import java.lang.management.ManagementFactory; import java.net.InetAddress; import java.net.NetworkInterface;//雪花算法代碼實現 public class IdWorker {// 時間起始標記點，作為基準，一般取系統的最近時間（一旦確定不能變動）private final static long twepoch = 1288834974657L;// 機器標識位數private final static long workerIdBits = 5L;// 數據中心標識位數private final static long datacenterIdBits = 5L;// 機器ID最大值private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);// 數據中心ID最大值private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);// 毫秒內自增位private final static long sequenceBits = 12L;// 機器ID偏左移12位private final static long workerIdShift = sequenceBits;// 數據中心ID左移17位private final static long datacenterIdShift = sequenceBits + workerIdBits;// 時間毫秒左移22位private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;private final static long sequenceMask = -1L ^ (-1L << sequenceBits);/* 上次生產id時間戳 */private static long lastTimestamp = -1L;// 0，并發控制private long sequence = 0L;private final long workerId;// 數據標識id部分private final long datacenterId;public IdWorker(){this.datacenterId = getDatacenterId(maxDatacenterId);this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);}/*** @param workerId* 工作機器ID* @param datacenterId* 序列號*/public IdWorker(long workerId, long datacenterId) {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;}/*** 獲取下一個ID** @return*/public synchronized long nextId() {long timestamp = timeGen();if (timestamp < lastTimestamp) {throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));}if (lastTimestamp == timestamp) {// 當前毫秒內，則+1sequence = (sequence + 1) & sequenceMask;if (sequence == 0) {// 當前毫秒內計數滿了，則等待下一秒timestamp = tilNextMillis(lastTimestamp);}} else {sequence = 0L;}lastTimestamp = timestamp;// ID偏移組合生成最終的ID，并返回IDlong nextId = ((timestamp - twepoch) << timestampLeftShift)| (datacenterId << datacenterIdShift)| (workerId << workerIdShift) | 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();}/*** <p>* 獲取 maxWorkerId* </p>*/protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {StringBuffer mpid = new StringBuffer();mpid.append(datacenterId);String name = ManagementFactory.getRuntimeMXBean().getName();if (!name.isEmpty()) {/** GET jvmPid*/mpid.append(name.split("@")[0]);}/** MAC + PID 的 hashcode 獲取16個低位*/return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);}/*** <p>* 數據標識id部分* </p>*/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();id = ((0x000000FF & (long) mac[mac.length - 1])| (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;id = id % (maxDatacenterId + 1);}} catch (Exception e) {System.out.println(" getDatacenterId: " + e.getMessage());}return id;} }

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