NoClassDefFoundError: kotlin/reflect/full/KClasses with 2.0.0.M3, Webflux and Kotlin

Hi,

I have the following demo application

package de.springbootbuch.webflux_kotlin

import org.springframework.boot.SpringApplication
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
import org.springframework.http.MediaType.TEXT_HTML
import org.springframework.stereotype.Component
import org.springframework.web.reactive.function.server.ServerRequest
import org.springframework.web.reactive.function.server.ServerResponse.ok
import org.springframework.web.reactive.function.server.router
import reactor.core.publisher.Mono

@SpringBootApplication
class Application {
	@Component
	class Handler {
		fun sayHello(req: ServerRequest) =
			ok().body(
				Mono.just("Hello, ${req.queryParam("name").orElse("World")}"),
				String::class.java
			)

		fun andGoodbye(req: ServerRequest) =
			ok().body(
				Mono.just("Goodbye"),
				String::class.java
			)
	}

	@Configuration
	class RoutesConfig(val handler: Handler) {
		@Bean
		fun routes() = router {
			("/greetings" and accept(TEXT_HTML)).nest {
				GET("/hello", handler::sayHello)
				GET("/goodbye", handler::andGoodbye)
			}
		}
	}
}

fun main(args: Array<String>) {
	SpringApplication.run(Application::class.java, *args)
}

Build with Gradle:

buildscript {
    repositories {
        mavenCentral()
        maven { url "https://repo.spring.io/libs-snapshot" }
    }
    ext {
        ktVersion = "1.1.3"
        springBootVersion = "2.0.0.M3"
    }
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$ktVersion"
        classpath "org.jetbrains.kotlin:kotlin-allopen:$ktVersion"
        classpath "org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}"
    }
}

apply plugin: "kotlin"
apply plugin: "kotlin-spring"
apply plugin: "org.springframework.boot"
apply plugin: "io.spring.dependency-management"

compileKotlin {
    kotlinOptions {
        jvmTarget = "1.8"
    }
}

jar {
    baseName = "webflux_kotlin"
    version = "0.0.1-SNAPSHOT"
}

repositories {
    mavenCentral()
    maven { url "https://repo.spring.io/libs-snapshot" }
}

dependencies {
    compile "org.jetbrains.kotlin:kotlin-stdlib:$ktVersion"
    compile "org.springframework.boot:spring-boot-starter-webflux"
}

(Full source is here https://github.com/springbootbuch/webflux_kotlin).

It compiles and builds fine with Spring Boot 2.0.0.M2 and 2.0.0.M3, but doesn’t run anymore with 2.0.0.M3. It fails to instantiate Jacksons ObjectMapper:

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.fasterxml.jackson.databind.ObjectMapper]: Factory method 'jacksonObjectMapper' threw exception; nested exception is java.lang.NoClassDefFoundError: kotlin/reflect/full/KClasses

and earlier to that I see a ClassCastException:

2017-08-09 10:17:43.057  WARN 14058 --- [           main] o.s.b.c.e.EventPublishingRunListener     : Error calling ApplicationEventListener

java.lang.ClassCastException: org.springframework.boot.context.event.ApplicationFailedEvent cannot be cast to org.springframework.boot.web.context.WebServerInitializedEvent
	at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:159) [spring-context-5.0.0.RC3.jar!/:5.0.0.RC3]
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) [spring-context-5.0.0.RC3.jar!/:5.0.0.RC3]
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127) [spring-context-5.0.0.RC3.jar!/:5.0.0.RC3]
	at org.springframework.boot.context.event.EventPublishingRunListener.finished(EventPublishingRunListener.java:114) [spring-boot-2.0.0.M3.jar!/:2.0.0.M3]
	at org.springframework.boot.SpringApplicationRunListeners.callFinishedListener(SpringApplicationRunListeners.java:79) [spring-boot-2.0.0.M3.jar!/:2.0.0.M3]
	at org.springframework.boot.SpringApplicationRunListeners.finished(SpringApplicationRunListeners.java:72) [spring-boot-2.0.0.M3.jar!/:2.0.0.M3]
	at org.springframework.boot.SpringApplication.handleRunFailure(SpringApplication.java:803) [spring-boot-2.0.0.M3.jar!/:2.0.0.M3]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:338) [spring-boot-2.0.0.M3.jar!/:2.0.0.M3]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1245) [spring-boot-2.0.0.M3.jar!/:2.0.0.M3]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1233) [spring-boot-2.0.0.M3.jar!/:2.0.0.M3]
	at de.springbootbuch.webflux_kotlin.ApplicationKt.main(Application.kt:44) [classes!/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_131]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_131]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_131]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_131]
	at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48) [webflux_kotlin.jar:na]
	at org.springframework.boot.loader.Launcher.launch(Launcher.java:87) [webflux_kotlin.jar:na]
	at org.springframework.boot.loader.Launcher.launch(Launcher.java:50) [webflux_kotlin.jar:na]
	at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51) [webflux_kotlin.jar:na]

The full stack trace is attached stacktrace.txt.

Thanks for looking at that issue.

[wilkinsona]

This looks to be due to a change in Spring Framework as it also fails, although slightly differently, with Boot 2.0 M2 and Spring Framework 5.0 RC3.

It works fine with Spring Boot 2.0 M3 if you add a dependency on kotlin-reflect:

diff --git a/build.gradle b/build.gradle
index d2846e2..3167332 100644
--- a/build.gradle
+++ b/build.gradle
@@ -5,7 +5,7 @@ buildscript {
     }
     ext {
         ktVersion = "1.1.3"
-        springBootVersion = "2.0.0.M2"
+        springBootVersion = "2.0.0.M3"
     }
     dependencies {
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$ktVersion"
@@ -37,5 +37,6 @@ repositories {

 dependencies {
     compile "org.jetbrains.kotlin:kotlin-stdlib:$ktVersion"
+    compile "org.jetbrains.kotlin:kotlin-reflect:$ktVersion"
     compile "org.springframework.boot:spring-boot-starter-webflux"
 }

@sdeleuze may well be able to explain why the Framework now requires kotlin-reflect.

[wilkinsona]

Thanks for the detailed description of the problem and the sample project. The ClassCastException is due to SPR-15838. I think it’s unrelated to the NoClassDefFoundError.