[jira] [Comment Edited] (SPARK-19656) Can't load custom type from avro file to RDD with newAPIHadoopFile

["Eric Maynard (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-19656?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15895998#comment-15895998 ] 

Eric Maynard edited comment on SPARK-19656 at 3/5/17 12:58 AM:
---------------------------------------------------------------

Normally after getting the `datum` you should call `asInstanceOf` to cast it properly.
  
In any event in Spark 2.0 the easier way to achieve what you want is probably something like this:

{code:java}
    import com.databricks.spark.avro._
    val df = spark.read.avro("file.avro")
    val extracted = df.map(row => (row(0).asInstanceOf[MyCustomClass]))
{code}


was (Author: emaynard):
Normally after getting the `datum` you should call `asInstanceOf` to cast it properly.
  
In any event in Spark 2.0 the easier way to achieve what you want is probably something like this:

{code:scala}
    import com.databricks.spark.avro._
    val df = spark.read.avro("file.avro")
    val extracted = df.map(row => (row(0).asInstanceOf[MyCustomClass]))
{code}

> 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-unsubscribe@spark.apache.org
For additional commands, e-mail: issues-help@spark.apache.org