Export data from hadoop to elastic using java

I have to do some pre-processing( denormalization) of hadoop tables before inserting it to ElasticSearch. My plan is to use java to do this task. Could you please guide me how to do this, Or please share some doc link etc.,

There is Elasticsearch for Apache Hadoop - maybe this can help you. If not, please ask some more specific questions what problems you are encountering. Thank you!