Dzmitry Lazerka created BEAM-4769:
-------------------------------------
Summary: Types$WildcardTypeImpl cannot be cast to
java.lang.reflect.TypeVariable
Key: BEAM-4769
URL: https://issues.apache.org/jira/browse/BEAM-4769
Project: Beam
Issue Type: Bug
Components: sdk-java-core
Affects Versions: 2.5.0
Reporter: Dzmitry Lazerka
Assignee: Kenneth Knowles
Hi,
I'm getting the following exception, probably when Beam cannot find a coder for
a wildcard generic type (although I don't think I use any, gotta find).
{{Exception in thread "main" java.lang.ClassCastException:
org.apache.beam.repackaged.beam_sdks_java_core.com.google.common.reflect.Types$WildcardTypeImpl
cannot be cast to java.lang.reflect.TypeVariable}}
{{at
org.apache.beam.sdk.coders.CoderRegistry.getCoderFromTypeDescriptor(CoderRegistry.java:625)}}
{{at
org.apache.beam.sdk.coders.CoderRegistry.getCoderFromParameterizedType(CoderRegistry.java:658)}}
{{at
org.apache.beam.sdk.coders.CoderRegistry.getCoderFromTypeDescriptor(CoderRegistry.java:620)}}
{{at
org.apache.beam.sdk.coders.CoderRegistry.getCoderFromParameterizedType(CoderRegistry.java:658)}}
{{at
org.apache.beam.sdk.coders.CoderRegistry.getCoderFromTypeDescriptor(CoderRegistry.java:620)}}
{{at org.apache.beam.sdk.coders.CoderRegistry.getCoder(CoderRegistry.java:254)}}
{{at
org.apache.beam.sdk.values.PCollection.inferCoderOrFail(PCollection.java:149)}}
{{at
org.apache.beam.sdk.values.PCollection.finishSpecifyingOutput(PCollection.java:89)}}
{{at
org.apache.beam.sdk.runners.TransformHierarchy.setOutput(TransformHierarchy.java:208)}}
{{at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:538)}}
{{at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:472)}}
{{at org.apache.beam.sdk.values.PCollection.apply(PCollection.java:286)}}
{{at org.apache.beam.sdk.transforms.ParDo$SingleOutput.expand(ParDo.java:649)}}
{{at org.apache.beam.sdk.transforms.ParDo$SingleOutput.expand(ParDo.java:584)}}
{{at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:537)}}
{{at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:491)}}
{{at org.apache.beam.sdk.values.PCollection.apply(PCollection.java:299)}}
{{at org.apache.beam.sdk.transforms.MapElements.expand(MapElements.java:123)}}
{{at org.apache.beam.sdk.transforms.MapElements.expand(MapElements.java:36)}}
{{at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:537)}}
{{at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:491)}}
{{at org.apache.beam.sdk.values.PCollection.apply(PCollection.java:299)}}
The error seems to be in the following lines of CoderRegistry.java @ 629:
{{} else if (type instanceof TypeVariable) {}}
{{ coder = getCoderFromFactories(typeDescriptor, Collections.emptyList());}}
{{} else if (type instanceof WildcardType) {}}
{{ // No coder for an unknown generic type.}}
{{ throw new CannotProvideCoderException(}}
{{ String.format("Cannot provide a coder for type variable %s"}}
{{ + " (declared by %s) because the actual type is unknown due to erasure.",}}
{{ type,}}
{{ ((TypeVariable<?>) type).getGenericDeclaration()),}}
{{ ReasonCode.TYPE_ERASURE);}}
It tries to cast a WildcardType to TypeVariable<?>, although that should've
been caught above on line 621.
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