* snowflake的结构如下(每部分用-分开):
- *
+ *
*
* 0 - 0000000000 0000000000 0000000000 0000000000 0 - 00000 - 00000 - 000000000000 *- * + *
* 第一位为未使用(符号位表示正数)，接下来的41位为毫秒级时间(41位的长度可以使用69年)
* 然后是5位datacenterId和5位workerId(10位的长度最多支持部署1024个节点）
* 最后12位是毫秒内的计数（12位的计数顺序号支持每个节点每毫秒产生4096个ID序号）
- *
+ *
* 并且可以通过生成的id反推出生成时间,datacenterId和workerId *
* 参考：http://www.cnblogs.com/relucent/p/4955340.html - * + * * @author Looly * @since 3.0.1 */ -public class Snowflake implements Serializable{ +public class Snowflake implements Serializable { private static final long serialVersionUID = 1L; - // Thu, 04 Nov 2010 01:42:54 GMT - private long twepoch = 1288834974657L; + private final long twepoch; private final long workerIdBits = 5L; - private final long datacenterIdBits = 5L; + private final long dataCenterIdBits = 5L; //// 最大支持机器节点数0~31，一共32个 - private final long maxWorkerId = -1L ^ (-1L << workerIdBits); // 最大支持数据中心节点数0~31，一共32个 - private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits); + @SuppressWarnings({"PointlessBitwiseExpression", "FieldCanBeLocal"}) + private final long maxWorkerId = -1L ^ (-1L << workerIdBits); + @SuppressWarnings({"PointlessBitwiseExpression", "FieldCanBeLocal"}) + private final long maxDataCenterId = -1L ^ (-1L << dataCenterIdBits); // 序列号12位 private final long sequenceBits = 12L; // 机器节点左移12位 private final long workerIdShift = sequenceBits; // 数据中心节点左移17位 - private final long datacenterIdShift = sequenceBits + workerIdBits; + private final long dataCenterIdShift = sequenceBits + workerIdBits; // 时间毫秒数左移22位 - private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits; + private final long timestampLeftShift = sequenceBits + workerIdBits + dataCenterIdBits; + @SuppressWarnings({"PointlessBitwiseExpression", "FieldCanBeLocal"}) private final long sequenceMask = -1L ^ (-1L << sequenceBits);// 4095 private long workerId; - private long datacenterId; + private long dataCenterId; private long sequence = 0L; private long lastTimestamp = -1L; private boolean useSystemClock; /** * 构造 - * - * @param workerId 终端ID - * @param datacenterId 数据中心ID + * + * @param workerId 终端ID + * @param dataCenterId 数据中心ID */ - public Snowflake(long workerId, long datacenterId) { - this(workerId, datacenterId, false); + public Snowflake(long workerId, long dataCenterId) { + this(workerId, dataCenterId, false); } /** * 构造 - * - * @param workerId 终端ID - * @param datacenterId 数据中心ID + * + * @param workerId 终端ID + * @param dataCenterId 数据中心ID * @param isUseSystemClock 是否使用{@link SystemClock} 获取当前时间戳 */ - public Snowflake(long workerId, long datacenterId, boolean isUseSystemClock) { + public Snowflake(long workerId, long dataCenterId, boolean isUseSystemClock) { + this(null, workerId, dataCenterId, isUseSystemClock); + } + + /** + * @param epochDate 初始化时间起点（null表示默认起始日期）,后期修改会导致id重复,如果要修改连workerId dataCenterId，慎用 + * @param workerId 工作机器节点id + * @param dataCenterId 数据中心id + * @param isUseSystemClock 是否使用{@link SystemClock} 获取当前时间戳 + * @since 5.1.3 + */ + public Snowflake(Date epochDate, long workerId, long dataCenterId, boolean isUseSystemClock) { + if (null != epochDate) { + this.twepoch = epochDate.getTime(); + } else{ + // Thu, 04 Nov 2010 01:42:54 GMT + this.twepoch = 1288834974657L; + } if (workerId > maxWorkerId || workerId < 0) { throw new IllegalArgumentException(StrUtil.format("worker Id can't be greater than {} or less than 0", maxWorkerId)); } - if (datacenterId > maxDatacenterId || datacenterId < 0) { - throw new IllegalArgumentException(StrUtil.format("datacenter Id can't be greater than {} or less than 0", maxDatacenterId)); + if (dataCenterId > maxDataCenterId || dataCenterId < 0) { + throw new IllegalArgumentException(StrUtil.format("datacenter Id can't be greater than {} or less than 0", maxDataCenterId)); } this.workerId = workerId; - this.datacenterId = datacenterId; + this.dataCenterId = dataCenterId; this.useSystemClock = isUseSystemClock; } - /** - * - * @param epochStr 初始化时间起点 后期修改会导致id重复,如果要修改连workerId datacenterId 一起修改 慎用,格式yyyyMMdd， - * @param workerId 工作机器节点id - * @param datacenterId 数据中心id - * @param isUseSystemClock 是否使用{@link SystemClock} 获取当前时间戳 - */ - public Snowflake(String epochStr, long workerId, long datacenterId, boolean isUseSystemClock) { - this(workerId, datacenterId, isUseSystemClock); - Date d=DateUtil.parse(epochStr, "yyyyMMdd"); - long twepoch=d.getTime(); - if(twepoch>this.twepoch){ - this.twepoch=twepoch; - } - } + /** * 根据Snowflake的ID，获取机器id * @@ -116,11 +120,11 @@ public class Snowflake implements Serializable{ * @return 所属数据中心 */ public long getDataCenterId(long id) { - return id >> datacenterIdShift & ~(-1L << datacenterIdBits); + return id >> dataCenterIdShift & ~(-1L << dataCenterIdBits); } /** - *根据Snowflake的ID，获取生成时间 + * 根据Snowflake的ID，获取生成时间 * * @param id snowflake算法生成的id * @return 生成的时间 @@ -131,7 +135,7 @@ public class Snowflake implements Serializable{ /** * 下一个ID - * + * * @return ID */ public synchronized long nextId() { @@ -151,9 +155,9 @@ public class Snowflake implements Serializable{ lastTimestamp = timestamp; - return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence; + return ((timestamp - twepoch) << timestampLeftShift) | (dataCenterId << dataCenterIdShift) | (workerId << workerIdShift) | sequence; } - + /** * 下一个ID（字符串形式） * @@ -164,9 +168,10 @@ public class Snowflake implements Serializable{ } // ------------------------------------------------------------------------------------------------------------------------------------ Private method start + /** * 循环等待下一个时间 - * + * * @param lastTimestamp 上次记录的时间 * @return 下一个时间 */ @@ -180,7 +185,7 @@ public class Snowflake implements Serializable{ /** * 生成时间戳 - * + * * @return 时间戳 */ private long genTime() {