Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ // Modified by Shimin Chen to demonstrate functionality for Homework 2 // April-May 2015 import java.io.DataInput; import java.io.DataOutput; import java.io.IOException; import java.net.URI; import java.util.StringTokenizer; import java.util.regex.Pattern; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Hdfs; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.DoubleWritable; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.io.Writable; 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; import org.apache.hadoop.mapred.TextInputFormat; import org.apache.hadoop.mapred.TextOutputFormat; import org.apache.hadoop.util.GenericOptionsParser; public class Hw2Part1 { public static class InfoWritable implements Writable { int count; double time; InfoWritable() { } InfoWritable(int count, double time) { this.count = count; this.time = time; } public void SetValue(int count, double time) { this.count = count; this.time = time; } @Override public void readFields(DataInput in) throws IOException { // TODO Auto-generated method stub this.count = in.readInt(); this.time = in.readDouble(); } @Override public void write(DataOutput out) throws IOException { // TODO Auto-generated method stub out.writeInt(count); out.writeDouble(time); } public String toString() { return count + " " + time; } } // This is the Mapper class // reference: http://hadoop.apache.org/docs/r2.6.0/api/org/apache/hadoop/mapreduce/Mapper.html // public static class TokenizerMapper extends Mapper<Object, Text, Text, InfoWritable> { private Text source_destination = new Text(); final InfoWritable info = new InfoWritable(); public void map(Object key, Text value, Context context) throws IOException, InterruptedException { StringTokenizer itr = new StringTokenizer(value.toString()); // if the number of tokens is not 3,skip it if (itr.countTokens() != 3) { System.out.println("number of tokens is not 3"); return; } source_destination.set(itr.nextToken() + " " + itr.nextToken());//get the source_destination String timestr = itr.nextToken(); // if the 3rd token is not double,skip it if (!timestr.matches("^[.\\d]*$")) { System.out.println("the 3rd token is not double"); return; } Double time = Double.parseDouble(timestr);//get the time int one = 1; info.SetValue(one, time); context.write(source_destination, info); System.out.println(source_destination + "\t" + one + "\t" + time); } } public static class IntSumCombiner extends Reducer<Text, InfoWritable, Text, InfoWritable> { private InfoWritable result = new InfoWritable(); public void reduce(Text key, Iterable<InfoWritable> values, Context context) throws IOException, InterruptedException { int count = 0; double time = 0; for (InfoWritable val : values) { count += val.count; time += val.time; System.out.println(key + ": " + val.count + ", " + val.time); } result.SetValue(count, time); context.write(key, result); System.out.println(key + ": " + count + ", " + time); } } // This is the Reducer class // reference http://hadoop.apache.org/docs/r2.6.0/api/org/apache/hadoop/mapreduce/Reducer.html // // We want to control the output format to look at the following: // // count of word = count // public static class IntSumReducer extends Reducer<Text, InfoWritable, Text, InfoWritable> { private Text result_key = new Text(); private InfoWritable result_value = new InfoWritable(); public void reduce(Text key, Iterable<InfoWritable> values, Context context) throws IOException, InterruptedException { int count = 0; double time = 0; for (InfoWritable val : values) { count += val.count; time += val.time; } System.out.println(key + ":" + count + "," + time); time = time / (double) count;//get the average time time = (double) (Math.round(time * 1000) / 1000.0);//convert to the needed format System.out.println(time); result_key = key; // generate result value // result_value.set(Integer.toString(count)+" "+Double.toString(time)); result_value.SetValue(count, time); context.write(result_key, result_value); } } public static void main(String[] args) throws Exception { Configuration conf = new Configuration(); String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs(); if (otherArgs.length < 2) { System.err.println("Usage: <input file> <output directory>"); System.exit(2); } // FileSystem hdfs = FileSystem.get(conf); String target = "hdfs://localhost:9000/"; FileSystem fs = FileSystem.get(URI.create(target), conf);//is diffrent Path outputpath = new Path(otherArgs[otherArgs.length - 1]); if (fs.exists(outputpath)) { fs.delete(outputpath, true); } Job job = Job.getInstance(conf, "Hw2Part1"); job.setJarByClass(Hw2Part1.class); job.setMapperClass(TokenizerMapper.class); job.setCombinerClass(IntSumCombiner.class); job.setReducerClass(IntSumReducer.class); job.setMapOutputKeyClass(Text.class); job.setMapOutputValueClass(InfoWritable.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(InfoWritable.class); // add the input paths as given by command line for (int i = 0; i < otherArgs.length - 1; ++i) { FileInputFormat.addInputPath(job, new Path(otherArgs[i])); } // add the output path as given by the command line FileOutputFormat.setOutputPath(job, new Path(otherArgs[otherArgs.length - 1])); System.exit(job.waitForCompletion(true) ? 0 : 1); } }