我正在尝试运行 WordCount map/reduce 作业的示例代码。我在 Hadoop 1.2.1 上运行它。我正在从我的 Eclipse 运行它。这是我尝试运行的代码:
package mypackage;
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.Reducer.Context;
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<LongWritable, Text, Text, IntWritable> {
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<Text, IntWritable, Text, IntWritable> {
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 Exception {
Configuration conf = new Configuration();
conf.set("mapred.job.tracker", "maprfs://,y_address");
conf.set("fs.default.name", "hdfs://my_address");
Job job = new Job(conf, "wordcount");
job.setJarByClass(WordCount.class);
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);
}
}
不幸的是,运行此代码最终会出现以下错误:
2004 年 13 月 11 日 13:27:53 信息 mapred.JobClient:任务 ID:尝试_201310311611_0005_m_000000_0,状态:失败 java.lang.RuntimeException:java.lang.ClassNotFoundException:com.rf.hadoopspikes.WordCount$Map 在 org.apache.hadoop .conf.Configuration.getClass(Configuration.java:857) 在 org.apache.hadoop.mapreduce.JobContext.getMapperClass(JobContext.java:199) 在 org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:718 ) 在 org.apache.hadoop.mapred.MapTask.run(MapTask.java:364) 在 org.apache.hadoop.mapred.Child$4.run(Child.java:255) 在 java.security.AccessController.doPrivileged(Native方法)在 javax.security.auth.Subject.doAs(Subject.java:415) 在 org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190) 在 org.apache.hadoop.mapred.Child.main (儿童.java:249)
我知道找不到 WordClass,但我不知道如何进行这项工作。有任何想法吗?