Spring Boot: Cannot load configuration class

I am currently creating my first Spring Boot application. Unfortunately, I get an error right at the beginning that I can’t understand.

---

POM
Only some rudimentary dependencies are defined here. Java 8 and Spring Boot 2.0.1 are to be used.

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.carWasher</groupId>
    <artifactId>carWasher</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.1.RELEASE</version>
    </parent>

    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>

    </dependencies>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

---

App
Here the application is defined as a SpringBoot application. The autoconfig should actually make everything work automatically.

package carWasher;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class App {

    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }

}

---

Console output

15:44:12.390 [main] DEBUG org.springframework.boot.devtools.settings.DevToolsSettings - Included patterns for restart : []
15:44:12.392 [main] DEBUG org.springframework.boot.devtools.settings.DevToolsSettings - Excluded patterns for restart : [/spring-boot-starter-[w-]+/, /spring-boot/target/classes/, /spring-boot-starter/target/classes/, /spring-boot-devtools/target/classes/, /spring-boot-actuator/target/classes/, /spring-boot-autoconfigure/target/classes/]
15:44:12.392 [main] DEBUG org.springframework.boot.devtools.restart.ChangeableUrls - Matching URLs for reloading : [file:/home/jschafer/Documents/workspace/carWasher/target/classes/]

  .   ____          _            __ _ _
 /\ / ___'_ __ _ _(_)_ __  __ _    
( ( )___ | '_ | '_| | '_ / _` |    
 \/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |___, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.0.1.RELEASE)

2022-05-02 15:44:12.656  INFO 8325 --- [  restartedMain] carWasher.App                            : Starting App on jschafer-VirtualBox with PID 8325 (/home/jschafer/Documents/workspace/carWasher/target/classes started by jschafer in /home/jschafer/Documents/workspace/carWasher)
2022-05-02 15:44:12.657  INFO 8325 --- [  restartedMain] carWasher.App                            : No active profile set, falling back to default profiles: default
2022-05-02 15:44:12.680  INFO 8325 --- [  restartedMain] ConfigServletWebServerApplicationContext : Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@36219864: startup date [Mon May 02 15:44:12 CEST 2022]; root of context hierarchy
2022-05-02 15:44:13.276 ERROR 8325 --- [  restartedMain] o.s.boot.SpringApplication               : Application run failed

java.lang.IllegalStateException: Cannot load configuration class: carWasher.App
    at org.springframework.context.annotation.ConfigurationClassPostProcessor.enhanceConfigurationClasses(ConfigurationClassPostProcessor.java:414) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanFactory(ConfigurationClassPostProcessor.java:254) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:284) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:128) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:694) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:532) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:395) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:327) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1255) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1243) ~[spring-boot-2.0.1.RELEASE.jar:2.0.1.RELEASE]
    at carWasher.App.main(App.java:10) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) ~[spring-boot-devtools-2.0.1.RELEASE.jar:2.0.1.RELEASE]
Caused by: java.lang.ExceptionInInitializerError: null
    at org.springframework.context.annotation.ConfigurationClassEnhancer.newEnhancer(ConfigurationClassEnhancer.java:122) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.context.annotation.ConfigurationClassEnhancer.enhance(ConfigurationClassEnhancer.java:110) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.context.annotation.ConfigurationClassPostProcessor.enhanceConfigurationClasses(ConfigurationClassPostProcessor.java:403) ~[spring-context-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    ... 17 common frames omitted
Caused by: org.springframework.cglib.core.CodeGenerationException: java.lang.reflect.InaccessibleObjectException-->Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @2e8c1c9b
    at org.springframework.cglib.core.ReflectUtils.defineClass(ReflectUtils.java:464) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:336) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:93) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:91) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.internal.LoadingCache$2.call(LoadingCache.java:54) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) ~[na:na]
    at org.springframework.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:61) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.internal.LoadingCache.get(LoadingCache.java:34) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData.get(AbstractClassGenerator.java:116) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:291) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.KeyFactory$Generator.create(KeyFactory.java:221) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.KeyFactory.create(KeyFactory.java:174) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.KeyFactory.create(KeyFactory.java:153) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.proxy.Enhancer.<clinit>(Enhancer.java:73) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    ... 20 common frames omitted
Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @2e8c1c9b
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354) ~[na:na]
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297) ~[na:na]
    at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:199) ~[na:na]
    at java.base/java.lang.reflect.Method.setAccessible(Method.java:193) ~[na:na]
    at org.springframework.cglib.core.ReflectUtils$1.run(ReflectUtils.java:61) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:569) ~[na:na]
    at org.springframework.cglib.core.ReflectUtils.<clinit>(ReflectUtils.java:52) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.KeyFactory$Generator.generateClass(KeyFactory.java:243) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:329) ~[spring-core-5.0.5.RELEASE.jar:5.0.5.RELEASE]
    ... 32 common frames omitted

2022-05-02 15:44:13.277  INFO 8325 --- [  restartedMain] ConfigServletWebServerApplicationContext : Closing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@36219864: startup date [Mon May 02 15:44:12 CEST 2022]; root of context hierarchy

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Screenshot Eclipse (STS)
The screenshot shows the situation in the IDE (Eclipse STS). IDE

Answer

The solution was to use spring-boot-starter-parent in version >= 2.1.0