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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AVRO-1240) SpecificDataumReader.next() can return a GenericData.Record resulting in a ClassCastException
Date Mon, 04 Feb 2013 22:44:12 GMT

    [ https://issues.apache.org/jira/browse/AVRO-1240?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13570708#comment-13570708
] 

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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