Comments inline
On Thu, Oct 15, 2009 at 10:29 AM, yz5od2 <[email protected]>wrote:
> Hi,
> I am new to Hadoop so this might be an easy question for someone to help me
> with.
>
> I continually am getting this exception (my code follows below)
>
> java.io.IOException: Type mismatch in key from map: expected
> org.apache.hadoop.io.Text, recieved org.apache.hadoop.io.LongWritable
> at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:807)
> at
> org.apache.hadoop.mapred.MapTask$NewOutputCollector.write(MapTask.java:504)
> at
> org.apache.hadoop.mapreduce.TaskInputOutputContext.write(TaskInputOutputContext.java:80)
> at org.apache.hadoop.mapreduce.Mapper.map(Mapper.java:124)
> at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
> at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:583)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:305)
> at org.apache.hadoop.mapred.Child.main(Child.java:170)
>
>
> Running 0.20.1
>
> I have a text file with lines of data separated by carriage returns. This
> is properly stored in a directory within HDFS. I only have a Mapping task
> for processing this file, after the mapping is done it should go straight to
> output, No reduce or combiner functions.
>
> I am just trying to test to see if this will run. The mapper just takes the
> data sent to it and adds it back to the collector as 2 text values.
>
> --------------------
> My Mapper:
> --------------------
>
> public class MyTestMapper extends Mapper<LongWritable,Text,Text,Text> {
>
> public void map(Object key, Text value, Context context) throws
> IOException, InterruptedException {
>
Change the Object to Text and try again..
> String key = key.toString();
> String line = value.toString();
>
> String id = extractId(line);
> String reformattedLine = reformatLine(line);
>
> context.write(new Text(id), new Text(reformattedLine));
> }
> }
>
> --------------------
> My job submission code:
> -------------------------------------
>
> Job job = new Job(conf);
> job.setJarByClass(MyTestMapper.class);
> job.setMapperClass(MyTestMapper.class);
>
> FileInputFormat.addInputPath(job, new Path("/myDir/sample.txt"));
> FileOutputFormat.setOutputPath(job, new
> Path("/myDir/output/results-"+System.currentTimeMillis()+".txt"));
>
> job.setMapOutputKeyClass(Text.class);
> job.setMapOutputValueClass(Text.class);
>
> job.setOutputKeyClass(Text.class);
> job.setOutputValueClass(Text.class);
>
> job.submit();
