public class Sequence { /** * 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; /** * 机器标识位数 */ private final long workerIdBits = 3L; private final long datacenterIdBits = 3L; private final long maxWorkerId = -1L ^ (-1L << workerIdBits); private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits); /** * 毫秒内自增位 */ private final long sequenceBits = 9L; 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; /** * 0,并发控制 */ private long sequence = 0L; /** * 上次生产id时间戳 */ private long lastTimestamp = -1L; public Sequence() { this.datacenterId = getDatacenterId(maxDatacenterId); this.workerId = getMaxWorkerId(datacenterId, maxWorkerId); } /** * @param workerId * 工作机器ID * @param datacenterId * 序列号 */ public Sequence(long workerId, long datacenterId) { if (workerId > maxWorkerId || workerId < 0) { throw new MyRuntimeException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId)); } if (datacenterId > maxDatacenterId || datacenterId < 0) { throw new MyRuntimeException( String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId)); } this.workerId = workerId; this.datacenterId = datacenterId; } /** * 获取下一个ID * * @return */ public synchronized long nextId() { long timestamp = timeGen(); if (timestamp < lastTimestamp) { throw new MyRuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp)); } if (lastTimestamp == timestamp) { sequence = (sequence + 1) & sequenceMask; if (sequence == 0) { timestamp = tilNextMillis(lastTimestamp); } } else { sequence = 0L; } lastTimestamp = timestamp; return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence; } protected long tilNextMillis(long lastTimestamp) { long timestamp = timeGen(); while (timestamp <= lastTimestamp) { timestamp = timeGen(); } return timestamp; } protected long timeGen() { return SystemClock.now(); } /** * <p> * 获取 maxWorkerId * </p> */ protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) { StringBuffer mpid = new StringBuffer(); mpid.append(datacenterId); String name = ManagementFactory.getRuntimeMXBean().getName(); if (StringUtils.isNotEmpty(name)) { /* * GET jvmPid */ mpid.append(name.split("@")[0]); } /* * MAC + PID 的 hashcode 获取16个低位 */ return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1); } /** * <p> * 数据标识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) { } return id; } }
nextId方法产生id,主要是orcle数据库中使用
原文地址:http://www.cnblogs.com/wlm-boke/p/16792164.html
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