com.litongjava.tio.utils.snowflake.SnowflakeIdGenerator Maven / Gradle / Ivy
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t-io is a aio framework for java
package com.litongjava.tio.utils.snowflake;
public class SnowflakeIdGenerator {
// 起始的时间戳，可以设置为程序开始运行的时间或者其他固定值
private static final long START_TIMESTAMP = 1625076000000L; // 2021-07-01 00:00:00
// 每个部分占用的位数
private static final long SEQUENCE_BITS = 12; // 序列号占用的位数
private static final long WORKER_ID_BITS = 5; // 工作机器ID占用的位数
private static final long DATACENTER_ID_BITS = 5; // 数据中心ID占用的位数
// 每个部分的最大值
private static final long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BITS);
private static final long MAX_WORKER_ID = -1L ^ (-1L << WORKER_ID_BITS);
private static final long MAX_DATACENTER_ID = -1L ^ (-1L << DATACENTER_ID_BITS);
// 每个部分向左的位移
private static final long WORKER_ID_SHIFT = SEQUENCE_BITS;
private static final long DATACENTER_ID_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS;
private static final long TIMESTAMP_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS + DATACENTER_ID_BITS;
// 工作机器ID和数据中心ID
private long workerId;
private long datacenterId;
// 序列号和上次生成ID的时间戳
private long sequence = 0L;
private long lastTimestamp = -1L;
public SnowflakeIdGenerator(long workerId, long datacenterId) {
if (workerId > MAX_WORKER_ID || workerId < 0) {
throw new IllegalArgumentException("Worker ID can't be greater than " + MAX_WORKER_ID + " or less than 0");
}
if (datacenterId > MAX_DATACENTER_ID || datacenterId < 0) {
throw new IllegalArgumentException(
"Datacenter ID can't be greater than " + MAX_DATACENTER_ID + " or less than 0");
}
this.workerId = workerId;
this.datacenterId = datacenterId;
}
public synchronized long generateId() {
long currentTimestamp = getTimestamp();
if (currentTimestamp < lastTimestamp) {
throw new RuntimeException("Clock moved backwards. Refusing to generate ID");
}
if (currentTimestamp == lastTimestamp) {
sequence = (sequence + 1) & MAX_SEQUENCE;
if (sequence == 0) {
// 当前毫秒的序列号已经达到最大值，等待下一毫秒
currentTimestamp = getNextTimestamp(lastTimestamp);
}
} else {
sequence = 0L;
}
lastTimestamp = currentTimestamp;
return (currentTimestamp - START_TIMESTAMP) << TIMESTAMP_SHIFT | datacenterId << DATACENTER_ID_SHIFT
| workerId << WORKER_ID_SHIFT | sequence;
}
private long getNextTimestamp(long lastTimestamp) {
long currentTimestamp = getTimestamp();
while (currentTimestamp <= lastTimestamp) {
currentTimestamp = getTimestamp();
}
return currentTimestamp;
}
private long getTimestamp() {
return System.currentTimeMillis();
}
}