Propagate Bean `ClassLoader` to `MongoTypeMapper`

[chadshowalter]

Description

When I read a document using a repository, if the document has an abstract field with a concrete implementation and the first read of the document happens in a ForkJoinPool thread, the read fails with the following stacktrace:

java.util.concurrent.ExecutionException: org.springframework.data.mapping.model.MappingInstantiationException: Failed to instantiate com.example.demo.AbstractBase using constructor public com.example.demo.AbstractBase() with arguments
	at java.base/java.util.concurrent.ForkJoinTask.get(ForkJoinTask.java:1006) ~[na:na]
	at com.example.demo.DocService.readDocs(DocService.java:42) ~[classes!/:na]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64) ~[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:564) ~[na:na]
	at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:389) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:333) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor.postProcessBeforeInitialization(InitDestroyAnnotationBeanPostProcessor.java:157) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:440) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1796) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:620) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:944) ~[spring-beans-5.3.13.jar!/:5.3.13]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918) ~[spring-context-5.3.13.jar!/:5.3.13]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583) ~[spring-context-5.3.13.jar!/:5.3.13]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:765) ~[spring-boot-2.5.7.jar!/:2.5.7]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:445) ~[spring-boot-2.5.7.jar!/:2.5.7]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:338) ~[spring-boot-2.5.7.jar!/:2.5.7]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1354) ~[spring-boot-2.5.7.jar!/:2.5.7]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1343) ~[spring-boot-2.5.7.jar!/:2.5.7]
	at com.example.demo.DemoApplication.main(DemoApplication.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:64) ~[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:564) ~[na:na]
	at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49) ~[demo-0.0.1-SNAPSHOT.jar:na]
	at org.springframework.boot.loader.Launcher.launch(Launcher.java:108) ~[demo-0.0.1-SNAPSHOT.jar:na]
	at org.springframework.boot.loader.Launcher.launch(Launcher.java:58) ~[demo-0.0.1-SNAPSHOT.jar:na]
	at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88) ~[demo-0.0.1-SNAPSHOT.jar:na]
Caused by: org.springframework.data.mapping.model.MappingInstantiationException: Failed to instantiate com.example.demo.AbstractBase using constructor public com.example.demo.AbstractBase() with arguments
	at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator$MappingInstantiationExceptionEntityInstantiator.createInstance(ClassGeneratingEntityInstantiator.java:321) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator.createInstance(ClassGeneratingEntityInstantiator.java:89) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:367) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readDocument(MappingMongoConverter.java:340) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter$ConversionContext.convert(MappingMongoConverter.java:1932) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter$MongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1640) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter$AssociationAwareMongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1689) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter$AssociationAwareMongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1652) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mapping.model.PersistentEntityParameterValueProvider.getParameterValue(PersistentEntityParameterValueProvider.java:74) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.mapping.model.SpELExpressionParameterValueProvider.getParameterValue(SpELExpressionParameterValueProvider.java:53) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator.extractInvocationArguments(ClassGeneratingEntityInstantiator.java:276) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator$EntityInstantiatorAdapter.createInstance(ClassGeneratingEntityInstantiator.java:248) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.mapping.model.ClassGeneratingEntityInstantiator.createInstance(ClassGeneratingEntityInstantiator.java:89) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:367) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.readDocument(MappingMongoConverter.java:340) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:276) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:272) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:101) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.MongoTemplate$ReadDocumentCallback.doWith(MongoTemplate.java:3178) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.MongoTemplate.executeFindMultiInternal(MongoTemplate.java:2813) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:2543) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.MongoTemplate.doFind(MongoTemplate.java:2525) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.core.MongoTemplate.find(MongoTemplate.java:847) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.repository.support.SimpleMongoRepository.findAll(SimpleMongoRepository.java:428) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.repository.support.SimpleMongoRepository.findAll(SimpleMongoRepository.java:150) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at org.springframework.data.mongodb.repository.support.SimpleMongoRepository.findAll(SimpleMongoRepository.java:57) ~[spring-data-mongodb-3.2.7.jar!/:3.2.7]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64) ~[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:564) ~[na:na]
	at org.springframework.data.repository.core.support.RepositoryMethodInvoker$RepositoryFragmentMethodInvoker.lambda$new$0(RepositoryMethodInvoker.java:289) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:137) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:121) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:529) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:285) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:599) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.13.jar!/:5.3.13]
	at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:163) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:138) ~[spring-data-commons-2.5.7.jar!/:2.5.7]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.13.jar!/:5.3.13]
	at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97) ~[spring-aop-5.3.13.jar!/:5.3.13]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.13.jar!/:5.3.13]
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215) ~[spring-aop-5.3.13.jar!/:5.3.13]
	at com.sun.proxy.$Proxy45.findAll(Unknown Source) ~[na:na]
	at com.example.demo.DocService.lambda$readDocs$1(DocService.java:37) ~[classes!/:na]
	at java.base/java.util.concurrent.ForkJoinTask$AdaptedRunnableAction.exec(ForkJoinTask.java:1409) ~[na:na]
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290) ~[na:na]
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1016) ~[na:na]
	at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1665) ~[na:na]
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1598) ~[na:na]
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183) ~[na:na]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.example.demo.AbstractBase]: Class is abstract
	... 51 common frames omitted

Steps to Reproduce

I have created a project on github that illustrates the issue.

1. Check out the repository (https://github.com/chadshowalter/forkjoin-mongodb) and cd to the repo root
2. Build the jar: gradlew bootJar
3. Ensure mongodb is running and available at localhost:27017 (or alternately, provide cl args when running for an available mongodb)
4. Run the built app: java -jar build/libs/demo-0.0.1-SNAPSHOT.jar
5. Observe the problem
6. Run the built app using a non ForkJoinPool executor: java -jar build/libs/demo-0.0.1-SNAPSHOT.jar --demo.pool.forkjoin=false
7. Read happens without exception in this case

Environment I'm Using

OSX 11.6
mongodb 4.2.10
Spring Boot 2.5.7
java:

openjdk 15.0.2 2021-01-19
OpenJDK Runtime Environment Corretto-15.0.2.7.1 (build 15.0.2+7)
OpenJDK 64-Bit Server VM Corretto-15.0.2.7.1 (build 15.0.2+7, mixed mode, sharing)

Observations

I believe the issue is due to the classloader available when using ForkJoinPool. I do not consistently see the problem when running in my IDE (IntelliJ 2021.2.2), but I do consistently see it when running the built app. I can work around the issue using a custom ForkJoinWorkerThreadFactory, e.g.

public class MyForkJoinWorkerThreadFactory implements ForkJoinPool.ForkJoinWorkerThreadFactory {

     @Override
    public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
        return new MyForkJoinWorkerThread(pool);
    }

    private static class MyForkJoinWorkerThread extends ForkJoinWorkerThread {

        private MyForkJoinWorkerThread(final ForkJoinPool pool) {
            super(pool);
            // set the classloader here
            setContextClassLoader(Thread.currentThread().getContextClassLoader());
        }
    }
}

[mp911de]

This issue is indeed related to the class loader that is being used. SimpleTypeInformationMapper tries to load the class that is used as a type hint.

Running the packaged jar uses Spring Boot code to create a class loader for the packaged jar files. Running the project from the IDE comes with the JDK's app-classloader that has already all jars on the class path.

Specifically, obtaining the default classloader from the Runnable returns jdk.internal.loader.ClassLoaders$AppClassLoader for ForkJoinPool. Executors.newFixedThreadPool retains the Spring Boot classloader org.springframework.boot.loader.LaunchedURLClassLoader.

When you look into ThreadFactory of the individual executor services, you'll see that ThreadPoolExecutor doesn't set any class loaders while DefaultForkJoinWorkerThreadFactory uses ClassLoader.getSystemClassLoader() to set the class loaders for newly created threads.

Likely the difference is motivated by the assumption of a single ForkJoinPool that gets typically configured through system properties.

You can supply a custom ForkJoinWorkerThreadFactory if you want to use a custom fork-join thread pool.

Alternatively, annotate your concrete classes with a type alias annotation @TypeAlias("com.example.demo.Concrete1") and that will pre-register the classes upon startup with the MappingContext.

Paging @wilkinsona for awareness.

[wilkinsona]

Thanks, @mp911de. This is due to a somewhat unfortunate change in Java 9 that we've seen a few times before. See spring-projects/spring-boot#19427, for example.

[chadshowalter]

Thanks. Too bad this inconsistency is there. It's a bit of a booby trap.

I had not picked up on the ability to work around this issue with the @TypeAlias annotation. Thanks for pointing that out.

I also observe that it requires some extra work in the build to set ForkJoinPool.commonPool()'s threadFactory, e.g.,

java -Djava.util.concurrent.ForkJoinPool.common.threadFactory=com.example.demo.MyForkJoinWorkerThreadFactory -jar build/libs/demo-0.0.1-SNAPSHOT.jar

does not work unless the custom factory class is at the root of the jar. But it looks like the @TypeAlias workaround works with either a custom or the common ForkJoinPool.

[mp911de]

I wonder whether we could default to the Spring ClassLoader in SimpleTypeInformationMapper. I'm going to create a ticket for it as falling back to the contextual class loader creates quite some inconvenience.

[mp911de]

See spring-projects/spring-data-commons#2508

[chadshowalter]

Thanks! 👍