我无法在 job.waitforcompletion(boolean) 子句中编译我的 DriverClass。它给了我一个 NoClassFoundException。如果我捕捉到异常，run 方法会抛出它期望一个 int 值的错误。我正在使用 MapReduce New API。谁能提出问题所在：
import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.filecache.DistributedCache;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.util.GenericOptionsParser;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.KeyValueTextInputFormat;
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 Dist_Driver extends Configured implements Tool {
public int run(String args[]) throws IOException, InterruptedException {
// Configuration phase
// Configuration conf=new Configuration();
Job job = new Job(new Configuration());
job.setJarByClass(Dist_Driver.class);
// Mapper Reducer InputFormat
job.setInputFormatClass(FileInputFormat.class);
// Mapper and Reducer Class
job.setMapperClass(Dist_Mapper.class);
job.setReducerClass(DistCache_Reducer.class);
job.setOutputFormatClass(TextOutputFormat.class);
job.setInputFormatClass(KeyValueTextInputFormat.class);
// set FileInputOutput
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
// setting number of reduce tasks and submit it
job.setNumReduceTasks(2);
// Lets check if the file exist
File f1 = new File("/home/hdfs/trials_mapreduce_progams/emp_id");
if (f1.exists())
System.out.println("The Files Exists");
else
System.out.println("The File doesnot exist");
URI path1;
try {
path1 = new URI(
"/home/hdfs/trials_mapreduce_progams/emp_lookup.txt");
DistributedCache.addCacheFile(path1, job.getConfiguration());
} catch (URISyntaxException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (job.waitForCompletion(true))
return 0;
else
return 1;
}
public static void main(String[] args) throws Exception {
int exitcode = ToolRunner.run(new Dist_Driver(), args);
System.exit(exitcode);
}
}