Avoid multiple warnings related to jackson-module-kotlin in Jackson2ObjectMapperBuilder [SPR-16497]

[spring-projects-issues]

Rossen Stoyanchev opened SPR-16497 and commented

The following message appears repeatedly:

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.

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Affects: 5.0.3

Issue Links:

• #20217 Log a warning in Jackson builder when Kotlin is used without jackson-module-kotlin

Referenced from: commits 7baf33f

[mauhiz]

For people who reach this page wondering how to silence the warn:

  @Bean
  fun configureJackson2() = Jackson2ObjectMapperBuilderCustomizer { it.findModulesViaServiceLoader(true) }

[metaruslan]

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:

1. Add a configuration to silence just the Kotlin warning without changing the general config for finding modules
2. Ignore ClassNotFoundException just like with all the other well-known modules.

[metaruslan]

Should I create a separate issue for the problem I mentioned above? Just making sure I'm not missing anything, so that the new issue wouldn't be pointless.