[
https://issues.apache.org/jira/browse/SPARK-19656?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15896268#comment-15896268
]
Sean Owen commented on SPARK-19656:
-----------------------------------
Yes, I just tried to compile your code example above, and it doesn't work, but,
for more basic reasons. That much is "Not A Problem" because you've got more
basic usage errors. That is, this is not an example of code that should work
but doesn't due to Avro issues. To the additional narrower question of whether
Datasets and casting works, it does, and I verified that it compiles.
> Can't load custom type from avro file to RDD with newAPIHadoopFile
> ------------------------------------------------------------------
>
> Key: SPARK-19656
> URL: https://issues.apache.org/jira/browse/SPARK-19656
> Project: Spark
> Issue Type: Question
> Components: Java API
> Affects Versions: 2.0.2
> Reporter: Nira Amit
>
> If I understand correctly, in scala it's possible to load custom objects from
> avro files to RDDs this way:
> {code}
> ctx.hadoopFile("/path/to/the/avro/file.avro",
> classOf[AvroInputFormat[MyClassInAvroFile]],
> classOf[AvroWrapper[MyClassInAvroFile]],
> classOf[NullWritable])
> {code}
> I'm not a scala developer, so I tried to "translate" this to java as best I
> could. I created classes that extend AvroKey and FileInputFormat:
> {code}
> public static class MyCustomAvroKey extends AvroKey<MyCustomClass>{};
> public static class MyCustomAvroReader extends
> AvroRecordReaderBase<MyCustomAvroKey, NullWritable, MyCustomClass> {
> // with my custom schema and all the required methods...
> }
> public static class MyCustomInputFormat extends
> FileInputFormat<MyCustomAvroKey, NullWritable>{
> @Override
> public RecordReader<MyCustomAvroKey, NullWritable>
> createRecordReader(InputSplit inputSplit, TaskAttemptContext
> taskAttemptContext) throws IOException, InterruptedException {
> return new MyCustomAvroReader();
> }
> }
> ...
> JavaPairRDD<MyCustomAvroKey, NullWritable> records =
> sc.newAPIHadoopFile("file:/path/to/datafile.avro",
> MyCustomInputFormat.class, MyCustomAvroKey.class,
> NullWritable.class,
> sc.hadoopConfiguration());
> MyCustomClass first = records.first()._1.datum();
> System.out.println("Got a result, some custom field: " +
> first.getSomeCustomField());
> {code}
> This compiles fine, but using a debugger I can see that `first._1.datum()`
> actually returns a `GenericData$Record` in runtime, not a `MyCustomClass`
> instance.
> And indeed, when the following line executes:
> {code}
> MyCustomClass first = records.first()._1.datum();
> {code}
> I get an exception:
> {code}
> java.lang.ClassCastException: org.apache.avro.generic.GenericData$Record
> cannot be cast to my.package.containing.MyCustomClass
> {code}
> Am I doing it wrong? Or is this not possible in Java?
--
This message was sent by Atlassian JIRA
(v6.3.15#6346)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org
For additional commands, e-mail: issues-h...@spark.apache.org
