[
https://issues.apache.org/jira/browse/AVRO-1240?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13569610#comment-13569610
]
Brock Noland commented on AVRO-1240:
------------------------------------
Doug,
Yes that the same approach I was considering and fixes the issue locally
(below). I do have one additional item to discuss. The Specific* readers are
generics and as such, the user expects that the next() method will never return
anything but the Specific class in question. Furthermore, if using the
Specific* it's likely a ClassCastException is going to be returned by returning
anything but the Specific class in question.
As such, inline with the fail fast and loudly principle, I wonder if instead of
punting up to the Generic*, a runtime exception with a good error message
should be thrown when the class for a schema cannot be found. I am not overly
familiar with the Avro source, so it's possible this would break something
badly. If the change is safe, then at least in this case, it would have made
for a much better user experience.
{noformat}
$ java -cp avro-1.7.4-SNAPSHOT.jar:$(hadoop classpath)
org.apache.hadoop.util.RunJar target/avro-example-1.0-jar-with-dependencies.jar
Sample target/test-file
{"left": "l", "right": "r"}
{noformat}
> 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.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
