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Twitter_Snowflake-Twitter雪花算法加长使用年限-Java版
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| /** | |
| * Twitter_Snowflake加长使用年限Java版 | |
| * <pre> | |
| * 此版本在原版的基础上将10位数据机器位分一半增加到时间戳位组成46位时间戳数据位。 | |
| * 相对原版来说优点是延长使用时间到2000多年，缺点是最大只能部署32个节点，适合访问量不大的系统。 | |
| * 修改后的结构如下(每部分用-分开): | |
| * | |
| * 0 - 0000000000 0000000000 0000000000 0000000000 00000 0 - 00000 - 00000 00000 00 | |
| * | |
| * 1位标识，由于long基本类型在Java中是带符号的，最高位是符号位，正数是0，负数是1，所以id一般是正数，最高位是0 | |
| * | |
| * 46位时间截(毫秒级)，注意，46位时间截不是存储当前时间的时间截，而是存储时间截的差值（当前时间截 - 开始时间截)得到的值）， | |
| * 这里的的开始时间截，一般是我们的id生成器开始使用的时间，由我们程序来指定的（如下下面程序SnowflakeIdWorker类的idepoch属性）。 | |
| * | |
| * 46位的时间截，可以使用2231年，年T = (1L << 46) / (1000L * 60 * 60 * 24 * 365) = 2231 | |
| * 5位的数据机器位，可以部署在32个节点 | |
| * 12位序列，毫秒内的计数，12位的计数顺序号支持每个节点每毫秒(同一机器，同一时间截)产生4096个ID序号 | |
| * 加起来刚好64位，为一个Long型。 | |
| * | |
| * SnowFlake的优点是，整体上按照时间自增排序，并且整个分布式系统内不会产生ID碰撞(由数据中心ID和机器ID作区分)，并且效率较高。 | |
| * | |
| * from https://gist.github.com/sudot/76010fcd4d9e617c80cbce76f28a93cb | |
| * thanks https://github.com/twitter/snowflake/blob/scala_28/src/main/scala/com/twitter/service/snowflake/IdWorker.scala | |
| * </pre> | |
| * | |
| * @author tangjialin on 2018-08-27. | |
| */ | |
| public class SnowflakeIdLongTerm { | |
| /** 机器id所占的位数 */ | |
| private static final long WORKER_ID_BITS = 5L; | |
| /** 支持的最大机器id，结果是31 (这个移位算法可以很快的计算出几位二进制数所能表示的最大十进制数) */ | |
| public static final long MAX_WORKER_ID = ~(-1L << WORKER_ID_BITS); | |
| /** 序列在id中占的位数 */ | |
| private static final long SEQUENCE_BITS = 12L; | |
| /** 机器ID向左移12位 */ | |
| private static final long WORKER_ID_SHIFT = SEQUENCE_BITS; | |
| /** 时间截向左移17位(5+12) */ | |
| private static final long TIMESTAMP_LEFT_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS; | |
| /** 生成序列的掩码，这里为4095 (0b111111111111=0xfff=4095) */ | |
| private static final long SEQUENCE_MASK = ~(-1L << SEQUENCE_BITS); | |
| /** | |
| * 开始时间截 (2025-10-01)一旦使用不可改变 | |
| * <br/> | |
| * 生成方式: | |
| * <br/> | |
| * System.out.println(new SimpleDateFormat("yyyy-MM-dd").parse("2025-10-01").getTime()); | |
| */ | |
| private final long idEpoch = 1759248000000L; | |
| /** 工作机器ID(0~31) */ | |
| private final long workerId; | |
| /** 上次生成ID的时间截 */ | |
| private long lastTimestamp = -1L; | |
| /** 毫秒内序列(0~4095) */ | |
| private long sequence = 0L; | |
| private static final int initWorkerId = 0; | |
| public SnowflakeIdLongTerm() { | |
| this(initWorkerId); | |
| } | |
| /** | |
| * 构造函数 | |
| * | |
| * @param workerId 工作ID (0~31) | |
| */ | |
| public SnowflakeIdLongTerm(long workerId) { | |
| this.workerId = workerId; | |
| if (workerId < 0 || workerId > MAX_WORKER_ID) { | |
| throw new IllegalArgumentException("workerId is illegal: " + workerId); | |
| } | |
| if (idEpoch >= System.currentTimeMillis()) { | |
| throw new IllegalArgumentException("idEpoch is illegal: " + idEpoch); | |
| } | |
| } | |
| public long getWorkerId() { | |
| return workerId; | |
| } | |
| public long getTime() { | |
| return System.currentTimeMillis(); | |
| } | |
| public long getId() { | |
| return nextId(); | |
| } | |
| public String getStringId() { | |
| return Long.toString(nextId()); | |
| } | |
| /** | |
| * 获得下一个ID (该方法是线程安全的) | |
| * | |
| * @return SnowflakeId | |
| */ | |
| private synchronized long nextId() { | |
| long timestamp = timeGen(); | |
| if (timestamp < lastTimestamp) { | |
| throw new IllegalStateException("Clock moved backwards."); | |
| } | |
| if (lastTimestamp == timestamp) { | |
| sequence = (sequence + 1) & SEQUENCE_MASK; | |
| if (sequence == 0) { | |
| timestamp = tilNextMillis(lastTimestamp); | |
| } | |
| } else { | |
| sequence = 0; | |
| } | |
| lastTimestamp = timestamp; | |
| return ((timestamp - idEpoch) << TIMESTAMP_LEFT_SHIFT) | |
| | (workerId << WORKER_ID_SHIFT) | |
| | sequence; | |
| } | |
| /** | |
| * 获取id的时间戳(millis秒) | |
| * | |
| * @param id 通过{@link SnowflakeIdLongTerm#nextId()}生成的id值 | |
| * @return id的时间戳(millis秒) | |
| */ | |
| public long getIdTimestamp(long id) { | |
| return idEpoch + (id >> TIMESTAMP_LEFT_SHIFT); | |
| } | |
| /** | |
| * 阻塞到下一个毫秒，直到获得新的时间戳 | |
| * | |
| * @param lastTimestamp 上次生成ID的时间截 | |
| * @return 当前时间戳 | |
| */ | |
| private long tilNextMillis(long lastTimestamp) { | |
| long timestamp = timeGen(); | |
| while (timestamp <= lastTimestamp) { | |
| timestamp = timeGen(); | |
| } | |
| return timestamp; | |
| } | |
| /** | |
| * 返回以毫秒为单位的当前时间 | |
| * | |
| * @return 当前时间(毫秒) | |
| */ | |
| private long timeGen() { | |
| return System.currentTimeMillis(); | |
| } | |
| @Override | |
| public String toString() { | |
| final StringBuilder sb = new StringBuilder("SnowflakeIdWorker{"); | |
| sb.append("workerId=").append(workerId); | |
| sb.append(", idEpoch=").append(idEpoch); | |
| sb.append(", lastTimestamp=").append(lastTimestamp); | |
| sb.append(", sequence=").append(sequence); | |
| sb.append('}'); | |
| return sb.toString(); | |
| } | |
| } |
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