Using MultipleTextOutputFormat to control output filename in MapReduce

[Decimus Phostle]

Hello Folks,

I needed some help with using MultipleTextOutputFormat to control the
output filename in MapReduce.

Currently I am using it as shown below(or at
http://pastebin.com/gJxkdwRd). And it seems to work fine. However what
I am trying to change is the usage of the fields that get picked to
determine the filename.

Instead of hardcoding them to field[0] or field[3](as is the case in
the sample), I would like to pick this up (in some dynamic fashion)
from say, JobConf as field[jobConf.get("id.offset")] or
field[jobConf[get("date.offset")]. Does anyone here know how I could
go about doing this (or something to this effect i.e. it doesn't have
to be JobConf per se)?

Any pointers/suggestions/tips et al. would be most appreciated. Thanks.

PS:

1) Current usage of MultipleTextOutputFormat:

public class FooBarMultipleTextOutputFormat
extends MultipleTextOutputFormat<NullWritable, Text> {
        
        protected String generateFileNameForKeyValue(NullWritable key,
                                                                                
 Text value,
                                                                                
 String name) {
                String line = value.toString();

                //TODO: I would like to parameterize the field that is picked
                //here. Something akin to using JobConf in Mapper.
                //i.e. instead of hard-coding [3] or [0], I would like
                //to get it from JobConf(or some other configuration) in some 
fashion

                String date = (line.split("\t"))[3].substring(0,10);
                String id = (line.split("\t"))[0];

                String partitionNumber = String.format("%05d", 
ID.getPartitionNumber(id));

                return date + "/pn_" + partitionNumber;
        }
}

2) This is also an SO question here: http://goo.gl/FX7QN, if you would
rather answer it there. TIA.