mapreduce课堂测试结果

package mapreduce;
import java.io.IOException;
import java.util.StringTokenizer;
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.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class WordCount {
public static void main(String[] args) throws IOException,ClassNotFoundException,InterruptedException {
Job job = Job.getInstance();
job.setJobName("WordCount");
job.setJarByClass(WordCount.class);
job.setMapperClass(doMapper.class);
job.setReducerClass(doReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
Path in = new Path("hdfs://localhost:9000/a/buyer_favorite1");
Path out = new Path("hdfs://localhost:9000/a/out");
FileInputFormat.addInputPath(job,in);
FileOutputFormat.setOutputPath(job,out);
System.exit(job.waitForCompletion(true)?0:1);
}
public static class doMapper extends Mapper{
public static final IntWritable one = new IntWritable(1);
public static Text word = new Text();
@Override
protected void map(Object key, Text value, Context context)
throws IOException,InterruptedException {
StringTokenizer tokenizer = new StringTokenizer(value.toString(),"  ");
word.set(tokenizer.nextToken());
context.write(word,one);
}
}
public static class doReducer extends Reducer{
private IntWritable result = new IntWritable();
@Override
protected void reduce(Text key,Iterable values,Context context)
throws IOException,InterruptedException{
int sum = 0;
for (IntWritable value : values){
sum += value.get();
}
result.set(sum);
context.write(key,result);
}
}
}

题目：

在/home/hadoop/data/mapreduce1/a下面创建buyer_mapreduce1.txt文件并向其中添加一部分数据，通过命令

cd /usr/local/hadoop

切换至/usr/local/hadoop文件夹下将刚才创建的文本文件通过命令

./bin/hdfs dfs -put /home/hadoop/data/mapreduce1/a/buyer_mapreduce1.txt a

上传至hadoop文件夹下的a文件夹下并对其进行后续操作；

运行截图：

经验总结：在linux的文本文件中相邻行数据之间如果存在空行就会报错，去除空行则错误消失；