/** * 自定义 ID 生成器 * ID 生成规则: ID长达 64 bits * * | 41 bits: Timestamp (毫秒) | 3 bits: 区域（机房） | 10 bits: 机器编号 | 10 bits: 序列号 | */ public class GameUUID{ // 基准时间 private long twepoch = 1288834974657L; //Thu, 04 Nov 2010 01:42:54 GMT // 区域标志位数 private final static long regionIdBits = 3L; // 机器标识位数 private final static long workerIdBits = 10L; // 序列号识位数 private final static long sequenceBits = 10L; // 区域标志ID最大值 private final static long maxRegionId = -1L ^ (-1L << regionIdBits); // 机器ID最大值 private final static long maxWorkerId = -1L ^ (-1L << workerIdBits); // 序列号ID最大值 private final static long sequenceMask = -1L ^ (-1L << sequenceBits); // 机器ID偏左移10位 private final static long workerIdShift = sequenceBits; // 业务ID偏左移20位 private final static long regionIdShift = sequenceBits + workerIdBits; // 时间毫秒左移23位 private final static long timestampLeftShift = sequenceBits + workerIdBits + regionIdBits; private static long lastTimestamp = -1L; private long sequence = 0L; private final long workerId; private final long regionId; public GameUUID(long workerId, long regionId) { // 如果超出范围就抛出异常 if (workerId > maxWorkerId || workerId < 0) { throw new IllegalArgumentException("worker Id can't be greater than %d or less than 0"); } if (regionId > maxRegionId || regionId < 0) { throw new IllegalArgumentException("datacenter Id can't be greater than %d or less than 0"); } this.workerId = workerId; this.regionId = regionId; } public GameUUID(long workerId) { // 如果超出范围就抛出异常 if (workerId > maxWorkerId || workerId < 0) { throw new IllegalArgumentException("worker Id can't be greater than %d or less than 0"); } this.workerId = workerId; this.regionId = 0; } public long generate() { return this.nextId(false, 0); } /** * 实际产生代码的 * * @param isPadding * @param busId * @return */ private synchronized long nextId(boolean isPadding, long busId) { long timestamp = timeGen(); long paddingnum = regionId; if (isPadding) { paddingnum = busId; } if (timestamp < lastTimestamp) { try { throw new Exception("Clock moved backwards. Refusing to generate id for " + (lastTimestamp - timestamp) + " milliseconds"); } catch (Exception e) { e.printStackTrace(); } } //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10bit，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1024，当为1024时，与sequenceMask相与，sequence就等于0 if (sequence == 0) { //自旋等待到下一毫秒 timestamp = tailNextMillis(lastTimestamp); } } else { // 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, // 为了保证尾数随机性更大一些,最后一位设置一个随机数 sequence = new SecureRandom().nextInt(10); } lastTimestamp = timestamp; return ((timestamp - twepoch) << timestampLeftShift) | (paddingnum << regionIdShift) | (workerId << workerIdShift) | sequence; } // 防止产生的时间比之前的时间还要小（由于NTP回拨等问题）,保持增量的趋势. private long tailNextMillis(final long lastTimestamp) { long timestamp = this.timeGen(); while (timestamp <= lastTimestamp) { timestamp = this.timeGen(); } return timestamp; } // 获取当前的时间戳 protected long timeGen() { return System.currentTimeMillis(); } } | 
