Avro - Hadoop: The Definitive Guide - page 428

@Override
public int run ( String [] args ) throws Exception {
if ( args . length != 2 ) {
System . err . printf ( "Usage: %s [generic options] <input>
<output>\n" ,
getClass (). getSimpleName ());
ToolRunner . printGenericCommandUsage ( System . err );
return - 1 ;
}
Job job = new Job ( getConf (), "Max temperature" );
job . setJarByClass ( getClass ());
job . getConfiguration (). setBoolean (
Job . MAPREDUCE_JOB_USER_CLASSPATH_FIRST , true );
FileInputFormat . addInputPath ( job , new Path ( args [ 0 ]));
FileOutputFormat . setOutputPath ( job , new Path ( args [ 1 ]));
AvroJob . setMapOutputKeySchema ( job , Schema . create ( Schema . Type . INT ));
AvroJob . setMapOutputValueSchema ( job , SCHEMA );
AvroJob . setOutputKeySchema ( job , SCHEMA );
job . setInputFormatClass ( TextInputFormat . class );
job . setOutputFormatClass ( AvroKeyOutputFormat . class );
job . setMapperClass ( MaxTemperatureMapper . class );
job . setReducerClass ( MaxTemperatureReducer . class );
return job . waitForCompletion ( true ) ? 0 : 1 ;
}
public static void main ( String [] args ) throws Exception {
int exitCode = ToolRunner . run ( new AvroGenericMaxTemperature (),
args );
System . exit ( exitCode );
}
}
This program uses the Generic Avro mapping. This frees us from generating code to rep-
resent records, at the expense of type safety (field names are referred to by string value,
such as "temperature" ). [ 84 ] The schema for weather records is inlined in the code for
convenience (and read into the SCHEMA constant), although in practice it might be more
maintainable to read the schema from a local file in the driver code and pass it to the map-