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From Jason Venner <jason.had...@gmail.com>
Subject Re: help for beginner
Date Mon, 08 Feb 2010 14:50:32 GMT
This class of problem has a pretty standard answer

http://www.prohadoopbook.com/forum/topics/type-mismatch-error

On Wed, Feb 3, 2010 at 9:16 PM, Ma, Zhiqiang <zqmaster@gmail.com> wrote:

> Hi All,
>
> I am a beginner of Hadoop. I modified the Inverted Index Code in Yahoo's
> Tutorial  (
> http://developer.yahoo.com/hadoop/tutorial/module4.html#solution), but I
> always get errors of "java.io.IOException: Type mismatch in key from map:
> expected org.apache.hadoop.io.Text, recieved
> org.apache.hadoop.io.LongWritable". Could some people tell me what is wrong
> in my code? Thanks a million!
>
> Zhiqiang
>
> ----------------------------code
> starts--------------------------------------
> import java.io.IOException;
> import java.util.Iterator;
> import java.util.StringTokenizer;
>
> import org.apache.hadoop.conf.Configuration;
> import org.apache.hadoop.fs.Path;
> import org.apache.hadoop.io.LongWritable;
> import org.apache.hadoop.io.Text;
> import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
> import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
> import org.apache.hadoop.mapreduce.lib.input.FileSplit;
> import org.apache.hadoop.mapred.OutputCollector;
> import org.apache.hadoop.mapred.Reporter;
> import org.apache.hadoop.mapreduce.Job;
> import org.apache.hadoop.mapreduce.Mapper;
> import org.apache.hadoop.mapreduce.Reducer;
>
> public class YahooIndex {
>
>  public static class MyMapper extends Mapper<LongWritable, Text, Text,
> Text> {
>
>    private final static Text word = new Text();
>    private final static Text location = new Text();
>
>    public void map(LongWritable key, Text val,
>        OutputCollector<Text, Text> output, Reporter reporter)
>        throws IOException {
>
>      FileSplit fileSplit = (FileSplit)reporter.getInputSplit();
>      String fileName = fileSplit.getPath().getName();
>      location.set(fileName);
>
>      String line = val.toString();
>      StringTokenizer itr = new StringTokenizer(line.toLowerCase());
>      while (itr.hasMoreTokens()) {
>        word.set(itr.nextToken());
>        output.collect(word, location);
>      }
>    }
>  }
>
>
>
>  public static class MyReducer extends Reducer<Text, Text, Text, Text> {
>
>    public void reduce(Text key, Iterator<Text> values,
>        OutputCollector<Text, Text> output, Reporter reporter)
>        throws IOException {
>
>      boolean first = true;
>      StringBuilder toReturn = new StringBuilder();
>      while (values.hasNext()){
>        if (!first)
>          toReturn.append(", ");
>        first=false;
>        toReturn.append(values.next().toString());
>      }
>
>      output.collect(key, new Text(toReturn.toString()));
>    }
>  }
>
>
>  public static void main(String[] args) throws IOException,
> InterruptedException, ClassNotFoundException {
>          Configuration conf = new Configuration();
>        Job job = new Job(conf, "Example Hadoop 0.20.1 WordCount");
>        job.setJarByClass(YahooIndex.class);
>        job.setMapperClass(MyMapper.class);
>        job.setReducerClass(MyReducer.class);
>        job.setOutputKeyClass(Text.class);
>        job.setOutputValueClass(Text.class);
>        FileInputFormat.addInputPath(job, new Path("input"));
>        FileOutputFormat.setOutputPath(job, new Path("output"));
>        System.exit(job.waitForCompletion(true) ? 0 : 1);
>  }
> }
> -----------------------------------code
> ends-----------------------------------------------------------------------------------
>



-- 
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