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https://issues.apache.org/jira/browse/AVRO-1240?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13570708#comment-13570708
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Doug Cutting commented on AVRO-1240:
------------------------------------
There are cases where folks nest generic within specific & reflect &
vice-versa. One example is Pair<K,V> which can contain reflect, specific or
generic instances. There's also a test case in TestReflect called
testReflectWithinGeneric. So we can't change that without breaking
compatibility.
> SpecificDataumReader.next() can return a GenericData.Record resulting in a
> ClassCastException
> ---------------------------------------------------------------------------------------------
>
> Key: AVRO-1240
> URL: https://issues.apache.org/jira/browse/AVRO-1240
> Project: Avro
> Issue Type: Bug
> Components: java
> Affects Versions: 1.7.3
> Reporter: Brock Noland
> Assignee: Brock Noland
> Fix For: 1.7.4
>
> Attachments: AVRO-1240.patch
>
>
> The following reasonable code:
> {noformat}
> DatumReader<Test> reader = new SpecificDatumReader<Test>(Test.class);
> DataFileReader<Test> dataFileReader = new DataFileReader<Test>(file,
> reader);
> Test datum = null;
> while(dataFileReader.hasNext()) {
> datum = dataFileReader.next(datum);
> System.out.println(datum);
> }
> {noformat}
> Can result in a runtime exception:
> {noformat}
> $ java -cp avro-1.7.3.jar:$(hadoop classpath) org.apache.hadoop.util.RunJar
> target/avro-example-1.0-jar-with-dependencies.jar Sample target/test-file
> Exception in thread "main" java.lang.ClassCastException:
> org.apache.avro.generic.GenericData$Record cannot be cast to Test
> at Sample.main(Sample.java:27)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at org.apache.hadoop.util.RunJar.main(RunJar.java:208)
> {noformat}
> when the jar containing the specific class (Test in my example) is loaded
> from a different classloader than the avro jar itself. This occurs when run
> via the hadoop jar command but could occur in web containers or other
> locations as well.
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