Generating GUID/UUID in Apex

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Guides, or Globally Unique Identifiers, are 128-bit numbers used to identify information in computer systems. In Apex, generating a GUID/UUID can be achieved through various methods. This article will provide an overview of the different approaches, including built-in methods and custom implementations.

Built-in Method (Spring '24 and later)

Starting from Spring '24, Salesforce provides a built-in UUID class with a method to generate random UUIDs.

• Use the UUID.randomUUID() method to generate a random UUID instance.
• Convert the UUID instance to a string using the toString() method.

UUID uuIdV4 = UUID.randomUUID();
String uuIdV4Str = UUID.randomUUID().toString();

Custom Implementation

For versions prior to Spring '24, you can use a custom implementation to generate a GUID/UUID.

Using Crypto.generateAESKey()

One approach is to use the Crypto.generateAESKey() method to generate a random 128-bit key, which can be converted to a hexadecimal string and formatted as a GUID/UUID.

Blob b = Crypto.generateAESKey(128);
String h = EncodingUtil.convertToHex(b);
String guid = h.substring(0, 8) + '-' + h.substring(8, 12) + '-' + h.substring(12, 16) + '-' + h.substring(16, 20) + '-' + h.substring(20);

Using GuidUtil Class

Another approach is to create a custom GuidUtil class that generates a GUID/UUID using a cryptographically secure random number generator.

public class GuidUtil {
    private static List<String> hexMap = new List<String> {
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
    };

    public static String NewGuid() {
        // Generate 128 random bits
        String randomStringAsHex = EncodingUtil.convertToHex(Crypto.generateAESKey(128));

        // Set the version and variant
        String versionHexBits = randomStringAsHex.substring(14, 16);
        String variantHexBits = randomStringAsHex.substring(18, 20);

        Integer versionIntBits = convertHexToInt(versionHexBits);
        Integer variantIntBits = convertHexToInt(variantHexBits);

        Integer versionShiftedIntBits = versionIntBits & 15 | 64;
        Integer variantShiftedIntBits = variantIntBits & 63 | 128;

        String versionShiftedHexBits = convertIntToHex(versionShiftedIntBits);
        String variantShiftedHexBits = convertIntToHex(variantShiftedIntBits);

        // Format the GUID/UUID
        String guid = randomStringAsHex.substring(0, 8) + '-' + randomStringAsHex.substring(8, 12) + '-' + versionShiftedHexBits + randomStringAsHex.substring(14, 16) + '-' + variantShiftedHexBits + randomStringAsHex.substring(18, 20) + '-' + randomStringAsHex.substring(20);

        return guid;
    }

    static Integer convertHexToInt(String hex) {
        Integer d0 = hexMap.indexOf(hex.substring(1, 2));
        Integer d1 = hexMap.indexOf(hex.substring(0, 1));
        Integer intval = d0 + (d1 * 16);
        return intval;
    }

    static String convertIntToHex(Integer intval) {
        String hs0 = hexMap.get(intval & 15);
        String hs1 = hexMap.get(((intval >> 4) & 15));
        return hs1 + hs0;
    }
}

Comparison of Methods

In conclusion, generating a GUID/UUID in Apex can be achieved through various methods, including built-in and custom implementations. The choice of method depends on the specific requirements and security needs of your application.

Example Use Cases

• Generating a unique identifier for a record in a custom object
• Creating a random key for encryption purposes
• Identifying a unique session or user

Best Practices

• Use the built-in UUID class (Spring '24 and later) for simplicity and security
• Use a custom implementation with a cryptographically secure random number generator for high-security requirements
• Avoid using Math.random() for generating GUID/UUIDs due to its lack of security and uniqueness guarantees

Further Reading

• Salesforce Documentation: UUID Class
• Salesforce Documentation: Crypto Class
• Stack Overflow: Generating a GUID/UUID in Apex