我是java和hadoop的新手。我遵循这个教程(https://developpaper.com/simple-java-hadoop-mapreduce-program-calculate-average-score-from-package-to-submit-and-run/). 我在提供输入时做了一些小修改。请参考代码。
public class Score {
public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {
// Implement map function
public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
// Convert the data of the input plain text file to string
String line = value.toString();
// Split the input data into rows first
StringTokenizer tokenizerArticle = new StringTokenizer(line, "\n");
// Process each line separately
while (tokenizerArticle.hasMoreElements()) {
// Line by space
StringTokenizer tokenizerLine = new StringTokenizer(tokenizerArticle.nextToken());
String strName = tokenizerLine.nextToken(); // student name
// section
String strScore = tokenizerLine.nextToken(); // grade section
Text name = new Text(strName);
int scoreInt = Integer.parseInt(strScore);
// Output name and score
context.write(name, new IntWritable(scoreInt));
}
}
}
public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> {
// Implement reduce function
public void reduce(Text key, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
int sum = 0;
int count = 0;
Iterator<IntWritable> iterator = values.iterator();
while (iterator.hasNext()) {
sum += iterator.next().get(); // calculate the total score
count++; // count the total number of accounts
}
Integer average = (int) sum / count; // calculate the average score
context.write(key, new IntWritable(average));
}
}
public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
// TODO Auto-generated method stub
Configuration conf = new Configuration();
// " localhost:9000 "It needs to be set according to the actual
// situation
conf.set("mapred.job.tracker", "localhost:9000");
// Input directory and output directory in an HDFS file system
String[] ioArgs = new String[] { "score.txt", "output" };
String[] otherArgs = new GenericOptionsParser(conf, ioArgs).getRemainingArgs();
if (otherArgs.length != 2) {
System.err.println("Usage: Score Average <in> <out>");
System.exit(2);
}
Job job = new Job(conf, "Score Average");
job.setJarByClass(Score.class);
// Set map, combine and reduce processing classes
job.setMapperClass(Map.class);
job.setCombinerClass(Reduce.class);
job.setReducerClass(Reduce.class);
// Set output type
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
// The input data set is divided into small data blocks splites to
// provide a RecordReder implementation
job.setInputFormatClass(TextInputFormat.class);
// Provide an implementation of recordwriter, responsible for data
// output
job.setOutputFormatClass(TextOutputFormat.class);
// Set input and output directories
FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
在那里,我使用maven在eclips中尝试了程序源代码。我为pom.xml文件添加了依赖项,如下所示。
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>mapreducedemocode</groupId>
<artifactId>mapreducedemocode</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>mapreducedemocode</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-client</artifactId>
<version>2.7.3</version>
</dependency>
</dependencies>
</project>
但当我运行代码时,它会给出以下异常。
Exception in thread "main" java.lang.UnsatisfiedLinkError: org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Ljava/lang/String;I)Z
at org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Native Method)
有人能帮我解决这个问题吗。请注意,我将输入文件('score.txt)添加到项目中,并通过将参数添加为'score.txt output'来设置运行配置。提供论据有什么问题吗。
暂无答案!
目前还没有任何答案,快来回答吧!