conf.get("map.input.file") returns null when using MultipleInputs in Hadoop 0.20

[Yuanyuan Tian]

I have a problem in getting the input file name in the mapper  when uisng
MultipleInputs. I need to use MultipleInputs to support different formats
for my inputs to the my MapReduce job. And inside each mapper, I also need
to know the exact input file that the mapper is processing. However,
conf.get("map.input.file") returns null. Can anybody help me solve this
problem? Thanks in advance.

public class Test extends Configured implements Tool{

        static class InnerMapper extends MapReduceBase implements
Mapper<Writable, Writable, NullWritable, Text>
        {
                ................
                ................

                public void configure(JobConf conf)
                {
                        String inputName=conf.get("map.input.file"));
                        .......................................
                }

        }

        public int run(String[] arg0) throws Exception {
                JonConf job;
                job = new JobConf(Test.class);
                ...........................................

                MultipleInputs.addInputPath(conf, new Path("A"),
TextInputFormat.class);
                MultipleInputs.addInputPath(conf, new Path("B"),
SequenceFileFormat.class);
                ...........................................
        }
}

Yuanyuan