Question

import java.io.IOException;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
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 ADDMapper extends MapReduceBase implements Mapper<LongWritable,
                              Text,Text,LongWritable>
{   @Override
public void map(LongWritable key, Text value,OutputCollector<Text,    LongWritable> output, Reporter r)throws IOException 
    {
    String s=value.toString();
         char[] words=s.toCharArray();
                    int wno=0;
                    int ino=0;
        for(int i=0;i<words.length;i++)
          {    

           String temp="";  
               for(int j=ino;j<words.length;j++)
                   {                        

                        if(words[j]!=' ')
                        {   temp+=words[j];
                        }
                        else
                        {
                            wno=j;
                        if(temp!="")
                        {     

                            ino=ino + key; //////POINT OF ERROR

        output.collect(new Text(temp),new LongWritable(ino));
                        }

                    temp="";

                        ino=wno+1;
                        break;
                        }

                  }
        } 
}

}

我想得到每个字符串的索引值，按字符串排序。
上面的代码既没有给出索引值也没有改变字符串。让输入文件：你好你好吗嗨，我是对的。你的工作怎么样？嗨，你没事。

输出：我50岁是7,33 嗨0,30,44 怎么3,14 。

Answer 1

您好Shivendra我写了下面的mapper逻辑，它将帮助您找到具有排序输出的每个字符串的索引。此代码的输出按其索引排序String，然后您可以在此输出上运行reducer。

String str=value.toString();
String[] tokens = str.split(" "); //split into words
//create hashmap for unique word
Map<String,Integer> uniqueString = new HashMap<String,Integer>();
for(int i=0;i<tokens.length;i++){
    uniqueString.put(tokens[i],1);
}       
//for sorting create TreeMap from above hash map
Map<String,Integer> map = new TreeMap<String,Integer>(uniqueString); 
 for (Map.Entry entry : map.entrySet()) {
    int index=0;
//find the index of the word
    index = str.indexOf((String)entry.getKey());
    while (index >= 0) {
            output.collect(new Text((String)entry.getKey()),new LongWritable(index));
            index = str.indexOf((String)entry.getKey(), index + 1);
    }
}

此逻辑的输出：上午：20，分别是：7，分别是：50，喜：0，喜：15，喜：47，如何：3，如何：30， I：1，我：16，我：18，我：24， I：34， I：48，是：34， job.:42， ok.:58， right.:23，你：11，你：37，你：54，您的：37

它可能对你有帮助。

Answer 2

请运行以下代码，它运行正常并提供您的预期输出。

在命令行参数中提供输入和输出路径。（args [0]，args [1]）

import java.io.IOException;
import java.util.*;
import java.util.Map.Entry;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapred.*;


    public class IndexCount {

       public static class Map extends MapReduceBase implements Mapper<LongWritable, Text, Text, IntWritable> {
         public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException {

           String str=value.toString();
           String[] tokens = str.split(" "); //split into words
           //create hashmap for unique word
           HashMap<String,Integer> uniqueString = new HashMap<String,Integer>();
           for(int i=0;i<tokens.length;i++){
               uniqueString.put(tokens[i],1);
           }       
           //for sorting create TreeMap from above hash map
           TreeMap<String, Integer> map = new TreeMap<String,Integer>(uniqueString); 
            for (Entry<String, Integer> entry : map.entrySet()) {
               int index=0;
           //find the index of the word
               index = str.indexOf((String)entry.getKey());
               while (index >= 0) {
                       output.collect(new Text((String)entry.getKey()),new IntWritable(index));
                       index = str.indexOf((String)entry.getKey(), index + 1);
               }
           }
       }
    }
       public static class Reduce extends MapReduceBase implements Reducer<Text, IntWritable, Text, IntWritable> {
         public void reduce(Text key, Iterator<IntWritable> values, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException {

           while (values.hasNext()) {
               output.collect(key, new IntWritable(values.next().get()));
           }

         } 
    }
       public static void main(String[] args) throws Exception {
         JobConf conf = new JobConf(WordCount.class);
         conf.setJobName("indexfinder");

         conf.setOutputKeyClass(Text.class);
         conf.setOutputValueClass(IntWritable.class);
         conf.setMapperClass(Map.class);
         conf.setCombinerClass(Reduce.class);
         conf.setReducerClass(Reduce.class);    
         conf.setInputFormat(TextInputFormat.class);
         conf.setOutputFormat(TextOutputFormat.class);

         FileInputFormat.setInputPaths(conf, new Path(args[0]));
         FileOutputFormat.setOutputPath(conf, new Path(args[1]));

         JobClient.runJob(conf);
       }
    }

Answer 3

请运行以下代码，它会给出预期的输出。

   import java.io.IOException;
    import java.util.*;
    import java.util.Map.Entry;

     import org.apache.hadoop.fs.Path;
    import org.apache.hadoop.conf.*;
    import org.apache.hadoop.io.*;
    import org.apache.hadoop.mapreduce.*;
    import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
    import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
    import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
    import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;

     public class Index {

      public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {


         public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
             String str=value.toString();
               String[] tokens = str.split(" "); //split into words
               //create hashmap for unique word
               HashMap<String,Integer> uniqueString = new HashMap<String,Integer>();
               for(int i=0;i<tokens.length;i++){
                   uniqueString.put(tokens[i],1);
               }       
               //for sorting create TreeMap from above hash map
               TreeMap<String, Integer> map = new TreeMap<String,Integer>(uniqueString); 
               Configuration conf=context.getConfiguration();
               int strIndex = 0;
                for (Entry<String, Integer> entry : map.entrySet()) {
                   //int index=0;
                    strIndex=conf.getInt("index", 0);
               //find the index of the word
                   int index = str.indexOf((String)entry.getKey());
                   while (index >= 0) {
                            index+=strIndex;
                           context.write(new Text((String)entry.getKey()),new IntWritable(index));
                           index = str.indexOf((String)entry.getKey(), index + 1);
                   }
               }
                conf.setInt("index", strIndex+str.length());
           }
      } 

  public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> {

     public void reduce(Text key, Iterable<IntWritable> values, Context context) 
       throws IOException, InterruptedException {

         for (IntWritable val : values) {
             context.write(key, new IntWritable(val.get()));
        }
     }
  }

  public static void main(String[] args) throws Exception {
     Configuration conf = new Configuration();

        conf.setInt("index", 0);
         Job job = new Job(conf, "index");
     job.setOutputKeyClass(Text.class);
     job.setOutputValueClass(IntWritable.class);

     job.setMapperClass(Map.class);
     job.setReducerClass(Reduce.class);

     job.setInputFormatClass(TextInputFormat.class);
     job.setOutputFormatClass(TextOutputFormat.class);

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

     job.waitForCompletion(true);
  }

 }

Hadoop map-reduce映射器编程

3 个答案: