16:21:15.415 [main] WARN org.springframework.http.converter.json.Jackson2ObjectMapperBuilder - For Jackson Kotlin classes support please add "com.fasterxml.jackson.module:jackson-module-kotlin" to the classpath
It seems we would be able to do some detection on startup and report only once, at least per Jackson2ObjectMapperBuilder initialization.
#20217 Log a warning in Jackson builder when Kotlin is used without jackson-module-kotlin
Is there a reason to put a warning at all? This registerWellKnownModulesIfAvailable method ignores the absences of all other modules completely silently, but puts a warning just for Kotlin. I encountered a situation when I got Kotlin as a transitive dependency, so now I get this warning. The workaround above is probably not desirable for me, because I don't want to do a "general" configuration, I only want to silence this Kotlin warning. I suggest two solutions:
Add a configuration to silence just the Kotlin warning without changing the general config for finding modules
Ignore ClassNotFoundException just like with all the other well-known modules.