Spring NPE when a bean has generic inline-class as a public property

• Kotlin 1.7.0
• Spring Boot 2.7.1

I have a service with a public property, myMap, typed as an inline class, which has a generic parameter.

@Service
class ValueClassService {
    val myMap = MyValueClass<String>(emptyMap())
}

@JvmInline
value class MyValueClass<T>(
    val map: Map<T, String>
) : Map<T, String> by map

However, I get an NPE when Spring starts up.

Failed to load ApplicationContext
java.lang.IllegalStateException: Failed to load ApplicationContext
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:132)
    ...
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name '...ValueClassService' defined in file [.../build/classes/kotlin/test/.../ValueClassService.class]: Initialization of bean failed; nested exception is java.lang.NullPointerException
    at app//org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:628)
    ...
Caused by: java.lang.NullPointerException
    at java.desktop/com.sun.beans.TypeResolver.resolve(TypeResolver.java:203)

Workarounds:

1. make the val myMap private
2. make value class MyValueClass non-generic

Test reproducer

import org.junit.jupiter.api.Test
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.test.context.SpringBootTest
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT
import org.springframework.stereotype.Service

@SpringBootTest(
    classes = [Application::class],
    webEnvironment = RANDOM_PORT
)
internal class ApplicationTest {

    @Autowired
    lateinit var valueClassService: ValueClassService

    @Test
    fun `test value class`() {
        println(valueClassService.myMap)
    }
}

Application.kt

import org.springframework.boot.autoconfigure.AutoConfigurationExcludeFilter
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.context.TypeExcludeFilter
import org.springframework.boot.context.properties.ConfigurationPropertiesScan
import org.springframework.boot.context.properties.EnableConfigurationProperties
import org.springframework.boot.runApplication
import org.springframework.context.annotation.ComponentScan
import org.springframework.context.annotation.ComponentScan.Filter
import org.springframework.context.annotation.FilterType.CUSTOM
import org.springframework.context.annotation.FullyQualifiedAnnotationBeanNameGenerator

@SpringBootApplication
@ComponentScan(
    basePackages = ["my.package"],
    excludeFilters = [
        Filter(type = CUSTOM, classes = [TypeExcludeFilter::class]),
        Filter(type = CUSTOM, classes = [AutoConfigurationExcludeFilter::class])
    ],
    nameGenerator = FullyQualifiedAnnotationBeanNameGenerator::class
)
@EnableConfigurationProperties
@ConfigurationPropertiesScan(basePackages = ["my.package"])
class Application

Stacktrace

Failed to load ApplicationContext
java.lang.IllegalStateException: Failed to load ApplicationContext
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:132)
    at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:124)
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:118)
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:83)
    at org.springframework.boot.test.autoconfigure.SpringBootDependencyInjectionTestExecutionListener.prepareTestInstance(SpringBootDependencyInjectionTestExecutionListener.java:43)
    at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:248)
    at org.springframework.test.context.junit.jupiter.SpringExtension.postProcessTestInstance(SpringExtension.java:138)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeTestInstancePostProcessors$8(ClassBasedTestDescriptor.java:363)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.executeAndMaskThrowable(ClassBasedTestDescriptor.java:368)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeTestInstancePostProcessors$9(ClassBasedTestDescriptor.java:363)
    at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
    at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:177)
    at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1655)
    at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
    at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
    at java.base/java.util.stream.StreamSpliterators$WrappingSpliterator.forEachRemaining(StreamSpliterators.java:312)
    at java.base/java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:735)
    at java.base/java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:734)
    at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:658)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeTestInstancePostProcessors(ClassBasedTestDescriptor.java:362)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$instantiateAndPostProcessTestInstance$6(ClassBasedTestDescriptor.java:283)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.instantiateAndPostProcessTestInstance(ClassBasedTestDescriptor.java:282)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$4(ClassBasedTestDescriptor.java:272)
    at java.base/java.util.Optional.orElseGet(Optional.java:369)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$5(ClassBasedTestDescriptor.java:271)
    at org.junit.jupiter.engine.execution.TestInstancesProvider.getTestInstances(TestInstancesProvider.java:31)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$prepare$0(TestMethodTestDescriptor.java:102)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:101)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:66)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$prepare$2(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.prepare(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:90)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
    at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
    at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.processAllTestClasses(JUnitPlatformTestClassProcessor.java:99)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.access$000(JUnitPlatformTestClassProcessor.java:79)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.stop(JUnitPlatformTestClassProcessor.java:75)
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.stop(SuiteTestClassProcessor.java:61)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
    at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
    at com.sun.proxy.$Proxy5.stop(Unknown Source)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker$3.run(TestWorker.java:193)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:129)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:100)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:60)
    at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
    at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:133)
    at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:71)
    at worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
    at worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name '...ValueClassService' defined in file [.../build/classes/kotlin/test/.../ValueClassService.class]: Initialization of bean failed; nested exception is java.lang.NullPointerException
    at app//org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:628)
    at app//org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542)
    at app//org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335)
    at app//org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
    at app//org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333)
    at app//org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208)
    at app//org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:955)
    at app//org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918)
    at app//org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583)
    at app//org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:147)
    at app//org.springframework.boot.SpringApplication.refresh(SpringApplication.java:734)
    at app//org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:408)
    at app//org.springframework.boot.SpringApplication.run(SpringApplication.java:308)
    at app//org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:132)
    at app//org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:99)
    at app//org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:124)
    ... 88 more
Caused by: java.lang.NullPointerException
    at java.desktop/com.sun.beans.TypeResolver.resolve(TypeResolver.java:203)
    at java.desktop/com.sun.beans.TypeResolver.resolve(TypeResolver.java:218)
    at java.desktop/com.sun.beans.TypeResolver.resolve(TypeResolver.java:169)
    at java.desktop/com.sun.beans.TypeResolver.resolveInClass(TypeResolver.java:81)
    at java.desktop/com.sun.beans.introspect.MethodInfo.resolve(MethodInfo.java:63)
    at java.desktop/com.sun.beans.introspect.MethodInfo.<init>(MethodInfo.java:50)
    at java.desktop/com.sun.beans.introspect.PropertyInfo.add(PropertyInfo.java:245)
    at java.desktop/com.sun.beans.introspect.PropertyInfo.get(PropertyInfo.java:285)
    at java.desktop/com.sun.beans.introspect.ClassInfo.getProperties(ClassInfo.java:82)
    at java.desktop/java.beans.Introspector.getTargetPropertyInfo(Introspector.java:516)
    at java.desktop/java.beans.Introspector.getBeanInfo(Introspector.java:464)
    at java.desktop/java.beans.Introspector.getBeanInfo(Introspector.java:295)
    at java.desktop/java.beans.Introspector.getBeanInfo(Introspector.java:237)
    at org.springframework.beans.CachedIntrospectionResults.getBeanInfo(CachedIntrospectionResults.java:254)
    at org.springframework.beans.CachedIntrospectionResults.<init>(CachedIntrospectionResults.java:279)
    at org.springframework.beans.CachedIntrospectionResults.forClass(CachedIntrospectionResults.java:183)
    at org.springframework.beans.BeanWrapperImpl.getCachedIntrospectionResults(BeanWrapperImpl.java:174)
    at org.springframework.beans.BeanWrapperImpl.getPropertyDescriptors(BeanWrapperImpl.java:248)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.filterPropertyDescriptorsForDependencyCheck(AbstractAutowireCapableBeanFactory.java:1594)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.filterPropertyDescriptorsForDependencyCheck(AbstractAutowireCapableBeanFactory.java:1574)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1434)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:619)
    ... 103 more

Comment From: wilkinsona

This is a Framework issue that's similar to https://github.com/spring-projects/spring-framework/issues/28638. We'll transfer it to the Framework team so that they can triage it.

Comment From: sdeleuze

Duplicated of #28638 that I just made a bit more generic.