[jira] [Commented] (AVRO-1240) SpecificDataumReader.next() can return a GenericData.Record resulting in a ClassCastException

["Brock Noland (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AVRO-1240?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13568851#comment-13568851 ] 

Brock Noland commented on AVRO-1240:
------------------------------------

I have found three work arounds for this issue.

	
Change
{noformat}
    Test datum = null;
{noformat}
to
{noformat}
    Test datum = new Test();
{noformat}

Change
{noformat}
    DatumReader<Test> reader = new SpecificDatumReader<Test>(Test.class); 
{noformat}
to:
{noformat}
    DatumReader<Test> reader = new SpecificDatumReader<Test>(Test.SCHEMA$, Test.SCHEMA$, new SpecificData(Test.class.getClassLoader())); 
{noformat}
    
Put the jar containing the specific class in the classpath of the main JVM
That is change:

{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 
{noformat}
to
{noformat}
   $ java -cp avro-1.7.3.jar:$(hadoop classpath):target/avro-example-1.0-jar-with-dependencies.jar org.apache.hadoop.util.RunJar target/avro-example-1.0-jar-with-dependencies.jar Sample target/test-file 
{noformat}

or do the equivalent with the HADOOP_CLASSPATH variable.
                
> 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
>
> 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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