This is a Java implementation of Universally Unique Lexicographically Sortable Identifier.
In summary:
- Sorted by generation time;
- Can be stored as a UUID/GUID;
- Can be stored as a string of 26 chars;
- Can be stored as an array of 16 bytes;
- String format is encoded to Crockford's base32;
- String format is URL safe, is case insensitive, and has no hyphens.
This project contains a micro benchmark and a good amount of unit tests.
The jar file can be downloaded directly from maven.org.
Read the Javadocs.
Create a ULID:
Ulid ulid = UlidCreator.getUlid();Create a Monotonic ULID:
Ulid ulid = UlidCreator.getMonotonicUlid();Add these lines to your pom.xml.
<!-- https://search.maven.org/artifact/com.github.f4b6a3/ulid-creator -->
<dependency>
<groupId>com.github.f4b6a3</groupId>
<artifactId>ulid-creator</artifactId>
<version>5.2.3</version>
</dependency>See more options in maven.org.
Module and bundle names are the same as the root package name.
- JPMS module name:
com.github.f4b6a3.ulid - OSGi symbolic name:
com.github.f4b6a3.ulid
ULID is a 128-bit identifier. The first 48 bits represent the number of milliseconds since Unix Epoch, 1970-01-01. The remaining 80 bits are generated by a secure random number generator. Its canonical string representation is 26 characters long.
// Generate a ULID
Ulid ulid = UlidCreator.getUlid();Structure of a series of ULIDs:
01EX8Y21KBH49ZZCA7KSKH6X1C
01EX8Y21KBJTFK0JV5J20QPQNR
01EX8Y21KBG2CS1V6WQCTVM7K6
01EX8Y21KB8HPZNBP3PTW7HVEY
01EX8Y21KB3HZV38VAPTPAG1TY
01EX8Y21KB9FTEJHPAGAKYG9Z8
01EX8Y21KBQGKGH2SVPQAYEFFC
01EX8Y21KBY17J9WR9KQR8SE7H
01EX8Y21KCVHYSJGVK4HBXDMR9 < millisecond changed
01EX8Y21KC668W3PEDEAGDHMVG
01EX8Y21KC53D2S5ADQ2EST327
01EX8Y21KCPQ3TENMTY1S7HV56
01EX8Y21KC3755QF9STQEV05EB
01EX8Y21KC5ZSHK908GMDK69WE
01EX8Y21KCSGJS8S1FVS06B3SX
01EX8Y21KC6ZBWQ0JBV337R1CN
^ look
|---------|--------------|
time random
Monotonic ULID is a variant of ULID. The random component is incremented by 1 whenever the current millisecond equals the previous millisecond. Its main advantage is speed.
// Generate a Monotonic ULID
Ulid ulid = UlidCreator.getMonotonicUlid();Structure of a series of Monotonic ULIDs:
01EX8Y7M8MDVX3M3EQG69EEMJW
01EX8Y7M8MDVX3M3EQG69EEMJX
01EX8Y7M8MDVX3M3EQG69EEMJY
01EX8Y7M8MDVX3M3EQG69EEMJZ
01EX8Y7M8MDVX3M3EQG69EEMK0
01EX8Y7M8MDVX3M3EQG69EEMK1
01EX8Y7M8MDVX3M3EQG69EEMK2
01EX8Y7M8MDVX3M3EQG69EEMK3
01EX8Y7M8N1G30CYF2PJR23J2J < millisecond changed
01EX8Y7M8N1G30CYF2PJR23J2K
01EX8Y7M8N1G30CYF2PJR23J2M
01EX8Y7M8N1G30CYF2PJR23J2N
01EX8Y7M8N1G30CYF2PJR23J2P
01EX8Y7M8N1G30CYF2PJR23J2Q
01EX8Y7M8N1G30CYF2PJR23J2R
01EX8Y7M8N1G30CYF2PJR23J2S
^ look ^ look
|---------|--------------|
time random
Hash ULID is a "non-standard" variant of ULID. It always returns the same ULID for a specific pair of arguments. It has the same basic structure as a ULID, except that the random component is replaced with the first 10 bytes of an SHA-256 hash.
// Generate a Hash ULID of a string
long time = file.getCreatedAt();
String name = file.getFileName();
Ulid ulid = UlidCreator.getHashUlid(time, name);// Generate a Hash ULID of a byte array
long time = file.getCreatedAt();
byte[] bytes = file.getFileBinary();
Ulid ulid = UlidCreator.getHashUlid(time, bytes);Structure of Hash ULIDs:
01GZ8AR53SE5XCA1MN1PGCSDJ0
|---------|--------------|
time hash
Create a quick ULID:
Ulid ulid = Ulid.fast();Create a ULID from a canonical string (26 chars):
Ulid ulid = Ulid.from("0123456789ABCDEFGHJKMNPQRS");Convert a ULID into a canonical string in lower case:
String string = ulid.toLowerCase(); // 0123456789abcdefghjkmnpqrsConvert a ULID into a UUID:
UUID uuid = ulid.toUuid(); // 0110c853-1d09-52d8-d73e-1194e95b5f19Convert a ULID into a RFC-4122 UUID v4:
UUID uuid = ulid.toRfc4122().toUuid(); // 0110c853-1d09-42d8-973e-1194e95b5f19
// ^ UUID v4Get the creation instant of a ULID:
Instant instant = ulid.getInstant(); // 2007-02-16T02:13:14.633Z// static method
Instant instant = Ulid.getInstant("0123456789ABCDEFGHJKMNPQRS"); // 2007-02-16T02:13:14.633ZGet only the time component substring:
String ulidTimePart = ulid.toString()
.substring(0, Ulid.TIME_CHARS); // 0123456789Get only the random component substring:
String ulidRandPart = ulid.toString()
.substring(Ulid.TIME_CHARS, Ulid.RANDOM_CHARS); // ABCDEFGHJKMNPQRSInsert a string between the time and random components efficiently (avoiding concatenation) (#29):
String ulidExpanded = new StringBuilder(ulid.toString())
.insert(Ulid.TIME_CHARS, "-INSERTED-")
.toString(); // 0123456789-INSERTED-ABCDEFGHJKMNPQRSA key generator that makes substitution easy if necessary:
package com.example;
import com.github.f4b6a3.ulid.UlidCreator;
public class KeyGenerator {
public static String next() {
return UlidCreator.getUlid().toString();
}
}// use the generator
String key = KeyGenerator.next();A UlidFactory with java.util.Random:
// use a `java.util.Random` instance for fast generation
UlidFactory factory = UlidFactory.newInstance(new Random());// use the factory
Ulid ulid = factory.create();A UlidFactory with RandomGenerator (JDK 17+):
// use a random function that returns a long value
RandomGenerator random = RandomGenerator.getDefault();
UlidFactory factory = UlidFactory.newInstance(() -> random.nextLong());// use the factory
Ulid ulid = factory.create();This section shows benchmarks comparing UlidCreator to UUID.randomUUID().
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THROUGHPUT (operations/msec) Mode Cnt Score Error Units
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UUID_randomUUID thrpt 5 1787,601 ± 489,482 ops/ms ( 1.0)
UUID_randomUUID_toString thrpt 5 1598,467 ± 93,067 ops/ms
- - - - - - - - - - - - - - - - - - - - - - - - - - -
Ulid_fast thrpt 5 100521,737 ±27132,748 ops/ms (56.2)
Ulid_fast_toString thrpt 5 50529,743 ± 8970,574 ops/ms
- - - - - - - - - - - - - - - - - - - - - - - - - - -
UlidCreator_getUlid thrpt 5 2443,810 ± 379,149 ops/ms ( 1.3)
UlidCreator_getUlid_toString thrpt 5 2200,047 ± 539,767 ops/ms
- - - - - - - - - - - - - - - - - - - - - - - - - - -
UlidCreator_getMonotonicUlid thrpt 5 9845,810 ± 1239,148 ops/ms ( 5.5)
UlidCreator_getMonotonicUlid_toString thrpt 5 5748,568 ± 549,121 ops/ms
- - - - - - - - - - - - - - - - - - - - - - - - - - -
UlidCreator_getHashUlid thrpt 5 6651,239 ± 2541,774 ops/ms
UlidCreator_getHashUlidString thrpt 5 6043,582 ± 1879,042 ops/ms
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Total time: 00:03:22
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System: CPU i7-8565U, 16G RAM, Ubuntu 22.04, JVM 11, rng-tools installed.
To execute the benchmark, run ./benchmark/run.sh.
Check out the other ID generators from the same family:
- UUID Creator: Universally Unique Identifiers
- TSID Creator: Time Sortable Identifiers
- KSUID Creator: K-Sortable Globally Unique Identifiers
This library is Open Source software released under the MIT license.