Spring Reactive xml payload exception java.lang.IllegalStateException: Failed to resolve argument 0 of type 'reactor.core.publisher.Mono'

Question

I have a spring boot application. trying to send xml payload through postman to a Post request. I get the following exception

java.lang.IllegalS         


        

Answer 1

As pointed out by KOrest, Jaxb2XmlDecoder did not implement decodeToMono, but it is now fixed via SPR-16759. So just upgrading to Spring Framework 5.0.6+ / Spring Boot 2.0.2+ should avoid the reported exception.

Side note: like by Brian Clozel, I am not sure of what you try to achieve and you probably should not call subscribe manually but instead return a transformation of the input. doOnNext can be used if you want to print the output without triggering the demand artificially.