/* 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动） */

private final long twepoch = 1288834974657L;

private final long workerIdBits = 5L;/* 机器标识位数 */

private final long datacenterIdBits = 5L;

private final long maxWorkerId = -1L ^ (-1L << workerIdBits);

private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);

private final long sequenceBits = 12L;/* 毫秒内自增位 */

private final long workerIdShift = sequenceBits;

private final long datacenterIdShift = sequenceBits + workerIdBits;

/* 时间戳左移动位 */

private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;

private final long sequenceMask = -1L ^ (-1L << sequenceBits);

private long workerId;

/* 数据标识id部分 */

private long datacenterId;

private long sequence = 0L;/* 0，并发控制 */

private long lastTimestamp = -1L;/* 上次生产id时间戳 */

public Sequence() {

this.datacenterId = getDatacenterId(maxDatacenterId);

this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);

}

/**

public Sequence(long workerId, long datacenterId) {

if (workerId > maxWorkerId || workerId < 0) {

throw new RuntimeException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));

}

if (datacenterId > maxDatacenterId || datacenterId < 0) {

throw new RuntimeException(

String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));

}

this.workerId = workerId;

this.datacenterId = datacenterId;

}

/**

protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {

StringBuilder mpid = new StringBuilder();

mpid.append(datacenterId);

String name = ManagementFactory.getRuntimeMXBean().getName();

if (null != name && !"".equals(name)) {

/*

mpid.append(name.split("@")[0]);

}

/*

return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);

}

/**

protected static long getDatacenterId(long maxDatacenterId) {

long id = 0L;

try {

InetAddress ip = InetAddress.getLocalHost();

NetworkInterface network = NetworkInterface.getByInetAddress(ip);

if (network == null) {

id = 1L;

} else {

byte[] mac = network.getHardwareAddress();

if (null != mac) {

id = ((0x000000FF & (long) mac[mac.length - 1]) | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;

id = id % (maxDatacenterId + 1);

}

}

} catch (Exception e) {

log.warn(" getDatacenterId: " + e.getMessage());

}

return id;

}

/**

public synchronized long nextId() {

long timestamp = timeGen();

if (timestamp < lastTimestamp) {//闰秒

long offset = lastTimestamp - timestamp;

if (offset <= 5) {

try {

wait(offset << 1);

timestamp = timeGen();

if (timestamp < lastTimestamp) {

throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));

}

} catch (Exception e) {

throw new RuntimeException(e);

}

} else {

throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));

}

}

if (lastTimestamp == timestamp) {

// 相同毫秒内，序列号自增

sequence = (sequence + 1) & sequenceMask;

if (sequence == 0) {

// 同一毫秒的序列数已经达到最大

timestamp = tilNextMillis(lastTimestamp);

}

} else {

// 不同毫秒内，序列号置为 1 - 3 随机数

sequence = ThreadLocalRandom.current().nextLong(1, 3);

}

lastTimestamp = timestamp;

return ((timestamp - twepoch) << timestampLeftShift) // 时间戳部分

| (datacenterId << datacenterIdShift) // 数据中心部分

| (workerId << workerIdShift) // 机器标识部分

| sequence; // 序列号部分

}

protected long tilNextMillis(long lastTimestamp) {

long timestamp = timeGen();

while (timestamp <= lastTimestamp) {

timestamp = timeGen();

}

return timestamp;

}

protected long timeGen() {

return SystemClock.now();

}