Java – Conflicting APIs when trying to run MRUnit samples

I’ve been working on MRUnit and trying to follow the > tutorial runs it for the Hadoop WordCount sample unit testing

I’m not a fan though, I’ve been running code with Eclipse, but I’m getting errors with the setMapper function all the time

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;

import org.apache.hadoop.mrunit.mapreduce.MapDriver;
import org.apache.hadoop.mrunit.mapreduce.MapReduceDriver;
import org.apache.hadoop.mrunit.mapreduce.ReduceDriver;

import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;

import org.junit.Before;
import org.junit.Test;

public class TestWordCount {
  MapReduceDriver<LongWritable, Text, Text, IntWritable, Text, IntWritable> mapReduceDriver;
  MapDriver<LongWritable, Text, Text, IntWritable> mapDriver;
  ReduceDriver<Text, IntWritable, Text, IntWritable> reduceDriver;

@Before
  public void setUp() throws IOException
  {
      WordCountMapper mapper = new WordCountMapper();
      mapDriver = new MapDriver<LongWritable, Text, Text, IntWritable>();
      mapDriver.setMapper(mapper);  <--Issue here

WordCountReducer reducer = new WordCountReducer();
      reduceDriver = new ReduceDriver<Text, IntWritable, Text, IntWritable>();
      reduceDriver.setReducer(reducer);

mapReduceDriver = new MapReduceDriver<LongWritable, Text, Text, IntWritable,     Text, IntWritable>();
      mapReduceDriver.setMapper(mapper); <--Issue here
      mapReduceDriver.setReducer(reducer);
  }

Error message:

java.lang.Error: Unresolved compilation problems: 
    The method setMapper(Mapper<LongWritable,Text,Text,IntWritable>) in the type MapDriver<LongWritable,Text,Text,IntWritable> is not applicable for the arguments ( WordCountMapper)
    The method setMapper(Mapper<LongWritable,Text,Text,IntWritable>) in the type MapReduceDriver<LongWritable,Text,Text,IntWritable,Text,IntWritable> is not applicable for the arguments (WordCountMapper)

Looking up this issue, I thought it might be an API conflict, but I’m not sure where to look for it. Has anyone else encountered this issue before?

Edit I’m using a user-defined library that contains the hadoop2 jar and the latest Junit(4.10) jar.

Edit 2 This is the code for WordCountMapper

import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class WordCountMapper extends Mapper<Object, Text, Text, IntWritable> 
{

private final static IntWritable one = new IntWritable(1);
    private Text word = new Text();

public void map(Object key, Text value, Context context)throws IOException, InterruptedException 
    {
        StringTokenizer itr = new StringTokenizer(value.toString());
        while (itr.hasMoreTokens()) 
        {
            word.set(itr.nextToken());
            context.write(word, one);
        }
    }
}

Final edited/valid

Turns out I need to set it up

WordCountMapper mapper = new WordCountMapper();

to

Mapper mapper = new WordCountMapper();

Because there is a problem with generics. I also need to import the mockito library into my user-defined library.

This is your problem

public class WordCountMapper extends Mapper<Object, Text, Text, IntWritable>
....
MapDriver<LongWritable, Text, Text, IntWritable> mapDriver;

Your WordCountMapper input type (Object) is not compatible with the MapDriver input type (LongWritable). Change your Mapper definition to

class WordCountMapper extends Mapper<LongWritable, Text, Text, IntWritable>

You may also want to change the map method parameter from Object key to LongWritable key.