尝试运行MRUnit示例时API冲突

问题描述

我一直在玩MRUnit，并尝试按照单词计数和单元测试

I've been playing around with MRUnit and tried running it for a hadoop wordcount example following the tutorial for wordcount and unit testing

尽管不是粉丝，但我一直在使用Eclipse来运行代码，而setMapper函数却一直报错

Though not a fan, I've been using Eclipse to run the code and I keep getting an error for setMapper function

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);
  }

错误消息:

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)

查找此问题，我认为这可能是API冲突，但是我不确定在哪里寻找它.其他人以前有这个问题吗?

Looking up this issue, I think it might be an API conflict but I'm not sure where to look for it. Anybody else have this issue before?

EDIT 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.

EDIT I'm using a user defined library with the hadoop2 jar and the latest Junit(4.10) jar in it.

编辑2 这是WordCountMapper的代码

EDIT 2 Here 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);
        }
    }
}

最终编辑/工作

原来我需要设置

WordCountMapper mapper = new WordCountMapper();

到

Mapper mapper = new WordCountMapper();

因为泛型存在问题.还需要将模仿库导入我的用户定义库中.

since there was an issue with generics. Also needed to import the mockito library into my user defined library.

推荐答案

确保您导入了正确的类，与上面我的程序在Reducer和reduce_test两个类中都具有正确的参数不同，我遇到了相同的错误，但是由于导入了错误的类我遇到了上面报告的相同错误消息

Make sure you have imported correct class, i have faced same error unlike above my program was having correct parameters in both classes Reducer and reduce_test but due to importing wrong class i have faced same error message which is reported above

错误导入的类-

导入org.apache.hadoop.mrunit.ReduceDriver;

import org.apache.hadoop.mrunit.ReduceDriver;

正确的课程---

导入org.apache.hadoop.mrunit.mapreduce.ReduceDriver;

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

对于mapper_test，如果您确定自己在Mapper__class和Mapper_test中的参数相同，则采用相同的解决方案

same solution in case of mapper_test, if you are sure that your parameters are same in Mapper__class and Mapper_test

这篇关于尝试运行MRUnit示例时API冲突的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！