有什么方法可以从字符串生成相同的 UUID

Question

我想知道是否有办法根据String. 生成相同的 UUID 我用 UUID 试过了，好像没有这个功能。

Answer 1

UUID.nameUUIDFromBytes() 方法生成 MD5 UUID。 SHA1 优于 MD5，如果向后兼容性不是问题。

这是一个生成 MD5 和 SHA1 UUID 的实用程序类。它还支持 UUID.nameUUIDFromBytes() 方法不支持的命名空间，尽管 RFC-4122 要求。随意使用和分享。

package your.package.name;

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).
 *
 */
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) + "'");
    }
}

这是输出：

// 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'

您还可以使用uuid-creator 库。看这个例子：

// Create a name based UUID (SHA1)
String name = "JUST_A_TEST_STRING";
UUID uuid = UuidCreator.getNameBasedSha1(name);

项目页面：https://github.com/f4b6a3/uuid-creator

Answer 2

您应该使用 UUID v5。

第 3 版和第 5 版 UUID 是通过对命名空间标识符和名称进行散列生成的。版本 3 使用 MD5 作为散列算法，版本 5 使用 SHA-1.1 - wikipedia

UUID v5 需要一个命名空间。该命名空间应该是一个 UUID v4，您可以使用 generate online。命名空间确保对于给定的输入，输出总是相同的。

可以找到 UUID v5 的可能实现 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>

可以这样使用：

UUID namespace = ; // todo generate a UUID v4.
String input = "input";
UUID uuid = UuidCreator.getNameBasedSha1(namespace, input);

（在某种程度上，对于随机数生成器，命名空间就像种子一样。相比之下，虽然种子应该是随机的，但我们的命名空间是一个常数。这迫使我们的生成器总是为给定的输入产生相同的值。）

Answer 3

如果您正在寻找 Javascript 替代方案，请查看 uuid-by-string，它还提供了使用 SHA-1 或 MD5 哈希函数的选项。

Answer 4

您可以通过这种方式使用 UUID 为您的输入字符串获取始终相同的 UUID：

 String aString="JUST_A_TEST_STRING";
 String result = UUID.nameUUIDFromBytes(aString.getBytes()).toString();