diff --git a/CHANGELOG.md b/CHANGELOG.md
index bc4cb1a7b..e82677009 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@
### 🐣新特性
* 【core 】 CopyOptions支持以Lambda方式设置忽略属性列表（pr#590@Gitee）
* 【core 】 增加中文姓名正则及其校验（pr#592@Gitee）
+* 【core 】 Snowflake支持sequence使用随机数（issue#I51EJY@Gitee）
### 🐞Bug修复
* 【core 】 修复UserAgentUtil识别Linux出错（issue#I50YGY@Gitee）
diff --git a/hutool-core/src/main/java/cn/hutool/core/lang/Snowflake.java b/hutool-core/src/main/java/cn/hutool/core/lang/Snowflake.java
index 1ba75e310..c9eeac826 100644
--- a/hutool-core/src/main/java/cn/hutool/core/lang/Snowflake.java
+++ b/hutool-core/src/main/java/cn/hutool/core/lang/Snowflake.java
@@ -2,6 +2,7 @@ package cn.hutool.core.lang;
import cn.hutool.core.date.SystemClock;
import cn.hutool.core.util.IdUtil;
+import cn.hutool.core.util.RandomUtil;
import cn.hutool.core.util.StrUtil;
import java.io.Serializable;
@@ -61,16 +62,30 @@ public class Snowflake implements Serializable {
// 时间毫秒数左移22位
private static final long TIMESTAMP_LEFT_SHIFT = SEQUENCE_BITS + WORKER_ID_BITS + DATA_CENTER_ID_BITS;
// 序列掩码，用于限定序列最大值不能超过4095
- @SuppressWarnings("FieldCanBeLocal")
private static final long SEQUENCE_MASK = ~(-1L << SEQUENCE_BITS);// 4095
+ /**
+ * 初始化时间点
+ */
private final long twepoch;
private final long workerId;
private final long dataCenterId;
private final boolean useSystemClock;
- // 允许的时钟回拨数
+ /**
+ * 允许的时钟回拨毫秒数
+ */
private final long timeOffset;
+ /**
+ * 当在低频模式下时，序号始终为0，导致生成ID始终为偶数
+ * 此属性用于限定一个随机上限，在不同毫秒下生成序号时，给定一个随机数，避免偶数问题。
+ * 注意次数必须小于{@link #SEQUENCE_MASK}，{@code 0}表示不使用随机数。
+ * 这个上限不包括值本身。
+ */
+ private final long randomSequenceLimit;
+ /**
+ * 自增序号，当高频模式下时，同一毫秒内生成N个ID，则这个序号在同一毫秒下，自增以避免ID重复。
+ */
private long sequence = 0L;
private long lastTimestamp = -1L;
@@ -84,7 +99,7 @@ public class Snowflake implements Serializable {
/**
* 构造
*
- * @param workerId 终端ID
+ * @param workerId 终端ID
*/
public Snowflake(long workerId) {
this(workerId, IdUtil.getDataCenterId(MAX_DATA_CENTER_ID));
@@ -127,26 +142,30 @@ public class Snowflake implements Serializable {
* @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
- * @param timeOffset 允许时间回拨的毫秒数
- * @since 5.7.3
+ * @param timeOffset 允许时间回拨的毫秒数
+ * @since 5.8.0
*/
public Snowflake(Date epochDate, long workerId, long dataCenterId, boolean isUseSystemClock, long timeOffset) {
- if (null != epochDate) {
- this.twepoch = epochDate.getTime();
- } else{
- // Thu, 04 Nov 2010 01:42:54 GMT
- this.twepoch = DEFAULT_TWEPOCH;
- }
- if (workerId > MAX_WORKER_ID || workerId < 0) {
- throw new IllegalArgumentException(StrUtil.format("worker Id can't be greater than {} or less than 0", MAX_WORKER_ID));
- }
- if (dataCenterId > MAX_DATA_CENTER_ID || dataCenterId < 0) {
- throw new IllegalArgumentException(StrUtil.format("datacenter Id can't be greater than {} or less than 0", MAX_DATA_CENTER_ID));
- }
- this.workerId = workerId;
- this.dataCenterId = dataCenterId;
+ this(epochDate, workerId, dataCenterId, isUseSystemClock, timeOffset, 0);
+ }
+
+ /**
+ * @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
+ * @param timeOffset 允许时间回拨的毫秒数
+ * @param randomSequenceLimit 限定一个随机上限，在不同毫秒下生成序号时，给定一个随机数，避免偶数问题，0表示无随机，上限不包括值本身。
+ * @since 5.8.0
+ */
+ public Snowflake(Date epochDate, long workerId, long dataCenterId,
+ boolean isUseSystemClock, long timeOffset, long randomSequenceLimit) {
+ this.twepoch = (null != epochDate) ? epochDate.getTime() : DEFAULT_TWEPOCH;
+ this.workerId = Assert.checkBetween(workerId, 0, MAX_WORKER_ID);
+ this.dataCenterId = Assert.checkBetween(dataCenterId, 0, MAX_DATA_CENTER_ID);
this.useSystemClock = isUseSystemClock;
this.timeOffset = timeOffset;
+ this.randomSequenceLimit = Assert.checkBetween(randomSequenceLimit, 0, SEQUENCE_MASK);
}
/**
@@ -187,10 +206,10 @@ public class Snowflake implements Serializable {
public synchronized long nextId() {
long timestamp = genTime();
if (timestamp < this.lastTimestamp) {
- if(this.lastTimestamp - timestamp < timeOffset){
+ if (this.lastTimestamp - timestamp < timeOffset) {
// 容忍指定的回拨，避免NTP校时造成的异常
timestamp = lastTimestamp;
- } else{
+ } else {
// 如果服务器时间有问题(时钟后退) 报错。
throw new IllegalStateException(StrUtil.format("Clock moved backwards. Refusing to generate id for {}ms", lastTimestamp - timestamp));
}
@@ -203,7 +222,12 @@ public class Snowflake implements Serializable {
}
this.sequence = sequence;
} else {
- sequence = 0L;
+ // issue#I51EJY
+ if (randomSequenceLimit > 1) {
+ sequence = RandomUtil.randomLong(randomSequenceLimit);
+ } else {
+ sequence = 0L;
+ }
}
lastTimestamp = timestamp;
diff --git a/hutool-core/src/test/java/cn/hutool/core/lang/SnowflakeTest.java b/hutool-core/src/test/java/cn/hutool/core/lang/SnowflakeTest.java
index f41512233..ca02e5e67 100644
--- a/hutool-core/src/test/java/cn/hutool/core/lang/SnowflakeTest.java
+++ b/hutool-core/src/test/java/cn/hutool/core/lang/SnowflakeTest.java
@@ -59,7 +59,7 @@ public class SnowflakeTest {
Set ids = new ConcurrentHashSet<>();
ThreadUtil.concurrencyTest(100, () -> {
- for (int i = 0; i < 5000; i++) {
+ for (int i = 0; i < 50000; i++) {
if(false == ids.add(snowflake.nextId())){
throw new UtilException("重复ID！");
}
@@ -74,4 +74,33 @@ public class SnowflakeTest {
Assert.assertEquals(19, StrUtil.toString(l).length());
}
}
+
+ @Test
+ @Ignore
+ public void snowflakeRandomSequenceTest(){
+ final Snowflake snowflake = new Snowflake(null, 0, 0,
+ false, Snowflake.DEFAULT_TIME_OFFSET, 2);
+ for (int i = 0; i < 1000; i++) {
+ final long id = snowflake.nextId();
+ Console.log(id);
+ ThreadUtil.sleep(10);
+ }
+ }
+
+ @Test
+ @Ignore
+ public void uniqueOfRandomSequenceTest(){
+ // 测试并发环境下生成ID是否重复
+ final Snowflake snowflake = new Snowflake(null, 0, 0,
+ false, Snowflake.DEFAULT_TIME_OFFSET, 100);
+
+ Set ids = new ConcurrentHashSet<>();
+ ThreadUtil.concurrencyTest(100, () -> {
+ for (int i = 0; i < 50000; i++) {
+ if(false == ids.add(snowflake.nextId())){
+ throw new UtilException("重复ID！");
+ }
+ }
+ });
+ }
}