java - 尝试运行 MRUnit 示例时出现冲突的 API

Question

我一直在研究 MRUnit，并尝试按照 wordcount 的教程为 hadoop wordcount 示例运行它和 unit testing

虽然不是粉丝，但我一直在使用 Eclipse 运行代码，但我一直收到 setMapper 函数的错误

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);
  }

错误信息:

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)

查找这个问题，我认为它可能是一个 API 冲突，但我不确定在哪里寻找它。以前有其他人遇到过这个问题吗？

编辑 我正在使用一个用户定义的库，其中包含 hadoop2 jar 和最新的 Junit(4.10) jar。

编辑 2 这是 WordCountMapper 的代码

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);
        }
    }
}

最终编辑/有效

原来我需要设置

WordCountMapper mapper = new WordCountMapper();

到

Mapper mapper = new WordCountMapper();

因为泛型存在问题。还需要将 mockito 库导入我的用户定义库。

Answer 1

这是你的问题

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

您的 WordCountMapper 输入类型 (Object) 与 MapDriver 输入类型 (LongWritable) 不兼容。将您的 Mapper 定义更改为

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

您可能还想将 map 方法参数从 Object key 更改为 LongWritable key。