Hadoop MapReduce 之wordcount

Hadoop MapReduce 之wordcount

package wordcount;

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
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;

/***
* MapReduce
* @author root
*
*/
public class WordCount {

//step1 : map class
public static class WordCountMapper extends Mapper<LongWritable, Text, Text, IntWritable>{

private Text mapOutputKey = new Text();
private final static IntWritable mapOutputValue = new IntWritable(1);

@Override
public void map(LongWritable key, Text value,Mapper<LongWritable, Text, Text, IntWritable>.Context context)
throws IOException, InterruptedException {

//line value
String lineValue = value.toString();
//split
//                String lineValue = value.toString();
StringTokenizer stringTokenizer = new StringTokenizer(lineValue);

//iterator
while(stringTokenizer.hasMoreTokens()) {
//get word value
String wordValue = stringTokenizer.nextToken();
// set key
mapOutputKey.set(wordValue);
//out put
context.write(mapOutputKey, mapOutputValue);
}
}

}

//step2 : reduce class
/***
*
*/
public static class WordCountReducer extends Reducer<Text, IntWritable, Text, IntWritable>{

private  IntWritable reduceOutputValue = new IntWritable();

@Override
public void reduce(Text key, Iterable<IntWritable> values,Reducer<Text, IntWritable, Text, IntWritable>.Context context)
throws IOException, InterruptedException {
//sum tmp
int sum=0;
//iterator
for(IntWritable value : values) {
// total
sum += value.get();
}
//set value
reduceOutputValue.set(sum);
//output
context.write(key, reduceOutputValue);
}

}

//step3 : driver,component job
public  int run(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
//1 get configuration
Configuration configuration = new Configuration();

//2 create job
Job job =  Job.getInstance(configuration, this.getClass().getSimpleName());

//run jar
job.setJarByClass(this.getClass());

//3 set job
//input -> map ->reduce -> output

//3.1 input
Path inPath = new Path(args[0]);
FileInputFormat.addInputPath(job, inPath);

//3.2 map
job.setMapperClass(WordCountMapper.class);
job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(IntWritable.class);

//3.3 reduce
job.setReducerClass(WordCountReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);

//3.4 output
Path outPath = new Path(args[1]);
FileOutputFormat.setOutputPath(job, outPath);

//4 submit job
boolean isSuccess = job.waitForCompletion(true);

return isSuccess? 0 : 1;

}

//step 5 run program
public static void main(String[] args) throws ClassNotFoundException, IOException, InterruptedException {

int status = new WordCount().run(args);
System.exit(status);
}
}