hadoop|MapReduce实验——学生总成绩报表，学生平均成绩 hadoop|big|data|mapreduce

学生总成绩报表
【hadoop|MapReduce实验——学生总成绩报表，学生平均成绩】
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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 { @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 { protected void reduce(Text key,Iterable values,Context context) throws IOException, InterruptedException { //获取键值对集合遍历对象 Iterator 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 { protected void reduce(Text key,Iterable values,Context context) throws IOException, InterruptedException { //获取键值对集合遍历对象 Iterator 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); ; } }