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Using Stream as result of a query method failed due to expecting a singular result

See original GitHub issue

Despite what https://www.baeldung.com/spring-data-java-8 says, when I created a Stream<Foo> on a org.springframework.cloud.gcp.data.datastore.repository.DatastoreRepository implementation, I received this:

org.springframework.cloud.gcp.data.datastore.core.mapping.DatastoreDataException: The query method returns a singular object but the query returned more than one result.
  at org.springframework.cloud.gcp.data.datastore.repository.query.GqlDatastoreQuery.convertSingularResult (GqlDatastoreQuery.java:227)
  at org.springframework.cloud.gcp.data.datastore.repository.query.GqlDatastoreQuery.execute (GqlDatastoreQuery.java:156)
  at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke (RepositoryMethodInvoker.java:137)
  at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke (RepositoryMethodInvoker.java:121)
  at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke (QueryExecutorMethodInterceptor.java:152)
  at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke (QueryExecutorMethodInterceptor.java:131)
  at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed (ReflectiveMethodInvocation.java:186)
  at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke (ExposeInvocationInterceptor.java:97)
  at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed (ReflectiveMethodInvocation.java:186)
  at org.springframework.aop.framework.JdkDynamicAopProxy.invoke (JdkDynamicAopProxy.java:215)
  at com.sun.proxy.$Proxy104.getValidCarrierDirections (Unknown Source)

some investigation led me to org.springframework.data.repository.query.QueryMethod.isCollectionQuery()
then to org.springframework.data.repository.query.QueryMethod.calculateIsCollectionQuery()
then to org.springframework.data.util.TypeDiscoverer.isCollectionLike()

https://github.com/spring-projects/spring-data-commons/blob/main/src/main/java/org/springframework/data/util/TypeDiscoverer.java#L351-L359

Shouldn’t that list include java.util.stream.Stream?

Issue Analytics

State:
Created 2 years ago
Comments:8 (4 by maintainers)

Top GitHub Comments

1reaction

mp911decommented, Apr 29, 2021

Iterable is the lowest common denominator across the collection framework. We’re actually considering to retrofit CrudRepository with Spring Data 3.0 to return List to make it easier to consume findAll and other methods returning collections.

0reactions

nbalicommented, Apr 29, 2021

Well, I was lucky then, to have worked mostly with projects where Iterable meant a streaming result. I mean without that extra functionality why would anybody return an Iterable, when you cuold just return a Collection/List instead?

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