Ilya Ryzhov ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=5f65f49... ) *updated* an issue Hibernate ORM ( https://hibernate.atlassian.net/browse/HHH?atlOrigin=eyJpIjoiYTFkYzQ1MjI1... ) / Bug ( https://hibernate.atlassian.net/browse/HHH-17013?atlOrigin=eyJpIjoiYTFkYz... ) HHH-17013 ( https://hibernate.atlassian.net/browse/HHH-17013?atlOrigin=eyJpIjoiYTFkYz... ) Parameter nullability check throws error ( https://hibernate.atlassian.net/browse/HHH-17013?atlOrigin=eyJpIjoiYTFkYz... ) Change By: Ilya Ryzhov ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=5f65f49... ) Entity class: {noformat}@Entity @Table(name = "human_table") class HumanEntity( @Id @GeneratedValue(generator = "human_id_seq") @SequenceGenerator(name = "human_id_seq", sequenceName = "human_id_seq", allocationSize = 1) @Column(name = "id") val id: Int? = null, @Column(name = "name") var name: String? = null, @Column(name = "gender") var gender: Gender? = null ) enum class Gender { MALE, FEMALE }{noformat} Repository methods with HQL: {noformat}interface HumanEntityRepository : JpaRepository<HumanEntity, Int> { @Query("select he from HumanEntity he where :names is null or he.name in :names ") fun findByNames(names: List<String>?): List<HumanEntity> @Query("select he from HumanEntity he where :genders is null or he.gender in :genders ") fun findByGender(genders: List<Gender>?): List<HumanEntity> } {noformat} Calling {{humanEntityRepository.findByGender(listOf(Gender.MALE, Gender.FEMALE))}} produces {noformat}java.lang.ClassCastException: class java.util.Arrays$ArrayList cannot be cast to class java.lang.Enum (java.util.Arrays$ArrayList and java.lang.Enum are in module java.base of loader 'bootstrap') at org.hibernate.type.descriptor.converter.internal.OrdinalEnumValueConverter.toRelationalValue(OrdinalEnumValueConverter.java:23) at org.hibernate.query.sqm.internal.SqmUtil.createJdbcParameterBindings(SqmUtil.java:320) at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.buildCacheableSqmInterpretation(ConcreteSqmSelectQueryPlan.java:358) at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.withCacheableSqmInterpretation(ConcreteSqmSelectQueryPlan.java:268) at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.performList(ConcreteSqmSelectQueryPlan.java:244) at org.hibernate.query.sqm.internal.QuerySqmImpl.doList(QuerySqmImpl.java:518) at org.hibernate.query.spi.AbstractSelectionQuery.list(AbstractSelectionQuery.java:367) at org.hibernate.query.Query.getResultList(Query.java:119) at org.springframework.data.jpa.repository.query.JpaQueryExecution$CollectionExecution.doExecute(JpaQueryExecution.java:129) at org.springframework.data.jpa.repository.query.JpaQueryExecution.execute(JpaQueryExecution.java:92) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:148) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:136) at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:136) at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:120) at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:164) at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:143) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:72) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:391) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:135) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.data.repository.core.support.MethodInvocationValidator.invoke(MethodInvocationValidator.java:94) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:244) at jdk.proxy2/jdk.proxy2.$Proxy214.findByGender(Unknown Source){noformat} Calling {{humanEntityRepository.findByNames(listOf("Alice", "Bob"))}} produces {noformat}Caused by: org.hibernate.HibernateException: Unknown wrap conversion requested: java.util.Arrays$ArrayList to java.lang.String : `org.hibernate.type.descriptor.java.StringJavaType` (java.lang.String) at org.hibernate.type.descriptor.java.JavaTypeHelper.unknownWrap(JavaTypeHelper.java:24) at org.hibernate.type.descriptor.java.AbstractClassJavaType.unknownWrap(AbstractClassJavaType.java:116) at org.hibernate.type.descriptor.java.StringJavaType.wrap(StringJavaType.java:103) at org.hibernate.type.descriptor.java.StringJavaType.coerce(StringJavaType.java:121) at org.hibernate.type.descriptor.java.StringJavaType.coerce(StringJavaType.java:27) at org.hibernate.query.internal.QueryParameterBindingImpl.coerce(QueryParameterBindingImpl.java:145) at org.hibernate.query.internal.QueryParameterBindingImpl.setBindValue(QueryParameterBindingImpl.java:112) at org.hibernate.query.spi.AbstractCommonQueryContract.setParameter(AbstractCommonQueryContract.java:825) at org.hibernate.query.spi.AbstractSelectionQuery.setParameter(AbstractSelectionQuery.java:775) at org.hibernate.query.sqm.internal.QuerySqmImpl.setParameter(QuerySqmImpl.java:1237) at org.hibernate.query.sqm.internal.QuerySqmImpl.setParameter(QuerySqmImpl.java:129) at org.springframework.data.jpa.repository.query.QueryParameterSetter$BindableQuery.setParameter(QueryParameterSetter.java:326) at org.springframework.data.jpa.repository.query.QueryParameterSetter$NamedOrIndexedQueryParameterSetter.lambda$setParameter$4(QueryParameterSetter.java:117) at org.springframework.data.jpa.repository.query.QueryParameterSetter$ErrorHandling$1.execute(QueryParameterSetter.java:140) at org.springframework.data.jpa.repository.query.QueryParameterSetter$NamedOrIndexedQueryParameterSetter.setParameter(QueryParameterSetter.java:117) at org.springframework.data.jpa.repository.query.ParameterBinder.bind(ParameterBinder.java:83) at org.springframework.data.jpa.repository.query.ParameterBinder.bind(ParameterBinder.java:75) at org.springframework.data.jpa.repository.query.ParameterBinder.bindAndPrepare(ParameterBinder.java:97) at org.springframework.data.jpa.repository.query.AbstractStringBasedJpaQuery.doCreateQuery(AbstractStringBasedJpaQuery.java:106) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.createQuery(AbstractJpaQuery.java:234) at org.springframework.data.jpa.repository.query.JpaQueryExecution$CollectionExecution.doExecute(JpaQueryExecution.java:129) at org.springframework.data.jpa.repository.query.JpaQueryExecution.execute(JpaQueryExecution.java:92) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:148) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:136) at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:136) at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:120) at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:164) at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:143) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:72) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:391) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) ... 80 more {noformat} Swapping the order of nullability check to {{select he from HumanEntity he where he.name in :names or :names is null}}  and calling {{humanEntityRepository.findByNames(listOf("Alice", "Bob"))}}results in {noformat}java.lang.AssertionError at org.hibernate.query.sqm.internal.SqmUtil.createJdbcParameterBindings(SqmUtil.java:275) at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.buildCacheableSqmInterpretation(ConcreteSqmSelectQueryPlan.java:358) at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.withCacheableSqmInterpretation(ConcreteSqmSelectQueryPlan.java:268) at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.performList(ConcreteSqmSelectQueryPlan.java:244) at org.hibernate.query.sqm.internal.QuerySqmImpl.doList(QuerySqmImpl.java:518) at org.hibernate.query.spi.AbstractSelectionQuery.list(AbstractSelectionQuery.java:367) at org.hibernate.query.Query.getResultList(Query.java:119) at org.springframework.data.jpa.repository.query.JpaQueryExecution$CollectionExecution.doExecute(JpaQueryExecution.java:129) at org.springframework.data.jpa.repository.query.JpaQueryExecution.execute(JpaQueryExecution.java:92) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:148) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:136) at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:136) at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:120) at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:164) at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:143) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:72) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:391) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:135) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.data.repository.core.support.MethodInvocationValidator.invoke(MethodInvocationValidator.java:94) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:244) at jdk.proxy2/jdk.proxy2.$Proxy233.findByNames(Unknown Source){noformat} {{humanEntityRepository.findByNames(emptyList())}} results in {noformat}java.util.NoSuchElementException at kotlin.collections.EmptyIterator.next(Collections.kt:20) at kotlin.collections.EmptyIterator.next(Collections.kt:15) at org.hibernate.query.sqm.internal.SqmUtil.createJdbcParameterBindings(SqmUtil.java:267) at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.buildCacheableSqmInterpretation(ConcreteSqmSelectQueryPlan.java:358) at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.withCacheableSqmInterpretation(ConcreteSqmSelectQueryPlan.java:268) at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.performList(ConcreteSqmSelectQueryPlan.java:244) at org.hibernate.query.sqm.internal.QuerySqmImpl.doList(QuerySqmImpl.java:518) at org.hibernate.query.spi.AbstractSelectionQuery.list(AbstractSelectionQuery.java:367) at org.hibernate.query.Query.getResultList(Query.java:119) at org.springframework.data.jpa.repository.query.JpaQueryExecution$CollectionExecution.doExecute(JpaQueryExecution.java:129) at org.springframework.data.jpa.repository.query.JpaQueryExecution.execute(JpaQueryExecution.java:92) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.doExecute(AbstractJpaQuery.java:148) at org.springframework.data.jpa.repository.query.AbstractJpaQuery.execute(AbstractJpaQuery.java:136) at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:136) at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:120) at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:164) at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:143) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:72) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:391) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:135) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.data.repository.core.support.MethodInvocationValidator.invoke(MethodInvocationValidator.java:94) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:244) at jdk.proxy2/jdk.proxy2.$Proxy228.findByNames(Unknown Source){noformat} But querying the same HQL with a list of single element works fine. 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