnowflakeIdWorker(workerId, datacenterId);
}
}
SnowflakeIdWorker.java:
package com.xy6.snowflake;
import java.util.Random;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class SnowflakeIdWorker {
protected static final Logger LOG = LoggerFactory.getLogger(SnowflakeIdWorker.class);
private long workerId;
private long datacenterId;
private long sequence = 0L;
/** 2015-01-01 00:00:00 */
// public static long twepoch = 1420041600000L;
public static long twepoch = 1288834974657L;
private long workerIdBits = 5L;
private long datacenterIdBits = 5L;
private long maxWorkerId = -1L ^ (-1L << workerIdBits);
private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
private long sequenceBits = 12L;
private long workerIdShift = sequenceBits;
private long datacenterIdShift = sequenceBits + workerIdBits;
private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
private long sequenceMask = -1L ^ (-1L << sequenceBits);
private long lastTimestamp = -1L;
private Random r = new Random();
public SnowflakeIdWorker(long workerId, long datacenterId) {
// sanity check for workerId
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;
LOG.info(String.format("worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d", timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, workerId));
}
public synchronized long nextId() {
long timestamp = timeGen();
if (timestamp < lastTimestamp) {
LOG.error(String.format("clock is moving backwards. Rejecting requests until %d.", lastTimestamp));
throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
}
if (lastTimestamp == timestamp) {
sequence = (sequence + 1) & sequenceMask;
if (sequence == 0) {
timestamp = tilNextMillis(lastTimestamp);
}
} else {
// sequence = 0L;
sequence = r.nextInt(2);
}
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 System.currentTimeMillis();
}
}
用法:
package com.xy6.snowflake;
public class Demo2 {
public static void main(String[] args) {
// 716908940310347777
System.err.println(SnowflakeIdHelper.generateId());
}
}