MapReduce实验——学生总成绩报表，学生平均成绩

学生总成绩报表

Map类

package StudentScore_06;

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

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

public class MyMap extends
        Mapper<LongWritable,Text, Text, IntWritable> {
    @Override
    protected void map(LongWritable key,Text value,Context context) throws IOException, InterruptedException {
        //读取一行数据
        String val = value.toString();
        //把读取的数据以换行作为分隔符
        StringTokenizer stringTokenizer = new StringTokenizer(val,"\n");
        while (stringTokenizer.hasMoreElements()){
            StringTokenizer tmp = new StringTokenizer(stringTokenizer.nextToken());
            //对读取的一行的名称和成绩进行切分并写入到context对象中
            String username = tmp.nextToken();
            String score = tmp.nextToken();
            context.write(new Text(username),new IntWritable(Integer.valueOf(score)));
        }
    }
}

Reduce 类

package StudentScore_06;

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

import java.io.IOException;
import java.util.Iterator;

public class MyReduce extends Reducer<Text, IntWritable,Text,IntWritable> {
    protected void reduce(Text key,Iterable<IntWritable> values,Context context) throws IOException, InterruptedException {
        //获取键值对集合 遍历对象
        Iterator<IntWritable> iterator = values.iterator();
        int sum = 0;
        //循环获取相同键的所有值并进行计算和
        while(iterator.hasNext()){
            int v = iterator.next().get();
            sum+=v;
        }
        context.write(key,new IntWritable(sum));
    }
}

Reduce类(求学生平均成绩)

package StudentAvgScore_07;

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

import java.io.IOException;
import java.util.Iterator;

public class MyReduce extends Reducer<Text, IntWritable,Text,IntWritable> {
    protected void reduce(Text key,Iterable<IntWritable> values,Context context) throws IOException, InterruptedException {
        //获取键值对集合 遍历对象
        Iterator<IntWritable> iterator = values.iterator();
        int count = 0;
        int sum = 0;
        //循环获取相同键的所有值并进行计算和
        while(iterator.hasNext()){
            int v = iterator.next().get();
            sum+=v;
            count++;
        }
        int avg = sum/count;
        context.write(key,new IntWritable(avg));
    }
}

Job类

package StudentScore_06;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
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.io.Text;
import java.io.IOException;

public class TestJob {
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration conf = new Configuration();
        //1、获取作业对象
        Job job = Job.getInstance(conf);
        //2、设置主类
        job.setJarByClass(TestJob.class);
        //3、设置job参数
        job.setMapperClass(MyMap.class);
        job.setReducerClass(MyReduce.class);
        //4 set map reduce output type
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        //5、设置job输入输出
        FileInputFormat.setInputPaths(job,new Path("file:///simple/source.txt"));
        FileOutputFormat.setOutputPath(job,new Path("file:///simple/output"));
        //6 commit job
        System.out.println(job.waitForCompletion(true) ? 0 : 1);;
    }
}