content: package com.manning.hip.ch7.shortestpath;
  
  
  import org.apache.commons.io.*;
  import org.apache.commons.lang.*;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.*;
  import org.apache.hadoop.io.Text;
  import org.apache.hadoop.mapreduce.*;
  import org.apache.hadoop.mapreduce.lib.input.*;
  import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
  
  import java.io.*;
  import java.util.Iterator;
  
  public final class Main {
  
  
    public static final String TARGET_NODE = "shortestpath.targetnode";
  
    public static void main(String... args) throws Exception {
  
      String startNode = args[0];
      String targetNode = args[1];
      String inputFile = args[2];
      String outputDir = args[3];
  
      iterate(startNode, targetNode, inputFile, outputDir);
    }
  
    public static void iterate(String startNode, String targetNode,
                               String input, String output)
        throws Exception {
  
      Configuration conf = new Configuration();
      Path outputPath = new Path(output);
      outputPath.getFileSystem(conf).delete(outputPath, true);
      outputPath.getFileSystem(conf).mkdirs(outputPath);
  
      Path inputPath = new Path(outputPath, "input.txt");
  
      createInputFile(new Path(input), inputPath, startNode);
  
      int iter = 1;
  
      while (true) {
  
        Path jobOutputPath =
            new Path(outputPath, String.valueOf(iter));
  
        System.out.println("======================================");
        System.out.println("=  Iteration:    " + iter);
        System.out.println("=  Input path:   " + inputPath);
        System.out.println("=  Output path:  " + jobOutputPath);
        System.out.println("======================================");
  
        if(findShortestPath(inputPath, jobOutputPath, startNode, targetNode)) {
          break;
        }
        inputPath = jobOutputPath;
        iter++;
      }
    }
  
    public static void createInputFile(Path file, Path targetFile,
                                       String startNode)
        throws IOException {
      Configuration conf = new Configuration();
      FileSystem fs = file.getFileSystem(conf);
  
      OutputStream os = fs.create(targetFile);
      LineIterator iter = org.apache.commons.io.IOUtils
          .lineIterator(fs.open(file), "UTF8");
      while (iter.hasNext()) {
        String line = iter.nextLine();
  
        String[] parts = StringUtils.split(line);
        int distance = Node.INFINITE;
        if (startNode.equals(parts[0])) {
          distance = 0;
        }
        IOUtils.write(parts[0] + '\t' + String.valueOf(distance) + "\t\t",
            os);
        IOUtils.write(StringUtils.join(parts, '\t', 1, parts.length), os);
        IOUtils.write("\n", os);
      }
  
      os.close();
    }
  
    public static boolean findShortestPath(Path inputPath,
                                 Path outputPath, String startNode,
                                 String targetNode)
        throws Exception {
      Configuration conf = new Configuration();
      conf.set(TARGET_NODE, targetNode);
  
      Job job = new Job(conf);
      job.setJarByClass(Main.class);
      job.setMapperClass(Map.class);
      job.setReducerClass(Reduce.class);
  
      job.setInputFormatClass(KeyValueTextInputFormat.class);
  
      job.setMapOutputKeyClass(Text.class);
      job.setMapOutputValueClass(Text.class);
  
      FileInputFormat.setInputPaths(job, inputPath);
      FileOutputFormat.setOutputPath(job, outputPath);
  
      if (!job.waitForCompletion(true)) {
        throw new Exception("Job failed");
      }
  
      Counter counter = job.getCounters()
          .findCounter(Reduce.PathCounter.TARGET_NODE_DISTANCE_COMPUTED);
  
      if(counter != null && counter.getValue() > 0) {
        CounterGroup group = job.getCounters().getGroup(Reduce.PathCounter.PATH.toString());
        Iterator<Counter> iter = group.iterator();
        iter.hasNext();
        String path = iter.next().getName();
        System.out.println("==========================================");
        System.out.println("= Shortest path found, details as follows.");
        System.out.println("= ");
        System.out.println("= Start node:  " + startNode);
        System.out.println("= End node:    " + targetNode);
        System.out.println("= Hops:        "  + counter.getValue());
        System.out.println("= Path:        "  + path);
        System.out.println("==========================================");
        return true;
      }
      return false;
    }
  
  
  
  }
  