Intro

In the era of APIs, each resource is identified by unique id. UUID can be used to generate unique id in distributed systems. This article explains how to create base64 unique id based on random UUID.

Generating base64 unique id.

1. First generate UUID using java.util.UUID.randomUUID()
2. Internally uuid is represented as two long integers (2 long = 128 bits) which can be accessed by uuid.getMostSignificantBits()(MSB) and uuid.getLeastSignificantBits() (LSB).
3. Using ByteBuffer create byte[] from MSB and LSB.
4. Using UrlEncoder of Base64 convert byte[] to base64 String.
5. Using substring remove the trailing padding ==.
6. Now, we have base64 string which represents the UUID generated in Step 1.

Code

Following Java code written as spring component. It should be straight forward to use it in other places as well. java.util.Base64 requires Java 8.

package com.sakthipriyan.example;

import java.nio.ByteBuffer;
import java.util.Base64;
import java.util.Base64.Encoder;
import java.util.UUID;

import org.springframework.stereotype.Component;

@Component
public class Uuid {

    private final Encoder encoder;

    public Uuid() {
        this.encoder = Base64.getUrlEncoder();
    }

    public String randomId() {

        // Create random UUID
        UUID uuid = UUID.randomUUID();

        // Create byte[] for base64 from uuid
        byte[] src = ByteBuffer.wrap(new byte[16])
                .putLong(uuid.getMostSignificantBits())
                .putLong(uuid.getLeastSignificantBits())
                .array();

        // Encode to Base64 and remove trailing ==
        return encoder.encodeToString(src).substring(0, 22);
    }

}

Usage

package com.sakthipriyan.example;

@Service
public class ExampleService {

    @Autowired
    private Uuid uuid;

    public void doSomething(){
        String uniqueId = uuid.randomId();
        // Do whatever you want to do.
    }
}

Generated IDs

Base64 IDs generating using uuid.randomId()

Ah2_xI48RWSGwGDcNfbcGQ
eLQuFAB1QRyWY_DHYxUX4Q
oUSCSgEEQCqw1wlGT_kiSw
R_0tJRgqQDGGVT4kXFli_A
SqrVhuCsQlmoiiIn5Pgpiw
FMiXuPLFQwu7yINCqBt-yQ
UQk9E_8ZSaufMhe33Yh6CA
Uj8RweXQRh-Lj5J0CrI5Vw
d8bkw3SeStW-nS7SFMUV4A
-1b351PDTyqaVQ8OhsrAyQ

40% size reduced.

• Hexadecimal uuid f487fbcf-3606-4f35-a23d-5ac3af6de754 generated using UUID.randomUUID().toString() has 36 bytes including the -.
  
• Base64 uuid 9If7zzYGTzWiPVrDr23nVA generated using uuid.randomId() has only 22 bytes.
  
• By using this we can save around 40% of network bytes and storage bytes for unique id.