Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/cli2/Option

　　今天，在做canopy算法实例时，遇到这个问题，所以记录下来。下面是源码：

　　

package czx.com.mahout;


import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
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.output.SequenceFileOutputFormat;
import org.apache.hadoop.util.ToolRunner;
import org.apache.mahout.common.AbstractJob;
import org.apache.mahout.math.RandomAccessSparseVector;
import org.apache.mahout.math.VectorWritable;

public class TextVecWrite extends AbstractJob {

    public static void main(String[] args) throws Exception {
        ToolRunner.run(new Configuration(), new TextVecWrite(), args);
    }
    
    /**
     * TextVecWriterMapper
     * @author czx
     *;
     */
    public static class TextVecWriterMapper extends Mapper<LongWritable, Text, LongWritable,VectorWritable >{
        @SuppressWarnings("unchecked")
        @Override
        protected void map(LongWritable key, Text value,
                @SuppressWarnings("rawtypes") org.apache.hadoop.mapreduce.Mapper.Context context)
                        throws IOException, InterruptedException {
            String[] split = value.toString().split("\\s{1,}");
            RandomAccessSparseVector vector = new RandomAccessSparseVector(split.length);
            for(int i=0;i<split.length;++i){
                vector.set(i, Double.parseDouble(split[i]));
            }
            VectorWritable vectorWritable = new VectorWritable(vector);
            context.write(key, vectorWritable);
        }
    }
    
    /**
     * TextVectorWritableReducer
     * @author czx
     *
     */
    public static class TextVectorWritableReducer extends Reducer<LongWritable, VectorWritable, LongWritable , VectorWritable >{
        @Override
        protected void reduce(LongWritable arg0, Iterable<VectorWritable> arg1,
                Context arg2)
                throws IOException, InterruptedException {
            for(VectorWritable v:arg1){
                arg2.write(arg0, v);
            }
        }
    }
    
    @Override
    public int run(String[] arg0) throws Exception {
        addInputOption();
        addOutputOption();
        if(parseArguments(arg0)==null){
            return -1;
        }
        Path input = getInputPath();
        Path output = getOutputPath();
        Configuration conf = getConf();

        Job job = new Job(conf,"textvectorWritable with input:"+input.getName());
        job.setOutputFormatClass(SequenceFileOutputFormat.class);
        job.setMapperClass(TextVecWriterMapper.class);
        job.setReducerClass(TextVectorWritableReducer.class);
        job.setMapOutputKeyClass(LongWritable.class);
        job.setOutputValueClass(VectorWritable.class);
        job.setOutputKeyClass(LongWritable.class);
        job.setOutputValueClass(VectorWritable.class);
        job.setJarByClass(TextVecWrite.class);
        
        FileInputFormat.addInputPath(job, input);
        SequenceFileOutputFormat.setOutputPath(job, output);
        
        if(!job.waitForCompletion(true)){
            throw new InterruptedException("Canopy Job failed processing "+input);
        }
        return 0;
    }
}

　　将程序编译打包成JAR并运行如下：

　　

 hadoop jar ClusteringUtils.jar czx.com.mahout.TextVecWrite -i /user/hadoop/testdata/synthetic_control.data -o /home/czx/1

　　但出现如下错误：

　　

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/cli2/Option
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:270)
	at org.apache.hadoop.util.RunJar.main(RunJar.java:205)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.cli2.Option
	at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
	... 3 more

　　最后，发现是将mahout根目录下的相应的jar包复制到hadoop-2.4.1/share/hadoop/common/lib文件夹下时，少复制了mahout-core-0.9-job.jar，于是复制mahout-core-0.9-job.jar后，重新启动hadoop即可。