Java Hadoop与Eclipse的集成

我正在阅读和实施教程。最后，我实现了三个类：映射器、减速器和驱动程序。我复制了网页上给出的所有三个类的确切代码。但以下两个错误并没有消失：-

*****************映射器类*************************************************************

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;

public class WordCountMapper extends MapReduceBase    //////Here WordCountMapper was underlined as error source by Eclipse
    implements Mapper<LongWritable, Text, Text, IntWritable> {

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

  public void map(WritableComparable key, Writable value,
      OutputCollector output, Reporter reporter) throws IOException {

    String line = value.toString();
    StringTokenizer itr = new StringTokenizer(line.toLowerCase());
    while(itr.hasMoreTokens()) {
      word.set(itr.nextToken());
      output.collect(word, one);
    }
  }
}

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;

public class WordCount {

  public static void main(String[] args) {
    JobClient client = new JobClient();
    JobConf conf = new JobConf(WordCount.class);

    // specify output types
    conf.setOutputKeyClass(Text.class);
    conf.setOutputValueClass(IntWritable.class);

    // specify input and output dirs
    FileInputPath.addInputPath(conf, new Path("input"));  //////////FileInputPath was underlined
    FileOutputPath.addOutputPath(conf, new Path("output")); ////////FileOutputPath as underlined

    // specify a mapper
    conf.setMapperClass(WordCountMapper.class);

    // specify a reducer
    conf.setReducerClass(WordCountReducer.class);
    conf.setCombinerClass(WordCountReducer.class);

    client.setConf(conf);
    try {
      JobClient.runJob(conf);
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

错误是：

The type WordCountMapper must implement the inherited abstract method 
 Mapper<LongWritable,Text,Text,IntWritable>.map(LongWritable, Text, 
 OutputCollector<Text,IntWritable>, Reporter)

1. FileInputPath cannot be resolved
2. FileOutputPath cannot be resolved

---

有人能告诉我问题出在哪里吗？提前感谢。

使用

org.apache.hadoop.mapred.FileInputFormat

，

org.apache.hadoop.mapred.FileOutputFormat

并按如下方式修改代码：

    // specify input and output dirs
    FileInputFormat.addInputPath(conf, new Path("input"));  
    FileOutputFormat.addOutputPath(conf, new Path("output"));

---

正如Sachinjose所说，当我将代码更改为：-

 FileInputFormat.addInputPath(conf, new Path("input"));  
    FileOutputFormat.setOutputPath(conf, new Path("output"));

第一个错误在示例中也得到了解决（我正在复制user2357112的答案）：-

您尚未提供任何类型参数。映射器是一个通用接口；它通过输入和输出键和值类型的类型参数进行参数化。用您需要的类型在以下代码中填写K1、V1、K2和V2：

public class WordMapper extends MapReduceBase implements Mapper<K1, V1, K2, V2> {
    public void map(K1 key,
                    V1 value,
                    OutputCollector<K2, V2> output,
                    Reporter reporter)
            throws IOException {
        whatever();
    }
}

公共类WordMapper扩展MapReduceBase实现Mapper{
公共空隙图（K1键，
V1值，
输出采集器输出，
（记者）
抛出IOException{
随便什么；
}
}