Currently ConversionServiceDeducer registers converters and formatters using only the bean instance. This means that we don't consider generics on the method. See https://github.com/spring-projects/spring-boot/issues/24891#issuecomment-818113018 for one example of where this has tripped us up.
We might be able to get the bean definition and call getResolvableType() to obtain the method defined generics. We'd then probably need our own adapters (similar to the ones in GenericConversionService) to expose the method generics.
Comment From: wilkinsona
https://github.com/spring-projects/spring-boot/pull/22885 is a similar sort of problem.
Comment From: philwebb
Thanks @wilkinsona, I was searching for that one and couldn't find it.
Comment From: philwebb