前言
我们经常会遇到这样的场景，需要生成一个唯一的序列号来表明某一个数据的唯一性，在单节点的应用中我们可以简单地使用一个自增的整型来实现实现，但是在分布式情况下这个方式却存在冲突的可能性，那么有什么办法我们可以生成一个唯一的序列号呢，并且如果想使得这个序列号也能展示一些业务信息呢？
正文
UUID实现唯一标识码
UUID 的目的是让分布式系统中的所有元素，都能有唯一的辨识资讯，而不需要透过中央控制端来做辨识资讯的指定。如此一来，每个人都可以建立不与其它人冲突的 UUID(通用唯一标识码)。
UUID的组成：
- 当前日期和时间。
- 时钟序列（数值 按其发生的先后顺序而排列的数列）
- 全局唯一的
IEEE机器识别号。
UUID虽然可以保证全局唯一，但是它占用32位（十进制），而且是无序的，入库时性能比较差。这是因为，关系型数据库的索引都是B+树结构， 如果我们按照ID递增的顺序，新的结点会插入到最后一个结点后面去，当最后一个结点满了，会裂变出新的结点。但如果是插入无序的，不仅会导致中间结点的裂变，还会产生很多不饱和节点，导致性能降低。
UUIDStringUtils：生成UUID唯一标示码的工具类
public class UUIDStringUtils {
public static String randomUUID() {
UUID uuid = UUID.randomUUID();
return uuid.toString().replace("-", "").toUpperCase();
}
}
验证方法
@org.junit.Test
public void test(){
System.out.println("通过UUID的方式生成的唯一序列号"+UUIDStringUtils.randomUUID());
}
运行结果如下：
SnowFlake实现唯一标识码
SnowFlake算法：分布式系统中生成全局唯一且趋势递增的Id.
总共64位2进制，换成十进制为18位
- 第一部分： 1位，始终为0.
- 第二部分：41位，精确为毫秒的时间戳。
- 第三部分：10位，机器码
- 第四部分：12位，序列号
snowflake的优点：
- 是按
ID递增，易于插入到数据库 - 不依赖数据库，在内存中生成，性能好
SnowflakeIdWorker：生成SnowFlake唯一标识码的工具类
public class SnowflakeIdWorker {
// ==============================Fields===========================================
private final long twepoch = 1420041600000L;
private final long workerIdBits = 5L;
private final long datacenterIdBits = 5L;
private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
private final long sequenceBits = 12L;
private final long workerIdShift = sequenceBits;
private final long datacenterIdShift = sequenceBits + workerIdBits;
private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
private final long sequenceMask = -1L ^ (-1L << sequenceBits);
private long workerId;
private long datacenterId;
private long sequence = 0L;
private long lastTimestamp = -1L;
//==============================Constructors=====================================
public SnowflakeIdWorker(long workerId, long datacenterId) {
if (workerId > maxWorkerId || workerId < 0) {
throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
}
if (datacenterId > maxDatacenterId || datacenterId < 0) {
throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
}
this.workerId = workerId;
this.datacenterId = datacenterId;
}
// ==============================Methods==========================================
public synchronized long nextId() {
long timestamp = timeGen();
//如果当前时间小于上一次ID生成的时间戳，说明系统时钟回退过这个时候应当抛出异常
if (timestamp < lastTimestamp) {
throw new RuntimeException(
String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
}
//如果是同一时间生成的，则进行毫秒内序列
if (lastTimestamp == timestamp) {
sequence = (sequence + 1) & sequenceMask;
//毫秒内序列溢出
if (sequence == 0) {
//阻塞到下一个毫秒,获得新的时间戳
timestamp = tilNextMillis(lastTimestamp);
}
}
//时间戳改变，毫秒内序列重置
else {
sequence = 0L;
}
//上次生成ID的时间截
lastTimestamp = timestamp;
//移位并通过或运算拼到一起组成64位的ID
return ((timestamp - twepoch) << timestampLeftShift) //
| (datacenterId << datacenterIdShift) //
| (workerId << workerIdShift) //
| sequence;
}
protected long tilNextMillis(long lastTimestamp) {
long timestamp = timeGen();
while (timestamp <= lastTimestamp) {
timestamp = timeGen();
}
return timestamp;
}
protected long timeGen() {
return System.currentTimeMillis();
}
//==============================Test=============================================
public static void main(String[] args) {
SnowflakeIdWorker idWorker = new SnowflakeIdWorker(0, 0);
for (int i = 0; i < 1000; i++) {
long id = idWorker.nextId();
//转换成二进制
System.out.println(Long.toBinaryString(id));
System.out.println(id);
}
}
}
验证方法
@org.junit.Test
public void test2(){
SnowflakeIdWorker idWorker = new SnowflakeIdWorker(0, 0);
long id = idWorker.nextId();
System.out.println("通过SnowFlake的方式生成的唯一序列号"+Long.toBinaryString(id) );
}
运行结果如下：
通过时间工具生成带有业务标示的唯一标识码
事实上，很多情况下在高并发没有那么多的情况，并且我们需要通过唯一标识码获取一些简单的业务信息时，可以使用Java自带的时间工具类生成一个带有业务标示的唯一标识码。
OrderNoUtils：生成带有业务标示的唯一标识码的工具类
public class OrderNoUtils {
private OrderNoUtils() {
throw new IllegalStateException("Utility class");
}
public static String createOrderNo(String productNo) {
return DateTimeUtils.getTodayChar14() + productNo
+ RandomNumberUtil.createRandomNumber(6);
}
public static String createVipBizNo(String productNo) {
return "VIP" + DateTimeUtils.getTodayChar14() + productNo
+ RandomNumberUtil.createRandomNumber(4);
}
public static String createRequestNo(String identifier,int randomLength) {
return DateTimeUtils.getTodayChar17() + identifier
+ RandomNumberUtil.createRandomNumber(randomLength);
}
}
RandomNumberUtil：生成随机数的工具类
public class RandomNumberUtil {
private RandomNumberUtil() {
}
public static String createRandomNumber(int length) {
StringBuilder strBuffer = new StringBuilder();
Random rd = new Random();
for (int i = 0; i < length; i++) {
strBuffer.append(rd.nextInt(10));
}
return strBuffer.toString();
}
}
DateTimeUtils：时间工具类
public class DateTimeUtils {
// private static Logger logger = LoggerFactory.getLogger(DateTimeUtils.class);
private static List<String> dateFormatPattern = new ArrayList<String>();
private static SimpleDateFormat simpleDateFormat = new SimpleDateFormat();
static {
dateFormatPattern.add("yyyy-MM-dd HH:mm:ss");
dateFormatPattern.add("yyyy-MM-dd HH:mm:ss.S z");
dateFormatPattern.add("yyyy-MM-dd G HH:mm:ss.S z");
dateFormatPattern.add("yyyy-MM-dd HH:mm:ss.S 'UTC'");
dateFormatPattern.add("yyyy-MM-dd G HH:mm:ss.S 'UTC'");
dateFormatPattern.add("yyyy-MM-dd HH:mm:ss.S z");
dateFormatPattern.add("yyyy-MM-dd HH:mm:ss.S a");
dateFormatPattern.add("yyyy-MM-dd HH:mm:ssz");
dateFormatPattern.add("yyyy-MM-dd HH:mm:ss z");
dateFormatPattern.add("yyyy-MM-dd HH:mm:ss 'UTC'");
dateFormatPattern.add("yyyy-MM-dd'T'HH:mm:ss.SX");
dateFormatPattern.add("yyyy-MM-dd'T'HH:mm:ssX");
dateFormatPattern.add("yyyy-MM-dd'T'HH:mmX");
dateFormatPattern.add("yyyy-MM-dd HH:mm:ssa");
dateFormatPattern.add("yyyy/MM/dd");
dateFormatPattern.add("yyyy/M/d");
dateFormatPattern.add("yyyy-MM-dd");
dateFormatPattern.add("yyyy-M-d");
dateFormatPattern.add("yyyy/M/d");
dateFormatPattern.add("yyyy年M月d日");
dateFormatPattern.add("yyyy年MM月dd日");
dateFormatPattern.add("yyyy-MM-dd'T'HH:mm:ss.SSS+0800");
}
// 格式：中文星期
private final static String[] FORMAT_WEEK_CHINESE_SIMPLE = {"周日", "周一", "周二", "周三", "周四", "周五", "周六"};
// 格式：中文星期
private final static String[] FORMAT_WEEK_CHINESE = {"星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六"};
// 格式：英文格式简写
private final static String[] FORMAT_WEEK_ENGLISH_SIMPLE = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
// 格式：英文全称
private final static String[] FORMAT_WEEK_ENGLISH = {"Sun", " Mon", " Tue", " Wed", " Thu", " Fri", " Sat"};
public static String getCurrentYear() {
return DateFormatUtils.format(new Date(), "yyyy");
}
public static String getCurrentMonth() {
return DateFormatUtils.format(new Date(), "MM");
}
public static String getTodayDay() {
return DateFormatUtils.format(new Date(), "dd");
}
public static String getTodayChar6() {
return DateFormatUtils.format(new Date(), "yyyyMM");
}
public static String getTodayChar8() {
return DateFormatUtils.format(new Date(), "yyyyMMdd");
}
public static String getTodayChar12() {
return DateFormatUtils.format(new Date(), "yyyyMMddHHmm");
}
public static String getTodayChar14() {
return DateFormatUtils.format(new Date(), "yyyyMMddHHmmss");
}
public static String getTodayChar17() {
String dateString = DateFormatUtils.format(new Date(), "yyyyMMddHHmmssS");
int length = dateString.length();
if (length < 17) {
String endStr = dateString.substring(14, length);
int len = endStr.length();
for (int i = 0; i < 3 - len; i++) {
endStr = "0" + endStr;
}
dateString = dateString.substring(0, 14) + endStr;
}
return dateString;
}
public static long getSysCurrentTimeMillis() {
return System.currentTimeMillis();
}
public static String convertTimeFormat(long timeMillis, String format) {
return DateFormatUtils.format(timeMillis, format);
}
public static String getSystemTime() {
Calendar theCa = Calendar.getInstance();
theCa.setTime(new Date());
return DateFormatUtils.format(theCa.getTime(), "yyyy-MM-dd HH:mm:ss");
}
public static String getWeekName(int type) {
String strResult = " ";
try {
Calendar calendar = Calendar.getInstance();
int intWeekNum = calendar.get(Calendar.DAY_OF_WEEK);
intWeekNum = intWeekNum - 1;
if (type == 1) {
strResult = FORMAT_WEEK_CHINESE_SIMPLE[intWeekNum];
} else if (type == 2) {
strResult = FORMAT_WEEK_CHINESE[intWeekNum];
} else if (type == 3) {
strResult = FORMAT_WEEK_ENGLISH_SIMPLE[intWeekNum];
} else if (type == 4) {
strResult = FORMAT_WEEK_ENGLISH[intWeekNum];
} else {
strResult = FORMAT_WEEK_CHINESE_SIMPLE[intWeekNum];
}
} catch (Exception ex) {
strResult = " ";
}
return strResult;
}
public static int getCurrentMonthDays() {
Calendar a = Calendar.getInstance();
a.set(Calendar.DATE, 1);// 把日期设置为当月第一天
a.roll(Calendar.DATE, -1);// 日期回滚一天，也就是最后一天
return a.get(Calendar.DATE);
}
public static boolean isBetweenTwoTimes(String startTime, String endTime) {
//当前时间
long nowTime = Long.parseLong(DateFormatUtils.format(new Date(), "yyyyMMddHHmmss"));
if (StringUtils.isBlank(startTime) || StringUtils.isBlank(endTime)) {
return false;
}
if (Long.parseLong(startTime) < nowTime && nowTime < Long.parseLong(endTime)) {
return true;
}
return false;
}
public static boolean isBetweenTwoTimes17(String startTime, String endTime) {
//当前时间
long nowTime = Long.parseLong(DateFormatUtils.format(new Date(), "yyyyMMddHHmmssS"));
if (StringUtils.isBlank(startTime) || StringUtils.isBlank(endTime)) {
return false;
}
if (Long.parseLong(startTime) < nowTime && nowTime < Long.parseLong(endTime)) {
return true;
}
return false;
}
public static long getTodayExpireTime() {
Calendar calendar = Calendar.getInstance();
String date = DateTimeUtils.getTodayChar8();
calendar.set(Calendar.YEAR, Integer.parseInt(date.substring(0, 4)));
calendar.set(Calendar.MONTH, Integer.parseInt(date.substring(4, 6)) - 1);
calendar.set(Calendar.DAY_OF_MONTH, Integer.parseInt(date.substring(6, 8)) + 1);
calendar.set(Calendar.HOUR_OF_DAY, 00);
calendar.set(Calendar.MINUTE, 05);
calendar.set(Calendar.SECOND, 00);
Calendar ccalendar = Calendar.getInstance();// 当前时间
ccalendar.setTime(new Date());
return calendar.getTimeInMillis() - ccalendar.getTimeInMillis();
}
public static long getMonthExpireTime() {
Calendar calendar = Calendar.getInstance();
String date = DateTimeUtils.getTodayChar8();
calendar.set(Calendar.YEAR, Integer.parseInt(date.substring(0, 4)));
calendar.set(Calendar.MONTH, Integer.parseInt(date.substring(4, 6)) - 1);
calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
calendar.set(Calendar.HOUR_OF_DAY, 23);
calendar.set(Calendar.MINUTE, 59);
calendar.set(Calendar.SECOND, 59);
Calendar ccalendar = Calendar.getInstance();// 当前时间
ccalendar.setTime(new Date());
return calendar.getTimeInMillis() - ccalendar.getTimeInMillis();
}
public static long getOneYearExpireTime() {
Calendar calendar = Calendar.getInstance();
String date = DateTimeUtils.getTodayChar8();
calendar.set(Calendar.YEAR, Integer.parseInt(date.substring(0, 4)) + 1);
calendar.set(Calendar.MONTH, Integer.parseInt(date.substring(4, 6)) - 1);
calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
calendar.set(Calendar.HOUR_OF_DAY, 00);
calendar.set(Calendar.MINUTE, 00);
calendar.set(Calendar.SECOND, 00);
Calendar ccalendar = Calendar.getInstance();// 当前时间
ccalendar.setTime(new Date());
return calendar.getTimeInMillis() - ccalendar.getTimeInMillis();
}
public static Date formatDate(String date){
Date result = null;
fp : for (String formatPattern : dateFormatPattern) {
try {
simpleDateFormat.applyPattern(formatPattern);
result = simpleDateFormat.parse(date);
if (result != null) {
break fp;
}
} catch (ParseException e) {
// e.printStackTrace();
//logger.info(date + " format fail");
}
}
return result;
}
}
验证方法
@org.junit.Test
public void test3(){
System.out.println("通过时间工具的方式生成的唯一序列号："+ OrderNoUtils.createOrderNo("13012345678"));
}
运行结果如下：
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