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/**<p>项目名：</p>
* <p>包名： com.zdb.module.test</p>
* <p>文件名：IdWorker.java</p>
* <p>版本信息：</p>
* <p>日期：2015-5-23-下午1:17:49</p>
* Copyright (c) 2015singno公司-版权所有
*/
package com.zdb.module.test;
/**<p>名称：IdWorker.java</p>
* <p>描述：分布式自增长ID</p>
* <pre>
* Twitter的 Snowflake JAVA实现方案
* </pre>
* @author 鲍建明
* @date 2015-5-23 下午1:17:49
* @version 1.0.0
*/
public class IdWorker {
private final long workerId;
private final static long twepoch = 1288834974657L;
private long sequence = 0L;
private final static long workerIdBits = 4L;
public final static long maxWorkerId = -1L ^ -1L << workerIdBits;
private final static long sequenceBits = 10L;
private final static long workerIdShift = sequenceBits;
private final static long timestampLeftShift = sequenceBits + workerIdBits;
public final static long sequenceMask = -1L ^ -1L << sequenceBits;
private long lastTimestamp = -1L;
public IdWorker(final long workerId) {
super();
if (workerId > this.maxWorkerId || workerId < 0) {
throw new IllegalArgumentException(String.format(
"worker Id can‘t be greater than %d or less than 0",
this.maxWorkerId));
}
this.workerId = workerId;
}
public synchronized long nextId() {
long timestamp = this.timeGen();
if (this.lastTimestamp == timestamp) {
this.sequence = (this.sequence + 1) & this.sequenceMask;
if (this.sequence == 0) {
System.out.println("###########" + sequenceMask);
timestamp = this.tilNextMillis(this.lastTimestamp);
}
} else {
this.sequence = 0;
}
if (timestamp < this.lastTimestamp) {
try {
throw new Exception(
String.format(
"Clock moved backwards. Refusing to generate id for %d milliseconds",
this.lastTimestamp - timestamp));
} catch (Exception e) {
e.printStackTrace();
}
}
this.lastTimestamp = timestamp;
long nextId = ((timestamp - twepoch << timestampLeftShift))
| (this.workerId << this.workerIdShift) | (this.sequence);
System.out.println("timestamp:" + timestamp + ",timestampLeftShift:"
+ timestampLeftShift + ",nextId:" + nextId + ",workerId:"
+ workerId + ",sequence:" + sequence);
return nextId;
}
private long tilNextMillis(final long lastTimestamp) {
long timestamp = this.timeGen();
while (timestamp <= lastTimestamp) {
timestamp = this.timeGen();
}
return timestamp;
}
private long timeGen() {
return System.currentTimeMillis();
}
public static void main(String[] args){
IdWorker worker2 = new IdWorker(2);
System.out.println(worker2.nextId());
}
}
分布式自增长ID(Twitter的 Snowflake JAVA实现方案 )
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原文地址：http://my.oschina.net/u/1995545/blog/418891
