Encrypt some annotated fields

Hello,
I have some fields annotated with a custom annotation @MyId. It can be applied to single elements (int, strings...) or collections.
My final target is to translate this fields using a custom component (in a web page, I have the key in the session) and I just would like to do this during the JSON serialization.

I cannot find any way to achieve this using GSON (I don't want to write a full custom serializer for each possibile response my backend will send, of course), can you help me?

Thanks
Andrea