如何在Hortonworks沙盒Hadoop平台中运行mapreduce作业

Question

I am new in Hadoop. I have installed the oracle virtual box for and mounted the image of hortonworks sandbox in the virtual machine.also i have written the wordcount program in eclipse and trying to run that in the virtual machine. But I am getting an exception tree. I am posting the program and the error tree also.

public class WordCount {

public static class Map extends MapReduceBase implements
        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,
            OutputCollector<Text, IntWritable> output, Reporter reporter)
            throws IOException {
        String line = value.toString();
        StringTokenizer tokenizer = new StringTokenizer(line);
        while (tokenizer.hasMoreTokens()) {
            word.set(tokenizer.nextToken());
            output.collect(word, one);
        }
    }
}

public static class Reduce extends MapReduceBase implements
        Reducer<Text, IntWritable, Text, IntWritable> {
    public void reduce(Text key, Iterator<IntWritable> values,
            OutputCollector<Text, IntWritable> output, Reporter reporter)
            throws IOException {
        int sum = 0;
        while (values.hasNext()) {
            sum += values.next().get();
        }
        output.collect(key, new IntWritable(sum));
    }
}

public static void main(String[] args) throws IOException {
    JobConf conf = new JobConf(WordCount.class);
    conf.setJobName("wordcount");

    conf.setOutputKeyClass(Text.class);
    conf.setOutputValueClass(IntWritable.class);

    conf.setMapperClass(Map.class);
    conf.setCombinerClass(Reduce.class);
    conf.setReducerClass(Reduce.class);

    conf.setInputFormat(TextInputFormat.class);
    conf.setOutputFormat(TextOutputFormat.class);

    FileInputFormat.setInputPaths(conf, new Path(args[0]));
    FileOutputFormat.setOutputPath(conf, new Path(args[1]));

    JobClient.runJob(conf);

}

}

[hue@sandbox`]$hadoop jar/usr/lib/wordcount.jar wordcount[-m][-r]

Exception in thread main java.lang.NoClassDefFoundError:jar/usr/lib/wordcount/jar

caused by:java.lang.ClassNotFoundException:jar.usr.lib.wordcount.jar at java.net.URLClassLoader$1.run(URLlassLoader.java:202) at java.security.AccessController.doPriviledged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Laucher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

could not find the main class:jar/usr/lib/wordcount.jar

i am using the Hortonworks+Sandbox+1.3+VirtualBox+RC6 this version on a 64 bit machine .

Answer 1

You're not invoking hadoop correctly, you're missing a space, as well as args. Try

hadoop jar /usr/lib/wordcount.jar WordCount <the path to your input file on HDFS> <the path to your output directory on HDFS>

If you get another class not found, try using the full class name of WordCount (eg, com.mysite.WordCount). I can't see what package it's in.