package com.averscore;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
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;
import org.apache.hadoop.util.GenericOptionsParser;
public class Entry {
@SuppressWarnings("deprecation")
public static void main(String arg[]) throws Exception {
Configuration conf = new Configuration();
String[] otherarg = new GenericOptionsParser(conf, arg).getRemainingArgs();
if (otherarg.length != 2) {
System.out.println("error!");
System.exit(2);
}
Job job = new Job(conf, "averscore");
job.setJarByClass(Entry.class);
job.setMapperClass(ScoreMapper.class);
job.setReducerClass(ScoreReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
FileInputFormat.addInputPath(job, new Path(arg[0]));
FileOutputFormat.setOutputPath(job, new Path(arg[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
package com.averscore;
import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
public class ScoreMapper extends Mapper<Object, Text, Text, IntWritable> {
private final static IntWritable num = new IntWritable();
private Text word = new Text();
public void map(Object key, Text value, Context context)
throws IOException, InterruptedException {
String []line=value.toString().split(" ");
word.set(line[0]);
num.set(Integer.parseInt(line[1]));
context.write(word, num);
}
}
package com.averscore;
import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
public class ScoreReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
private static IntWritable averscore = new IntWritable();
public void reduce(Text key, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
int cnt = 0;
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
cnt++;
}
int score=sum/cnt;
averscore.set(score);
context.write(key, averscore);
}
}
设计思路
Map输入key值是偏移量，value是字符串。首先按行划分（用参数“\n”），对每一行进行处理，按照空格划分。将姓名和成绩分开，输出的key值是姓名，value值是转换为整数的成绩（Integer.parseInt(String)）。