One can use the HadoopUtil class to prepare a Hadoop MapReduce job

org.apache.mahout.common.HadoopUtil

public static Job prepareJob(Path inputPath,

Path outputPath,

Class<? extends InputFormat> inputFormat,

Class<? extends Mapper> mapper,

Class<? extends Writable> mapperKey,

Class<? extends Writable> mapperValue,

Class<? extends OutputFormat> outputFormat, Configuration conf) throws IOException {

Job job = new Job(new Configuration(conf));

Configuration jobConf = job.getConfiguration();

if (mapper.equals(Mapper.class)) {

throw new IllegalStateException(“Can’t figure out the user class jar file from mapper/reducer”);

}

job.setJarByClass(mapper);

job.setInputFormatClass(inputFormat);

jobConf.set(“mapred.input.dir”, inputPath.toString());

job.setMapperClass(mapper);

job.setMapOutputKeyClass(mapperKey);

job.setMapOutputValueClass(mapperValue);

job.setOutputKeyClass(mapperKey);

job.setOutputValueClass(mapperValue);

jobConf.setBoolean(“mapred.compress.map.output”, true);

job.setNumReduceTasks(0);

job.setOutputFormatClass(outputFormat);

jobConf.set(“mapred.output.dir”, outputPath.toString());

return job;

}

public static Job prepareJob(Path inputPath,

Path outputPath,

Class<? extends InputFormat> inputFormat,

Class<? extends Mapper> mapper,

Class<? extends Writable> mapperKey,

Class<? extends Writable> mapperValue,

Class<? extends Reducer> reducer,

Class<? extends Writable> reducerKey,

Class<? extends Writable> reducerValue,

Class<? extends OutputFormat> outputFormat,

Configuration conf) throws IOException {

Job job = new Job(new Configuration(conf));

Configuration jobConf = job.getConfiguration();

if (reducer.equals(Reducer.class)) {

if (mapper.equals(Mapper.class)) {

throw new IllegalStateException(“Can’t figure out the user class jar file from mapper/reducer”);

}

job.setJarByClass(mapper);

} else {

job.setJarByClass(reducer);

}

job.setInputFormatClass(inputFormat);

jobConf.set(“mapred.input.dir”, inputPath.toString());

job.setMapperClass(mapper);

if (mapperKey != null) {

job.setMapOutputKeyClass(mapperKey);

}

if (mapperValue != null) {

job.setMapOutputValueClass(mapperValue);

}

jobConf.setBoolean(“mapred.compress.map.output”, true);

job.setReducerClass(reducer);

job.setOutputKeyClass(reducerKey);

job.setOutputValueClass(reducerValue);

job.setOutputFormatClass(outputFormat);

jobConf.set(“mapred.output.dir”, outputPath.toString());

return job;

}