Help to create an extension to encrypt un a256gcm

Hi, I need help to create an extension capable of encoding in rsa-oaep-256 in a256gcm like this website: Online JWT tool and Using JSON Web Encryption (JWE) - DZone
there are many examples in java, but I have not been able to find any of them useful for the extension.

Using asymmetric encryption like RSA and symmetric encryption like AES-GCM are 2 totally different ways of encrypting and decrypting. You could use 2 extensions, one for RSA and the other for AES-GCM.

AES-GCM extension
RSA extension