OAuth 2.0 Refresh Token (Generic) Regex for Java

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching oauth 2.0 refresh token (generic), ported and verified for Java. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. The snippet below is ready to drop into your Java project — whether you're validating in a Spring Boot controller, a Jakarta EE service, or a standalone utility class.

Java Implementation

// OAuth 2.0 Refresh Token (Generic)
// ReDoS-safe | RegexVault — Security > OAuth & OIDC

import java.util.regex.Pattern;

public class Oauth20RefreshTokenGenericValidator {
    private static final Pattern PATTERN =
        Pattern.compile("^[A-Za-z0-9\\-_.+/=]{40,512}$");

    public static boolean validate(String input) {
        return PATTERN.matcher(input).matches();
    }

    // Example
    public static void main(String[] args) {
        System.out.println(validate("1//0gBcDeFgHiJkLmNoPqRsTuVwXyZ01234567890aBcDeFgHiJkLmNoPqR")); // true
    }
}

Test Cases

When to use this pattern

This pattern is drawn from the Security > OAuth & OIDC category and carries a ReDoS-safe certification. That matters for Java developers because critical in Java applications since the JVM regex engine uses backtracking and is susceptible to ReDoS without careful pattern design. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Refresh tokens are long-lived (hours to years) credentials used to obtain new access tokens. They must be stored securely (not in localStorage or cookies without Secure/HttpOnly flags). Rotation on use (refresh token rotation) is best practice.