public synchronized String nextId() {
long timestamp = timeGen(); //获取当前毫秒数
//如果服务器时间有问题(时钟后退) 报错。
if (timestamp < lastTimestamp) {
throw new RuntimeException(String.format(
"Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
}
//如果上次生成时间和当前时间相同,在同一毫秒内
if (lastTimestamp == timestamp) {
//sequence自增,因为sequence只有12bit,所以和sequenceMask相与一下,去掉高位
sequence = (sequence + 1) & sequenceMask;
//判断是否溢出,也就是每毫秒内超过4095,当为4096时,与sequenceMask相与,sequence就等于0
if (sequence == 0) {
timestamp = tilNextMillis(lastTimestamp); //自旋等待到下一毫秒
}
} else {
sequence = 0L; //如果和上次生成时间不同,重置sequence,就是下一毫秒开始,sequence计数重新从0开始累加
}
lastTimestamp = timestamp;
long suffix = (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
String datePrefix = DateFormatUtils.format(timestamp, "yyyyMMddHHMMssSSS");
return datePrefix + suffix;
}
protected long tilNextMillis(long lastTimestamp) {
long timestamp = timeGen();
while (timestamp <= lastTimestamp) {
timestamp = timeGen();
}
return timestamp;
}
protected long timeGen() {
return System.currentTimeMillis();
}
private byte getLastIP(){
byte lastip = 0;
try{
InetAddress ip = InetAddress.getLocalHost();
byte[] ipByte = ip.getAddress();
lastip = ipByte[ipByte.length - 1];
} catch (UnknownHostException e) {
e.printStackTrace();
}
return lastip;
}
2022-01-06 12:55:58
2KB
java
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