Rakhi,
I've recently had to implement a custom InputFormat that's pretty basic
(every split is a list of integers basically).
You can check it out here http://github.com/codazzo/MultiRow
One guy also implemented a custom InputFormat and wrote about it on his
blog http://codedemigod.com/blog/?p=120
Hope that helps.
Antonio

On Fri, Jan 29, 2010 at 2:04 PM, Rakhi Khatwani <rkhatwani@gmail.com> wrote:

> Hi,
>         i have been trying to implement custom input and output formats. i
> was successful enough in creating an custom output format. but whn i call a
> mapreduce method which takes in a file, using custom input format, i get an
> exception.
> java.lang.NullPointerException
>  at Beans.Content.write(Content.java:54)
>  at
> org.apache.hadoop.io.serializer.WritableSerialization$WritableSerializer.serialize(WritableSerialization.java:90)
>  at
> org.apache.hadoop.io.serializer.WritableSerialization$WritableSerializer.serialize(WritableSerialization.java:77)
>  at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:613)
>  at
> CustomInputFormat.SampleCustomInputMap.map(SampleCustomInputMap.java:32)
>  at CustomInputFormat.SampleCustomInputMap.map(SampleCustomInputMap.java:1)
>  at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50)
>  at org.apache.hadoop.mapred.MapTask.run(MapTask.java:342)
>  at
> org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:138)
> 0 Hello World0 Hello World0 Hello World0
>
> id:: null media:: null url:: null content::null
>
> id:: null media:: null url:: null content::null
> java.io.IOException: Job failed!
>  at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:1232)
>  at
> CustomInputFormat.SampleCustomInputMapReduce.run(SampleCustomInputMapReduce.java:53)
>  at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
>  at
> CustomInputFormat.SampleCustomInputMapReduce.main(SampleCustomInputMapReduce.java:59)
>
>
> I have attached the following files
> Content => Custom object that implements writercomparible
> ContentInputFormatV2 => inputformat which implements
> SequenceFileInputFormat
> ContentRecordReader => implementation of RecordReader (Not required though,
> it should work w/o it i assume).
> SampleCustomInputMap => mapper class
> SampleCustomInputReduce => reducer class
> SampleCustomInputMapReduce => class which contains the main method and the
> job configurations.
> data and index => my inputfiles for the main function
> For the 1st record it works fine, but for next record and records after
> that, i get null. where could i go wrong??
> Regards,
> Raakhi
>