Reputation: 169
I want to run the code described in this tutorial in order to customize the output format in Hadoop. More precisely, the tutorial shows two java files:
Well, what I did was to take the WordCount v1.0 of the MapReduce Tutorial (instead of using the WordCount showed in the tutorial) and add in the driver job.setOutputFormatClass(XMLOutputFormat.class);
and execute the hadoop app in this way:
/usr/local/hadoop/bin/hadoop com.sun.tools.javac.Main WordCount.java && jar cf wc.jar WordCount*.class && /usr/local/hadoop/bin/hadoop jar wc.jar WordCount /home/luis/Desktop/mytest/input/ ./output_folder
note: /home/luis/Desktop/mytest/input/
and ./output_folder
are the input and output folders, respectively.
Unfortunately, the terminal shows me the following error:
WordCount.java:57: error: cannot find symbol
job.setOutputFormatClass(XMLOutputFormat.class);
^
symbol: class XMLOutputFormat
location: class WordCount
1 error
Why? WordCount.java and XMLOutputFormat.java are stored in the same folder.
The following is my code.
WordCount
code:
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.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class WordCount {
public static class TokenizerMapper
extends Mapper<Object, Text, Text, IntWritable>{
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(Object key, Text value, Context context
) throws IOException, InterruptedException {
StringTokenizer itr = new StringTokenizer(value.toString());
while (itr.hasMoreTokens()) {
word.set(itr.nextToken());
context.write(word, one);
}
}
}
public static class IntSumReducer
extends Reducer<Text,IntWritable,Text,IntWritable> {
private IntWritable result = new IntWritable();
public void reduce(Text key, Iterable<IntWritable> values,
Context context
) throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
result.set(sum);
context.write(key, result);
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
Job job = Job.getInstance(conf, "word count");
job.setJarByClass(WordCount.class);
job.setMapperClass(TokenizerMapper.class);
job.setCombinerClass(IntSumReducer.class);
job.setReducerClass(IntSumReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
job.setOutputFormatClass(XMLOutputFormat.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
XMLOutputFormat
code:
import java.io.DataOutputStream;
import java.io.IOException;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class XMLOutputFormat extends FileOutputFormat<Text, IntWritable> {
protected static class XMLRecordWriter extends RecordWriter<Text, IntWritable> {
private DataOutputStream out;
public XMLRecordWriter(DataOutputStream out) throws IOException{
this.out = out;
out.writeBytes("<Output>\n");
}
private void writeStyle(String xml_tag,String tag_value) throws IOException {
out.writeBytes("<"+xml_tag+">"+tag_value+"</"+xml_tag+">\n");
}
public synchronized void write(Text key, IntWritable value) throws IOException {
out.writeBytes("<record>\n");
this.writeStyle("key", key.toString());
this.writeStyle("value", value.toString());
out.writeBytes("</record>\n");
}
public synchronized void close(TaskAttemptContext job) throws IOException {
try {
out.writeBytes("</Output>\n");
} finally {
out.close();
}
}
}
public RecordWriter<Text, IntWritable> getRecordWriter(TaskAttemptContext job) throws IOException {
String file_extension = ".xml";
Path file = getDefaultWorkFile(job, file_extension);
FileSystem fs = file.getFileSystem(job.getConfiguration());
FSDataOutputStream fileOut = fs.create(file, false);
return new XMLRecordWriter(fileOut);
}
}
Upvotes: 0
Views: 856
Reputation: 97
We will need to add the XMLOutputFormat.jar file to the HADOOP_CLASSPATH first for the driver code to find it. And pass it in -libjars option to be added to classpath of the map and reduce jvms.
export HADOOP_CLASSPATH=$HADOOP_CLASSPATH:/abc/xyz/XMLOutputFormat.jar
yarn jar wordcount.jar com.sample.test.Wordcount
-libjars /path/to/XMLOutputFormat.jar
/lab/mr/input /lab/output/output
Upvotes: 1
Reputation: 590
You need to either add package testpackage;
at the beginning of your WordCount
class
or
import testpackage.XMLOutputFormat;
in your WordCount
class.
Because they are in the same directory, it doesn't imply they are in the same package.
Upvotes: 1