hadoop 之wordcount,
除了这个之外当然还看了几个demo, 把wordcount放到最后,打算单独实现一遍。
最后还是在继承类的泛型的地方存在一些盲区,日后补上。
代码:
package wordcount;
import java.io.IOException;
import java.util.StringTokenizer;
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.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
//import org.apache.hadoop.mapreduce.Reducer.Context;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
public class WordCount {
public static class Map extends Mapper<Object, Text, Text, IntWritable>{
private static Text line = new Text();//每行数据
private static IntWritable one = new IntWritable(1);
private static Text word = new Text();
public void map(Object key, Text value, Context context) throws IOException, InterruptedException{
line = value;
// context.write(line, new Text(""));one
StringTokenizer itr = new StringTokenizer(value.toString());
while(itr.hasMoreElements()){
word.set(itr.nextToken());
context.write(word, one);
}
}
}
public static class Reduce extends Reducer<Text,IntWritable,Text,IntWritable> {
public void reduce(Text key,Iterable<IntWritable> values, Context context) throws IOException, InterruptedException{
// context.write(key, new Text(""));
IntWritable res = new IntWritable();
int sum = 0;
for(IntWritable value: values){
sum+=value.get();//熟悉下intwritable方法,属性
}
res.set(sum);
context.write(key, res);
}
}
public static void main(String args[]) throws IOException, ClassNotFoundException, InterruptedException{
Configuration conf = new Configuration();
conf.set("mapred.job.tracker", "127.0.0.1:9000");
String[] ioArgs=new String[]{"hdfs://localhost:9000/count_in","hdfs://localhost:9000/count_out"};
//??
String[] otherArgs = new GenericOptionsParser(conf,ioArgs).getRemainingArgs();
if(otherArgs.length!=2){
System.err.println("xx");
System.exit(2);//2是什么状态
}
Job job = new Job(conf,"data dedup");
job.setJarByClass(WordCount.class);
job.setMapperClass(Map.class);
job.setCombinerClass(Reduce.class);
job.setReducerClass(Reduce.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
System.exit(job.waitForCompletion(true)?0:1);
}
}
截图:
文本
结果:
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