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package com.fwmagic.mapreduce;
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;
import java.io.IOException;
/**
* MapReduce单词统计
*/
public class WordCountDemo {
/**
* 自定义Mapper继承:org.apache.hadoop.mapreduce.Mapper,实现map方法
*/
public static class WordCountMapper extends Mapper {
@Override
protected void map(LongWritable key, Text value,
Mapper.Context context)
throws IOException, InterruptedException {
String[] words = value.toString().split(" ");
for (String word : words) {
context.write(new Text(word), new IntWritable(1));
}
}
}
/**
* 自定义Reducer继承:org.apache.hadoop.mapreduce.Reducer,实现reduce方法
*/
public static class WordCountReducer extends Reducer {
@Override
protected void reduce(Text key, Iterable values,
Reducer.Context context)
throws IOException, InterruptedException {
int count = 0;
for (IntWritable writable : values) {
count += writable.get();
}
context.write(key, new IntWritable(count));
}
}
/**
* job启动类,设置参数并集群中提交job
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
Job job = Job.getInstance(conf);
job.setJarByClass(WordCountDemo.class);
job.setMapperClass(WordCountMapper.class);
job.setReducerClass(WordCountReducer.class);
job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(IntWritable.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
FileInputFormat.setInputPaths(job, new Path("/wordcount/input"));
FileOutputFormat.setOutputPath(job, new Path("/wordcount/output"));
boolean b = job.waitForCompletion(true);
System.exit(b ? 0 : 1);
}
}
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hadoop jar fwmagic-wordcount.jar