Create hadoop Reducer - Java Big Data

Java examples for Big Data:Hadoop

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Description

Create hadoop Reducer

Demo Code



import java.io.IOException;
import java.util.Iterator;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

/**/*from   ww  w .  j a  v a  2s .co  m*/
 * @author admln
 *
 */
public class CountWeixin {
  
  enum Counter {
    TIMESKIP,     
    IPSKIP,       
    URLSKIP,      
    SERSKIP,      
  }
  /**
   * 
   * Map
   *
   */
  public static class countWeixinMapper extends Mapper<Object,Text,Text,IntWritable> {
    public final static IntWritable ONE = new IntWritable(1);
    public Text word = new Text();
    
    @Override
    public void setup(Context context) {
      
    }
    
    @Override
    public void map(Object key,Text value,Context context) throws IOException, InterruptedException{
        
        //word.set(your value);
        //context.write(word, ONE);
        //context.getCounter(Counter.IPSKIP).increment(1);

    }
    
    @Override
    public void cleanup(Context context) {
      
    }
  }
  
  /**
   * 
   * Reduce
   */
  public static class countWeixinReducer extends Reducer<Text,IntWritable,Text,IntWritable> {
    
    int all = 0;
    int sum = 0;
    
    @Override
    public void setup(Context context) throws IOException, InterruptedException {
      
    }
    
    public void reduce(Text key,Iterable<IntWritable> values,Context context) throws IOException, InterruptedException {
      Iterator<IntWritable> ite = values.iterator();
      sum = 0;
      while(ite.hasNext()) {
        all++;
        sum++;
        ite.next();
      }
      context.write(key, new IntWritable(sum));
    }
    
    @Override
    public void cleanup(Context context) throws IOException, InterruptedException {
      context.write(new Text("test"), new IntWritable(all));
    }
  }
  
  @SuppressWarnings("deprecation")
  public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
    Path input = new Path("hdfs://192.168.32.131/in/yourApp/");
    Path output = new Path("hdfs://192.168.32.131/out/yourAppcountWeixin/");
    
    Configuration conf = new Configuration();
    
    Job job = new Job(conf,"countWeixin");
    
    job.setJarByClass(CountWeixin.class);
    
    job.setMapperClass(countWeixinMapper.class);
    job.setReducerClass(countWeixinReducer.class);
    
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(IntWritable.class);
    
    FileInputFormat.addInputPath(job, input);
    FileOutputFormat.setOutputPath(job, output);
    
    System.exit(job.waitForCompletion(true)?0:1);
  }

}

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