我想运行本教程中描述的代码,以便在hadoop中自定义输出格式。更准确地说,本教程显示了两个java文件:
wordcount:是wordcount java应用程序(类似于此链接中mapreduce教程的wordcountv1.0)
xmloutputformat:java类,它扩展fileoutputformat并实现自定义输出的方法。
我所做的是使用mapreduce教程的wordcountv1.0(而不是使用教程中显示的wordcount)并添加驱动程序 job.setOutputFormatClass(XMLOutputFormat.class);
并按以下方式执行hadoop应用程序: /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
注: /home/luis/Desktop/mytest/input/
以及 ./output_folder
分别是输入和输出文件夹。
不幸的是,终端显示以下错误: WordCount.java:57: error: cannot find symbol job.setOutputFormatClass(XMLOutputFormat.class); ^ symbol: class XMLOutputFormat location: class WordCount 1 error
为什么?wordcount.java和xmloutputformat.java存储在同一文件夹中。
下面是我的代码。 WordCount
代码:
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` 代码:
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);
}
}
2条答案
按热度按时间to94eoyn1#
你要么
package testpackage;
在你人生的开始WordCount
班或
import testpackage.XMLOutputFormat;
在你的WordCount
班级。因为它们在同一个目录中,这并不意味着它们在同一个包中。
kulphzqa2#
我们需要先将xmloputformat.jar文件添加到hadoop\u类路径中,驱动程序代码才能找到它。并在-libjars选项中传递它,以添加到Map的类路径中并减少JVM。