在业务系统中常常需要生成业务流水号，通常可根据流水号判断业务触发时间，同时又必须保证在业务服务多实例情况下流水号的唯一性。网上常见的方案是使用redis自增的功能或直接使用数据库表序列自增功能做流水号，这些方案必须依赖第三方服务使得业务的依赖性变高，可用性降低，基于此是否可开发出不依赖任何第三方服务的流水号功能了？
实现方案再看mybatis-plus源码时，受到生成序列号的实现启发，自己实现了一个订单流水号生成器SequenceNoUtils，分布式订单流水号生成器SequenceNoUtils 基于开源项目：https://gitee.com/yu120/sequence优化改造，使用类雪花算法实现，可生成23个字符串流水号，前15位字符串为时间，具体可到毫秒，后8位为机器ID+序列号，可满足大部分业务场景需求。
订单流水号生成器，最多23个数字字符串，如：22070908371818823233395，15个数字字符时间戳+8个数字字符标识[26位bit(12位机器标识位数(最大4095)+14位序列号(最大16383))， 新的毫秒"sequence"等于1到10000的随机数,16383-10000=6383,故单机排除机器其他性能因数，理论上一秒钟可生成6376617(6383*999)个流水号，4095个业务服务部署，流水号只有在多实例部署下有极低重复，使用时需设置流水号字段做唯一索引，获取重复在获取一次即可。
流水号样例：22071210583016014764553
源码：
package com.likavn.falcon.common.utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.util.Date;
import java.util.concurrent.ThreadLocalRandom;
public class SequenceNoUtils {
private static final Logger logger = LoggerFactory.getLogger(SequenceNoUtils.class);
private static final DateTimeFormatter TIME_FORMATTER = DateTimeFormatter.ofPattern("yyMMddHHmmssSSS");
private final long numberBitsMast = 26L;
private final long workerIdBits = 12L;
private final long sequenceBits = numberBitsMast - workerIdBits;
private final long sequenceMask = ~(-1L << sequenceBits);
private final long workerIdShift = sequenceBits;
private long sequence = 0L;
private long lastTimestamp = -1L;
private final long workerId;
private SequenceNoUtils() {
long maxWorkerId = ~(-1L << workerIdBits);
long dataCenterId = getDataCenterId(~(-1L << 10L));
this.workerId = getMaxWorkerId(dataCenterId, maxWorkerId);
}
public static String generateNo() {
return getSingleton().nextCode();
}
private static SequenceNoUtils getSingleton() {
return SingletonHolder.SINGLETON;
}
private static final class SingletonHolder {
static final SequenceNoUtils SINGLETON = new SequenceNoUtils();
}
private synchronized String nextCode() {
long timestamp = timeGen();
//闰秒
if (timestamp < lastTimestamp) {
long offset = lastTimestamp - timestamp;
if (offset <= 5) {
try {
wait(offset << 1);
timestamp = timeGen();
if (timestamp < lastTimestamp) {
throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));
}
} catch (Exception e) {
throw new RuntimeException(e);
}
} else {
throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));
}
}
if (lastTimestamp == timestamp) {
// 相同毫秒内，序列号自增
sequence = (sequence + 1) & sequenceMask;
if (sequence == 0) {
// 同一毫秒的序列数已经达到最大
timestamp = tilNextMillis(lastTimestamp);
}
} else {
// 新增的毫秒，序列号置为 1 - 10000 随机数
sequence = ThreadLocalRandom.current().nextLong(1, 10000);
}
lastTimestamp = timestamp;
// 时间戳格式化 + (机器标识部分 | 序列号部分)
return TIME_FORMATTER.format(LocalDateTime.ofInstant(new Date(timestamp).toInstant(), ZoneId.systemDefault()))
+ ((workerId << workerIdShift)
| sequence);
}
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 - 2]) | (0x0000FF00 & (((long) mac[mac.length - 1]) << 8))) >> 6;
id = id % (maxDataCenterId + 1);
}
}
} catch (Exception e) {
logger.warn(" getDataCenterId: " + e.getMessage());
}
return id;
}
private static long getMaxWorkerId(long maxDataCenterId, long maxWorkerId) {
StringBuilder mpId = new StringBuilder();
mpId.append(maxDataCenterId);
String name = ManagementFactory.getRuntimeMXBean().getName();
if (null != name && !name.isEmpty()) {
mpId.append(name.split("@")[0]);
}
return (mpId.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
}
private long tilNextMillis(long lastTimestamp) {
long timestamp = timeGen();
while (timestamp <= lastTimestamp) {
timestamp = timeGen();
}
return timestamp;
}
private long timeGen() {
return SystemClock.now();
}
}
使用：
public static void main(String[] args) {
SequenceNoUtils.generateNo()
}
源码地址：SequenceNoUtils
