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();
                }
        }
}

错误：

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

请回复！

Answer 1

该死的......我的抵抗力已经崩溃了。

显然，goutput.collect(l, emit);正在投掷NPE。这意味着goutput在调用null时为close()。

这意味着永远不会调用map，或者使用output的{{1}}参数调用它。

我不知道Hadoop，但我怀疑根问题是你的null方法没有覆盖基类中的map方法，因为签名不同。最终结果是您的map方法未被调用，并且...... NPE。

hadoop空指针异常

1 个答案: