Null pointer exception in Mapper initialization

[Mapred Learn]

 Hi,

I get error like:



java.lang.NullPointerException

                at
org.apache.hadoop.io<http://org.apache.hadoop.io.serializer.serializationfactory.ge/>
.serializer.SerializationFactory.getSerializer(SerializationFactory.java:73)

                at
org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:815)

                at
org.apache.hadoop.mapred.MapTask$NewOutputCollector.<init>(MapTask.java:549)

                at
org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:631)

                at org.apache.hadoop.mapred.MapTask.run(MapTask.java:315)

                at org.apache.hadoop.mapred.Child$4.run(Child.java:217)

                at java.security.AccessController.doPrivileged(Native
Method)

                at javax.security.auth.Subject.doAs(Subject.java:396)

                at
org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1063)

                at org.apache.hadoop.mapred.Child.main(Child.java:211)







My Mapper key/value are basic Writable types. Could somebody point me to
some clue as to why am I getting this error ?





Thanks,

-JJ