That HttpServletRequest getRequestURL(); should return protocol based on what kind of connection it is and not based on a incoming http header X-Forwarded-Proto:

Thank you for raising this request! We appreciate your feedback and queries

After reviewing the behavior and the relevant specifications, we’ve concluded that we will not introduce fallback handling when an invalid X-Forwarded-Proto value is provided. While it would be technically possible to attempt to infer the protocol, doing so would introduce security risks and could result in incorrect request handling in certain configurations.

From a security and correctness standpoint, Liberty follows a fail-explicit approach. If a forwarded protocol header is present but invalid, the safest behavior is to treat this as a configuration error rather than attempting to guess the intended protocol. Guessing or silently correcting the value could mask misconfigurations upstream and, in some cases, lead to unintended security implications.

The recommended approach is to ensure that the proxy or front-end server is configured to send a valid and accurate X-Forwarded-Proto value that reflects the actual client connection. Correcting the configuration at that level ensures predictable behavior and avoids ambiguity in request processing.

We understand this may require changes in your proxy or server setup, but this approach aligns with best practices and helps maintain secure and reliable request handling.

Please let us know if you would like assistance validating your current setup or have further questions.
Looking forward to more ideas from you