Hadoop 案例2----数据去重问题

2012-3-1 a

2012-3-2 b

2012-3-3 c

2012-3-4 d

2012-3-5 a

2012-3-6 b

2012-3-7 c

2012-3-3 c

2012-3-1 b

2012-3-2 a

2012-3-3 b

2012-3-4 d

2012-3-5 a

2012-3-6 c

2012-3-7 d

2012-3-3 c

package cn.edu.bjut.del;

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class DelMapper extends Mapper<LongWritable, Text, Text, IntWritable> {

@Override
protected void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
String line = value.toString().trim();
if(!"".equals(line)) {
context.write(new Text(line), new IntWritable(1));
}
}
}

package cn.edu.bjut.del;

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

public class DelReducer extends Reducer<Text, IntWritable, Text, NullWritable> {

@Override
protected void reduce(Text key, Iterable<IntWritable> value, Context context)
throws IOException, InterruptedException {
context.write(key, NullWritable.get());
}

}

package cn.edu.bjut.del;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class MainJob {
public static void main(String[] args) throws Exception {

Configuration conf = new Configuration();
Job job = new Job(conf, "del");
job.setJarByClass(MainJob.class);

job.setMapperClass(DelMapper.class);
job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(IntWritable.class);

job.setReducerClass(DelReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(NullWritable.class);

FileInputFormat.addInputPath(job, new Path(args[0]));
Path path = new Path(args[1]);
FileSystem fs = FileSystem.get(conf);
if(fs.exists(path)) {
fs.delete(path, true);
}
FileOutputFormat.setOutputPath(job, path);

job.waitForCompletion(true);
}
}