Spring 4.0.0-M1 breaks springdoc due to java.lang.NoClassDefFoundError: kotlin/reflect/full/KClasses

[Algieba4]

Describe the bug

When upgrading from Spring 3.5.4 to Spring 4.0.0-M1 (yes, I know I'm very early in this migration effort), my program will build and pass tests though I get the following stacktrace when trying to run my application.

Error starting ApplicationContext. To display the condition evaluation report re-run your application with 'debug' enabled.
2025-08-01T17:22:40.146-05:00 ERROR 36992 --- [           main] [                                                 ] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springdoc.core.configuration.SpringDocKotlinConfiguration': Unexpected exception during bean creation
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:539) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:333) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:371) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:331) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:196) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.instantiateSingleton(DefaultListableBeanFactory.java:1207) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingleton(DefaultListableBeanFactory.java:1173) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:1109) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:978) ~[spring-context-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:618) ~[spring-context-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.boot.web.server.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:142) ~[spring-boot-web-server-4.0.0-M1.jar:4.0.0-M1]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737) ~[spring-boot-4.0.0-M1.jar:4.0.0-M1]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:435) ~[spring-boot-4.0.0-M1.jar:4.0.0-M1]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-4.0.0-M1.jar:4.0.0-M1]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1344) ~[spring-boot-4.0.0-M1.jar:4.0.0-M1]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1333) ~[spring-boot-4.0.0-M1.jar:4.0.0-M1]
	at com.example.MyExample.main(McsSps.java:10) ~[classes/:na]
Caused by: java.lang.NoClassDefFoundError: kotlin/reflect/full/KClasses
	at org.springframework.beans.BeanUtils$KotlinDelegate.findPrimaryConstructor(BeanUtils.java:878) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.BeanUtils.findPrimaryConstructor(BeanUtils.java:283) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:372) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineConstructorsFromBeanPostProcessors(AbstractAutowireCapableBeanFactory.java:1322) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1219) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:566) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:526) ~[spring-beans-7.0.0-M7.jar:7.0.0-M7]
	... 16 common frames omitted
Caused by: java.lang.ClassNotFoundException: kotlin.reflect.full.KClasses
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:580) ~[na:na]
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:490) ~[na:na]
	... 23 common frames omitted

When I disable springdoc.api-docs (springdoc.api-docs.enabled=false), I'm able to run my application in Spring 4.x. I didn't have to disable springdoc.swagger-ui

To Reproduce
Steps to reproduce the behavior:

• What version of spring-boot you are using:
  4.0.0-M1

• What modules and versions of springdoc-openapi are you using?

    <dependency>
      <groupId>org.springdoc</groupId>
      <artifactId>springdoc-openapi-starter-webmvc-ui</artifactId>
      <version>2.8.9</version>
    </dependency>
...
    <dependency>
      <groupId>org.springdoc</groupId>
      <artifactId>springdoc-openapi-ui</artifactId>
      <version>1.8.0</version>
    </dependency>

• Provide with a sample code (HelloController) or Test that reproduces the problem
  Issue appears when code is executing though below is my configuration and example (not my actual) controller

@Configuration
public class SwaggerConfig {
    @Bean
    public OpenAPI customOpenAPI() {
        return new OpenAPI()
            .info(new Info()
                .title("application")
                .version("1.0")
                .description("API documentation the accessing my applications endpoints"));
    }
}

@Slf4j
@CrossOrigin
@RestController
@RequestMapping(path = "/v1/controller")
@Tag(name = "My Controller", description = "Endpoints for executing my controller")
public class MyController {
    private final MyService myService;

    public MyController(MyService myService) {
        this.myService = myService;
    }

    @Operation(summary = "Gets information for a given date range",
            description = "Gets a count of all information for a given date range")
    @GetMapping(path = "/counts/{date}")
    public String getMyCounts(
            @Parameter(description = "Start date in yyyy-MM-dd format")
            @PathVariable("date") String date,
        return myService.getMyCounts(date);
    }
}

Expected behavior
I am expecting my code to compile and run successfully when using springdoc on Spring 4.x

Screenshots
N/A

Additional context
N/A