@DBRef(lazy = true) with a Kotlin data class throwing Cannot subclass final class error

Question

I am using Kotlin with Spring boot and Spring Data Mongodb. I am creating a many to many relationship between two kotlin data classes annotated with @Document. To prevent an infinite loop from occurring, I add a lazy = true to my @DBRefs. This is where the problem happens, my understanding is that kotlin data classes are final and the way the spring data mapper works is somehow by extending them? I am making assumptions here.

To go around this I have decided to create an interface that my kotlin data class extends. This solves the issue but looks so damn ugly! I don't want to continue doing this throughout the code.

@Document(collection="users")
data class User(
        val id: String,
        @DBRef(lazy = true) var organization: Organization?,
        @CreatedDate val createdAt: Date,
        @LastModifiedDate var updatedAt: Date
)

@Document("organizations")
data class Organization (
        val id: String,
        @DBRef(lazy = true) val owners: ArrayList<User>,
        @CreatedDate val createdAt: Date,
        @LastModifiedDate var updatedAt: Date
)

Error:

java.lang.IllegalArgumentException: Cannot subclass final class com.hshar.eggegg.model.Organization
    at org.springframework.cglib.proxy.Enhancer.generateClass(Enhancer.java:657) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:358) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.proxy.Enhancer.generate(Enhancer.java:582) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:110) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:108) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.core.internal.LoadingCache$2.call(LoadingCache.java:54) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at java.base/java.util.concurrent.FutureTask.run(Unknown Source) ~[na:na]
    at org.springframework.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:61) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.core.internal.LoadingCache.get(LoadingCache.java:34) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData.get(AbstractClassGenerator.java:134) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:319) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.proxy.Enhancer.createHelper(Enhancer.java:569) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.cglib.proxy.Enhancer.createClass(Enhancer.java:416) ~[spring-core-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.data.mongodb.core.convert.DefaultDbRefResolver.getEnhancedTypeFor(DefaultDbRefResolver.java:202) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.convert.DefaultDbRefResolver.createLazyLoadingProxy(DefaultDbRefResolver.java:170) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.convert.DefaultDbRefResolver.resolveDbRef(DefaultDbRefResolver.java:100) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$AssociationAwareMongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1435) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter$AssociationAwareMongoDbPropertyValueProvider.getPropertyValue(MappingMongoConverter.java:1401) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mapping.model.PersistentEntityParameterValueProvider.getParameterValue(PersistentEntityParameterValueProvider.java:71) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mapping.model.SpELExpressionParameterValueProvider.getParameterValue(SpELExpressionParameterValueProvider.java:49) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.convert.KotlinClassGeneratingEntityInstantiator$DefaultingKotlinClassInstantiatorAdapter.extractInvocationArguments(KotlinClassGeneratingEntityInstantiator.java:230) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.convert.KotlinClassGeneratingEntityInstantiator$DefaultingKotlinClassInstantiatorAdapter.createInstance(KotlinClassGeneratingEntityInstantiator.java:204) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.convert.ClassGeneratingEntityInstantiator.createInstance(ClassGeneratingEntityInstantiator.java:84) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:272) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:245) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:194) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:190) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.read(MappingMongoConverter.java:78) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.MongoTemplate$ReadDocumentCallback.doWith(MongoTemplate.java:3017) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.MongoTemplate.executeFindOneInternal(MongoTemplate.java:2626) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.MongoTemplate.doFindOne(MongoTemplate.java:2353) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.core.MongoTemplate.findById(MongoTemplate.java:843) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.mongodb.repository.support.SimpleMongoRepository.findById(SimpleMongoRepository.java:118) ~[spring-data-mongodb-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Unknown Source) ~[na:na]
    at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:359) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:200) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:644) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:608) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.lambda$invoke$3(RepositoryFactorySupport.java:595) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:595) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:59) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:93) ~[spring-aop-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.data.repository.core.support.MethodInvocationValidator.invoke(MethodInvocationValidator.java:99) ~[spring-data-commons-2.1.5.RELEASE.jar:2.1.5.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at com.sun.proxy.$Proxy98.findById(Unknown Source) ~[na:na]
    at com.hshar.eggegg.security.CustomUserDetailsService.loadUserById(CustomUserDetailsService.kt:25) ~[classes/:na]
    at com.hshar.eggegg.security.JwtAuthenticationFilter.doFilterInternal(JwtAuthenticationFilter.kt:38) ~[classes/:na]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.filter.CorsFilter.doFilterInternal(CorsFilter.java:96) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:74) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:215) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:178) ~[spring-security-web-5.1.4.RELEASE.jar:5.1.4.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:357) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:270) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.filterAndRecordMetrics(WebMvcMetricsFilter.java:117) ~[spring-boot-actuator-2.1.3.RELEASE.jar:2.1.3.RELEASE]
    at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:106) ~[spring-boot-actuator-2.1.3.RELEASE.jar:2.1.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) ~[na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) ~[na:na]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.16.jar:9.0.16]
    at java.base/java.lang.Thread.run(Unknown Source) ~[na:na]

Occurring after executing this line:

        val user = userRepository.findOne(id) ?:
                throw UsernameNotFoundException("User not found with id $id")

I'd really like a better way of doing this. I do not want to make an interface for each data class just to solve this issue.

Answer 1

This can be solved with Kotlin's All-open plugin.

If you are using Gradle, the configuration would look like this:

Dependency

plugins {
  id "org.jetbrains.kotlin.plugin.allopen" version "1.3.41"
}

Configuration

allOpen {
  annotation("org.springframework.data.mongodb.core.mapping.Document")
}

As you can see, we are setting the Document annotation as a target for transformation. After that it just works.