Hadoop null exception de pointeur

Question

import java.awt.image.BufferedImage; 
import java.awt.image.DataBufferByte; 
import java.awt.image.Raster; 
import java.io.ByteArrayInputStream; 
import java.io.IOException; 
import javax.imageio.ImageIO; 
import javax.xml.soap.Text; 


import org.apache.hadoop.fs.Path; 
import org.apache.hadoop.io.*; 
import org.apache.hadoop.mapred.*; 

public class blur { 
public static class BlurMapper extends MapReduceBase implements Mapper<Text, BytesWritable, LongWritable, BytesWritable> 
{ 
    OutputCollector<LongWritable, BytesWritable> goutput; 

    int IMAGE_HEIGHT = 240; 
    int IMAGE_WIDTH = 320; 
    public BytesWritable Gmiu; 
    public BytesWritable Gsigma; 
    public BytesWritable w; 
    byte[] bytes = new byte[IMAGE_HEIGHT*IMAGE_WIDTH*3]; 
    public BytesWritable emit = new BytesWritable(bytes); 
    int count = 0; 
    int initVar = 125; 
    public LongWritable l = new LongWritable(1); 

    public void map(Text key, BytesWritable file,OutputCollector<LongWritable, BytesWritable> output, Reporter reporter) throws IOException { 
//Read Current Image from File. 
        goutput = output; 
        //System.out.println("akhil langer"); 
        BufferedImage img = ImageIO.read(new ByteArrayInputStream(file.getBytes())); 
       // BufferedImage dest = null; 

        //Apply Blur on Filter Operation - External JAR 
        // BoxBlurFilter BlurOp = new BoxBlurFilter(10,10,2); 
        Raster ras=img.getData(); 
        DataBufferByte db= (DataBufferByte)ras.getDataBuffer(); 
        byte[] data = db.getData(); 
        byte[] byte1 = new byte[IMAGE_HEIGHT*IMAGE_WIDTH]; 
        byte[] byte2 = new byte[IMAGE_HEIGHT*IMAGE_WIDTH]; 
        for(int i=0;i<IMAGE_HEIGHT*IMAGE_WIDTH;i++) 
        { 
        byte1[i]=20; 
        byte2[i]=125; 
        } 
        byte [] oldmiu; 
        oldmiu = new byte[IMAGE_HEIGHT*IMAGE_WIDTH] ; 
        byte [] oldsigma; 
        oldsigma = new byte[IMAGE_HEIGHT*IMAGE_WIDTH] ; 
        if(count==0){ 
          Gmiu = new BytesWritable(data); 
          Gsigma = new BytesWritable(byte1); 
          w = new BytesWritable(byte2); 
          count++; 

        oldmiu= Gmiu.getBytes(); 


        oldsigma= Gmiu.getBytes(); 
        } 

         else{ 
          for(int i=0;i<IMAGE_HEIGHT*IMAGE_WIDTH;i++) 
          { 
           byte pixel = data[i]; 
           Double tempmiu=new Double(0.0); 
           Double tempsig=new Double(0.0); 
           Double weight = new Double(0.0); 
           double temp1=0; double alpha = 0.05; 
           tempmiu = (1-alpha)*oldmiu[i] + alpha*pixel; 
           temp1=temp1+(pixel-oldmiu[i])*(pixel-oldmiu[i]); 
           tempsig=(1-alpha)*oldsigma[i]+ alpha*temp1; 

           byte1[i] = tempmiu.byteValue(); 
           byte2[i]= tempsig.byteValue(); 
           Gmiu.set(byte1,i,1); 
           Gsigma.set(byte2,i,1); 
           byte1 = w.getBytes(); 
           Double w1=new Double((1-alpha)*byte1[i]+alpha*100); 
           byte2[i] = w1.byteValue(); 
           w.set(byte2,i,1); 
          } 

         } 
         byte1 = Gsigma.getBytes();      
         emit.set(byte1,0,IMAGE_HEIGHT*IMAGE_WIDTH); 
         byte1 = Gsigma.getBytes(); 
         emit.set(byte1,IMAGE_HEIGHT*IMAGE_WIDTH,IMAGE_HEIGHT*IMAGE_WIDTH); 
         byte1 = w.getBytes(); 
         emit.set(byte1,2*IMAGE_HEIGHT*IMAGE_WIDTH,IMAGE_HEIGHT*IMAGE_WIDTH); 
     } 

     @Override 
     public void close(){ 
      try{ 
       goutput.collect(l, emit); 
      } 
      catch(Exception e){ 
       e.printStackTrace(); 
       System.exit(-1); 
      } 

     } 

} 

     public static void main(String[] args) { 

       if(args.length!=2) { 

         System.err.println("Usage: blurvideo input output"); 
         System.exit(-1); 

       } 
       JobClient client = new JobClient(); 
       JobConf conf = new JobConf(blur.class); 


       conf.setOutputValueClass(BytesWritable.class); 
       conf.setInputFormat(SequenceFileInputFormat.class); 
       //conf.setNumMapTasks(n) 

       SequenceFileInputFormat.addInputPath(conf, new Path(args[0])); 
       SequenceFileOutputFormat.setOutputPath(conf, new Path(args[1])); 
       conf.setMapperClass(BlurMapper.class); 
       conf.setNumReduceTasks(0); 
       //conf.setReducerClass(org.apache.hadoop.mapred.lib.IdentityReducer.class); 

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

Erreur:

java.lang.NullPointerException at blur$BlurMapper.close(blur.java:99) at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:57) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:342) at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:138)

S'il vous plaît répondre!

Answer 1

Merde ... ma résistance s'est effondrée.

Évidemment, goutput.collect(l, emit); lance un NPE. Et cela signifie que goutput est null lorsque close() est appelée.

Cela signifie que map n'a jamais été appelé ou qu'il a été appelé avec un argument output qui était null.

Je ne sais pas Hadoop, mais je soupçonne que le problème racine est votre méthode map ne remplace pas la méthode map dans la classe de base, car la signature est différente. Le résultat net est que votre méthode map n'est pas appelée, et .... NPE.