[英]Hadoop Mapreduce word count Program
我是Hadoop的新手。 下面是我的代码。 运行Jar时出现以下错误消息。
输入文件(wordcount.txt)=>此文件存储在“ /home/cloudera/SK_JAR/jsonFile/wordcount.txt”路径中
您好Hadoop,再见Hadoop。
package com.main;
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.LongWritable;
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.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
public class WordCount {
public static class Map extends Mapper {
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
String line = value.toString();
StringTokenizer tokenizer = new StringTokenizer(line);
while (tokenizer.hasMoreTokens()) {
word.set(tokenizer.nextToken());
context.write(word, one);
}
}
}
public static class Reduce extends Reducer {
public void reduce(Text key, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
context.write(key, new IntWritable(sum));
}
}
public static void main(String[] args) throws IllegalArgumentException, IOException, ClassNotFoundException, InterruptedException {
// TODO Auto-generated method stub
Configuration conf = new Configuration();
Job job = new Job(conf, "wordcount");
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
job.setMapperClass(Map.class);
job.setReducerClass(Reduce.class);
job.setInputFormatClass(TextInputFormat.class);
job.setOutputFormatClass(TextOutputFormat.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
// job.waitForCompletion(true);
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
以下是错误消息。 有人可以帮我吗?
让我知道你们是否需要更多细节。
hadoop jar Wordcount.jar WordCount '/home/cloudera/SK_JAR/jsonFile/wordcount.txt' output
Error in laoding args file.java.io.FileNotFoundException: WordCount (No such file or directory)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:146)
at java.io.FileInputStream.<init>(FileInputStream.java:101)
at com.main.mainClass.main(mainClass.java:28)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
at org.apache.hadoop.util.RunJar.main(RunJar.java:136)
hadoop jar Wordcount.jar WordCount
您的主类是com.main
包的一部分,因此需要com.main.WordCount
来启动您的类。
您可以将JAR文件作为ZIP文件打开,以验证是否可以在其中找到com/main/WordCount$Map.class
。 如果不存在,则说明Eclipse生成的JAR错误。
我可能建议您学习Maven,Gradle或SBT来构建JAR而不是IDE。 在生产中,这些是通常用于捆绑Hadoop JAR文件的工具。
似乎您的可运行jar文件未提及主类文件。
如果使用Eclipse创建jar文件,请按照以下步骤创建Wordcount.jar。
右键单击Project-> Export JAR文件->单击Next->取消选中所有其他资源。 然后提供导出.jar文件的路径->单击下一步->保持选项处于选中状态->单击下一步并完成。 参考
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