1 import java.io.*;
2 import java.util.*;
3
4 import org.apache.hadoop.fs.Path;
5 import org.apache.hadoop.io.*;
6 import org.apache.hadoop.mapreduce.*;
7 import org.apache.hadoop.mapreduce.lib.output.*;
8 import org.apache.hadoop.mapreduce.lib.input.*;
9 import org.apache.hadoop.conf.*;
10 import org.apache.hadoop.util.*;
11 public class Score_Process extends Configured implements Tool {
12 /**
13 * 程序说明：主要用来实现计算学生的平均成绩。
14 * 数据输入：文件形式输入，每一行包含学生姓名 学生成绩。一个学生有多门成绩则有多行。例如：张三 98
15 * 数据输出：张三 84 学生姓名 学生平均成绩
16 * 实现思路：在map阶段<张三，（98,68,……）>
17 * **/
18
19 public static class Map extends Mapper<LongWritable,Text,Text,IntWritable>{
20 public void map(LongWritable key,Text value,Context context)throws IOException,InterruptedException{
21 String line=value.toString();
22 System.out.println(line);//测试
23 StringTokenizer tokenizer=new StringTokenizer(line);
24 while(tokenizer.hasMoreTokens()){
25 String name=tokenizer.nextToken();
26 String strscore=tokenizer.nextToken();
27 int intscore=Integer.parseInt(strscore);
28 context.write(new Text(name), new IntWritable(intscore));
29 }
30
31 }
32
33 }
34
35 public static class Reduce extends Reducer<Text,IntWritable,Text,IntWritable>{
36 public void reduce(Text key,Iterable<IntWritable>values,Context context) throws IOException, InterruptedException{
37 int sun=0,count=0;
38 for(IntWritable val:values){
39 sun+=val.get();
40 count++;
41 }
42 int averscore=(int)sun/count;
43 context.write(key, new IntWritable(averscore));
44 }
45
46 }
47
48 public int run(String[] args) throws Exception{
49 Job job=new Job(getConf());
50 job.setJarByClass(Score_Process.class);
51 job.setJobName("Score_Process");
52
53 job.setOutputKeyClass(Text.class);
54 job.setOutputValueClass(IntWritable.class);
55
56 job.setMapperClass(Map.class);
57 //job.setCombinerClass(Reduce.class);
58 job.setReducerClass(Reduce.class);
59
60 job.setInputFormatClass(TextInputFormat.class);
61 job.setOutputFormatClass(TextOutputFormat.class);
62
63 FileInputFormat.setInputPaths(job, new Path(args[0]));
64 FileOutputFormat.setOutputPath(job, new Path(args[1]));
65 boolean success=job.waitForCompletion(true);
66
67 return success?0:1;
68 }
69
70 public static void main(String[] args)throws Exception{
71 int ret=ToolRunner.run(new Score_Process(), args);
72 System.exit(ret);
73 }
74
75 }
