Passing parameters to map function in Hadoop

Question

I am new to Hadoop. I want to access a command line argument from main function(Java program) inside the map function of the mapper class. Please suggest ways to do this.

Answer 1

Hadoop 0.20, introduced new MR API, there is not much functionality difference between the new (o.a.h.mapreduce package) and old MR API (o.a.h.mapred) except that data can be pulled within the mappers and the reducers using the new API. What Arnon is mentioned is with the old API.

Check this article for passing the parameters using the new and old API.

Answer 2

You can pass parameters by hanging them on the Configuration

 JobConf job = new JobConf(new Configuration(), TheJob.class);
 job.setLong("Param Name",longValue)

The Configuration class has few set methods (Long, Int, Strings etc.) so you can pass parameters of several types. In the map job you can get the configuration from the Context (getConfiguration)