Java UUID Compress & Decompress back

Question

I would like to do the following...

a) Compress a generated UUID to String of length 8.

b) Decompress the compressed UUID back to the original UUID.

The reason is because I have to send the UUID to a partnering system, and the partnering system only accepts 8 chars for UUID, and no I cannot request for a change to the partnering system.

So, what is left to do is to compress UUID that I have to 8 char string and then decompress it back to the original UUID when a message is gotten back from the partnering system.

Any ideas?

Thanks.

Answer 1

What you ask is impossible for information-theoretic reasons.

UUIDs as specified by RFC 4122 are 128 bits, as are UUID objects in Java.

Java Strings can store 16 bits per character, which would make for an 8-char string. However, not all bit sequences are valid UTF-16 strings, so in 8 characters you can store fewer than 128 bits of information.

So if you compress a UUID to a valid 8-character string, you have lost information, so in general there's no way to decompress it to retrieve the original UUID back.

What you might have intended is to generate a shorter string to use as a unique identifier. If so, see Generating 8-character only UUIDs.

Answer 2

The best way to achieve url safe uuid compression is to encode it in base64

public class UUIDUtils {

  public static String compress(UUID uuid) {
    ByteBuffer bb = ByteBuffer.allocate(Long.BYTES * 2);
    bb.putLong(uuid.getMostSignificantBits());
    bb.putLong(uuid.getLeastSignificantBits());
    byte[] array = bb.array();
    return Base64.getEncoder().encodeToString(array);
  }

  public static UUID decompress(String compressUUID) {
    ByteBuffer byteBuffer = ByteBuffer.wrap(Base64.getDecoder().decode(compressUUID));
    return new UUID(byteBuffer.getLong(), byteBuffer.getLong());
  }


}

Result: 6227185c-b25b-4497-b821-ba4f8d1fb9a1 -> YicYXLJbRJe4IbpPjR+5oQ==