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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