com.github.hugh.id.Snowflake Maven / Gradle / Ivy
package com.github.hugh.id;
import com.github.hugh.util.DateUtils;
import com.github.hugh.util.EmptyUtils;
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.HashMap;
import java.util.Map;
/**
* 雪花算法
*
* Created: 2019/3
* [理解分布式id生成算法SnowFlake](https://segmentfault.com/a/1190000011282426?utm_source=tag-newest)
*
* @author hugh
* @since 1.0.2
*/
public class Snowflake {
/**
* 起始的时间戳
*/
private static final long START_STMP = 1288834974657L;
/**
* 每一部分占用的位数
*/
private static final long SEQUENCE_BIT = 12; // 序列号占用的位数
private static final long MACHINE_BIT = 5; // 机器标识占用的位数
private static final long DATA_CENTER_BIT = 5;// 数据中心占用的位数
/**
* 每一部分的最大值
*/
private static final long MAX_DATA_CENTER_NUM = ~(-1L << DATA_CENTER_BIT);
private static final long MAX_MACHINE_NUM = ~(-1L << MACHINE_BIT);
private static final long MAX_SEQUENCE = ~(-1L << SEQUENCE_BIT);
/**
* 每一部分向左的位移
*/
private static final long MACHINE_LEFT = SEQUENCE_BIT;
private static final long DATA_CENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
private static final long TIMESTMP_LEFT = DATA_CENTER_LEFT + DATA_CENTER_BIT;
private long dataCenterId; // 数据中心
private long machineId; // 机器标识
private long sequence = 0L; // 序列号
private long lastStmp = -1L;// 上一次时间戳
public Snowflake() {
this.dataCenterId = getDataCenterId(MAX_DATA_CENTER_NUM);
this.machineId = getMaxWorkerId(dataCenterId, MAX_MACHINE_NUM);
}
/**
* @param machineId 工作机器ID
* @param dataCenterId 序列号
*/
public Snowflake(long dataCenterId, long machineId) {
if (dataCenterId > MAX_DATA_CENTER_NUM || dataCenterId < 0) {
throw new IllegalArgumentException("dataCenterId can't be greater than MAX_DATA_CENTER_NUM or less than 0");
}
if (machineId > MAX_MACHINE_NUM || machineId < 0) {
throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
}
this.dataCenterId = dataCenterId;
this.machineId = machineId;
}
/**
* 获取 maxWorkerId
*
* @param dataCenterId 客户端编号
* @param maxWorkerId 机器标识
* @return 最大机器标识
*/
protected static long getMaxWorkerId(long dataCenterId, long maxWorkerId) {
StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append(dataCenterId);
String name = ManagementFactory.getRuntimeMXBean().getName();
if (EmptyUtils.isNotEmpty(name)) {
/*
* GET jvmPid
*/
stringBuilder.append(name.split("@")[0]);
}
/*
* MAC + PID 的 hashcode 获取16个低位
*/
return (stringBuilder.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
}
/**
* 数据标识id部分
*
* @param maxDataCenterId 最大标识
* @return 最大标识
*/
private 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();
if (null != mac) {
id = ((0x000000FF & (long) mac[mac.length - 1]) | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
id = id % (maxDataCenterId + 1);
}
}
} catch (Exception e) {
throw new RuntimeException(e);
}
return id;
}
/**
* 产生下一个ID
*
* @return long
*/
public synchronized long nextId() {
long currStmp = timeGen();
if (currStmp < lastStmp) {
throw new RuntimeException("Clock moved backwards. Refusing to generate id");
}
if (currStmp == lastStmp) {// 相同毫秒内，序列号自增
sequence = (sequence + 1) & MAX_SEQUENCE;
if (sequence == 0L) {// 同一毫秒的序列数已经达到最大
currStmp = getNextMill();
}
} else { // 不同毫秒内，序列号置为0
sequence = 0L;
}
lastStmp = currStmp;
long time = (currStmp - START_STMP) << TIMESTMP_LEFT;// 时间戳部分
return time | dataCenterId << DATA_CENTER_LEFT // 数据中心部分
| machineId << MACHINE_LEFT // 机器标识部分
| sequence; // 序列号部分
}
/**
* 等待直到下一个毫秒
*
* @return 等待直到下一个毫秒
*/
private long getNextMill() {
long mill = timeGen();
while (mill <= lastStmp) {
mill = timeGen();
}
return mill;
}
/**
* 获取时间戳
*
* @return 时间戳
*/
private long timeGen() {
return System.currentTimeMillis();
}
/**
* 通过雪花ID结果。进行解析
* 反解析结果 例：{date=2020-08-28 22:54:30, sequence=146, workerId=30, dataCenter=12}
*
* @param id 雪花ID
* @return Map
*/
public static Map decompile(long id) {
String binaryId = Long.toBinaryString(id);// ID转二进制字符串
int len = binaryId.length();// 长度
int sequenceStart = (int) (len < SEQUENCE_BIT ? 0 : len - SEQUENCE_BIT);
int workerStart = (int) (len < DATA_CENTER_LEFT ? 0 : len - DATA_CENTER_LEFT);
int timeStart = (int) (len < TIMESTMP_LEFT ? 0 : len - TIMESTMP_LEFT);
String sequence = binaryId.substring(sequenceStart, len);// 自增序号
String workerId = sequenceStart == 0 ? "0" : binaryId.substring(workerStart, sequenceStart);
String dataCenterId = workerStart == 0 ? "0" : binaryId.substring(timeStart, workerStart);
String time = timeStart == 0 ? "0" : binaryId.substring(0, timeStart);
Map item = new HashMap<>();
item.put("sequence", Integer.valueOf(sequence, 2));// 二进制转自增ID
item.put("workerId", Integer.valueOf(workerId, 2));// 二进制转机器ID
item.put("dataCenter", Integer.valueOf(dataCenterId, 2));// 二进制转数据中心ID
long diffTime = Long.parseLong(time, 2);// 二进制转long
long timeLong = diffTime + START_STMP;// 加上初初始时间
item.put("date", DateUtils.formatTimestamp(timeLong));
return item;
}
}