Is there any way to generate the same UUID from a String
You can use UUID this way to get always the same UUID for your input String:
String aString="JUST_A_TEST_STRING";
String result = UUID.nameUUIDFromBytes(aString.getBytes()).toString();
The UUID.nameUUIDFromBytes() method generates MD5 UUIDs. SHA1 is preferred over MD5, if backward compatibility is not an issue.
This is a utility class that generates MD5 and SHA1 UUIDs. It also supports namespaces, which the UUID.nameUUIDFromBytes() method does not support, although required by RFC-4122. Feel free to use and share.
package com.example;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.UUID;
/**
* Utility class that creates UUIDv3 (MD5) and UUIDv5 (SHA1).
*
* It is fully compliant with RFC-4122.
*/
public class HashUuidCreator {
// Domain Name System
public static final UUID NAMESPACE_DNS = new UUID(0x6ba7b8109dad11d1L, 0x80b400c04fd430c8L);
// Uniform Resource Locator
public static final UUID NAMESPACE_URL = new UUID(0x6ba7b8119dad11d1L, 0x80b400c04fd430c8L);
// ISO Object ID
public static final UUID NAMESPACE_ISO_OID = new UUID(0x6ba7b8129dad11d1L, 0x80b400c04fd430c8L);
// X.500 Distinguished Name
public static final UUID NAMESPACE_X500_DN = new UUID(0x6ba7b8149dad11d1L, 0x80b400c04fd430c8L);
private static final int VERSION_3 = 3; // UUIDv3 MD5
private static final int VERSION_5 = 5; // UUIDv5 SHA1
private static final String MESSAGE_DIGEST_MD5 = "MD5"; // UUIDv3
private static final String MESSAGE_DIGEST_SHA1 = "SHA-1"; // UUIDv5
private static UUID getHashUuid(UUID namespace, String name, String algorithm, int version) {
final byte[] hash;
final MessageDigest hasher;
try {
// Instantiate a message digest for the chosen algorithm
hasher = MessageDigest.getInstance(algorithm);
// Insert name space if NOT NULL
if (namespace != null) {
hasher.update(toBytes(namespace.getMostSignificantBits()));
hasher.update(toBytes(namespace.getLeastSignificantBits()));
}
// Generate the hash
hash = hasher.digest(name.getBytes(StandardCharsets.UTF_8));
// Split the hash into two parts: MSB and LSB
long msb = toNumber(hash, 0, 8); // first 8 bytes for MSB
long lsb = toNumber(hash, 8, 16); // last 8 bytes for LSB
// Apply version and variant bits (required for RFC-4122 compliance)
msb = (msb & 0xffffffffffff0fffL) | (version & 0x0f) << 12; // apply version bits
lsb = (lsb & 0x3fffffffffffffffL) | 0x8000000000000000L; // apply variant bits
// Return the UUID
return new UUID(msb, lsb);
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException("Message digest algorithm not supported.");
}
}
public static UUID getMd5Uuid(String string) {
return getHashUuid(null, string, MESSAGE_DIGEST_MD5, VERSION_3);
}
public static UUID getSha1Uuid(String string) {
return getHashUuid(null, string, MESSAGE_DIGEST_SHA1, VERSION_5);
}
public static UUID getMd5Uuid(UUID namespace, String string) {
return getHashUuid(namespace, string, MESSAGE_DIGEST_MD5, VERSION_3);
}
public static UUID getSha1Uuid(UUID namespace, String string) {
return getHashUuid(namespace, string, MESSAGE_DIGEST_SHA1, VERSION_5);
}
private static byte[] toBytes(final long number) {
return new byte[] { (byte) (number >>> 56), (byte) (number >>> 48), (byte) (number >>> 40),
(byte) (number >>> 32), (byte) (number >>> 24), (byte) (number >>> 16), (byte) (number >>> 8),
(byte) (number) };
}
private static long toNumber(final byte[] bytes, final int start, final int length) {
long result = 0;
for (int i = start; i < length; i++) {
result = (result << 8) | (bytes[i] & 0xff);
}
return result;
}
/**
* For tests!
*/
public static void main(String[] args) {
String string = "JUST_A_TEST_STRING";
UUID namespace = UUID.randomUUID(); // A custom name space
System.out.println("Java's generator");
System.out.println("UUID.nameUUIDFromBytes(): '" + UUID.nameUUIDFromBytes(string.getBytes()) + "'");
System.out.println();
System.out.println("This generator");
System.out.println("HashUuidCreator.getMd5Uuid(): '" + HashUuidCreator.getMd5Uuid(string) + "'");
System.out.println("HashUuidCreator.getSha1Uuid(): '" + HashUuidCreator.getSha1Uuid(string) + "'");
System.out.println();
System.out.println("This generator WITH name space");
System.out.println("HashUuidCreator.getMd5Uuid(): '" + HashUuidCreator.getMd5Uuid(namespace, string) + "'");
System.out.println("HashUuidCreator.getSha1Uuid(): '" + HashUuidCreator.getSha1Uuid(namespace, string) + "'");
}
}
This is the output:
// Java's generator
UUID.nameUUIDFromBytes(): '9e120341-627f-32be-8393-58b5d655b751'
// This generator
HashUuidCreator.getMd5Uuid(): '9e120341-627f-32be-8393-58b5d655b751'
HashUuidCreator.getSha1Uuid(): 'e4586bed-032a-5ae6-9883-331cd94c4ffa'
// This generator WITH name space (as the standard requires)
HashUuidCreator.getMd5Uuid(): '2b098683-03c9-3ed8-9426-cf5c81ab1f9f'
HashUuidCreator.getSha1Uuid(): '1ef568c7-726b-58cc-a72a-7df173463bbb'
You can also use the uuid-creator library. See this example:
// Create a name based UUID (SHA1)
String name = "JUST_A_TEST_STRING";
UUID uuid = UuidCreator.getNameBasedSha1(name);
Project page: https://github.com/f4b6a3/uuid-creator
You should use UUID v5.
Version-3 and version-5 UUIDs are generated by hashing a namespace identifier and name. Version 3 uses MD5 as the hashing algorithm, and version 5 uses SHA-1.1 - wikipedia
UUID v5 requires a namespace. That namespace should be a UUID v4, which you can just generate online. The namespace assures that for a given input, the output will always be the same.
A possible implementation of UUID v5 can be found here:
<!-- https://search.maven.org/artifact/com.github.f4b6a3/uuid-creator -->
<dependency>
<groupId>com.github.f4b6a3</groupId>
<artifactId>uuid-creator</artifactId>
<version>3.6.0</version>
</dependency>
It can be used as follows:
UUID namespace = ; // todo generate a UUID v4.
String input = "input";
UUID uuid = UuidCreator.getNameBasedSha1(namespace, input);
(In a way, the namespace acts like a seed would, for a random number generator. By contrast, while a seed is supposed to be random, our namespace is a constant. And that forces our generator to always produce the same value for a given input.)
If you are looking for a Javascript alternative, look at uuid-by-string which also gives option to use SHA-1 or MD5 hash functions.