When you say “connecting Hadoop and NiFi” are you referring to specifically interacting with data in HDFS or HBase? NiFi provides processors by default for consuming from and writing data to HDFS (GetHDFS , PutHDFS , ListHDFS , FetchHDFS , etc.) and HBase (GetHBase , PutHBaseCell , PutHBaseJSON ) instances. There are also a couple of tutorials which discuss the process to configure those resources .
If these resources do not help and you have more specific questions, we will be happy to try and answer those.