I am using Cloudera Hadoop, I want to perform Spatial Analytics and need to connect to quantum GIS(QGIS) for geospatial purposes. I need to know how to connect both QGIS and Hadoop. Also is there any other way to connect any other GIS systems except ARCGIS?
There are a number of free and open-source offerings you can use to achieve your goals.
From the list of LocationTech projects, I'd note that GeoJinni (formerly Spatial Hadoop), GeoMesa, and GeoTrellis all work with Hadoop or distributed databases like Accumulo or Cassandra.
More generally, since working with Hadoop means using Java, I'd recommend the GeoTools project for processing geo/gis data on the JVM. GeoTools is used as a library for GeoServer to publish geospatial data using open standards. GeoServer and MapServer are two of the open alternatives for Arc server products.
As you are looking for alternatives to Arc desktop products, QGIS and OpenJump are both options.
As a concrete, small examples, I've used the GeoTools library to read shapefiles from HDFS for ingest into GeoMesa with no problems. Previously, I have looked at serving up geotiffs hosted on HDFS/S3 through GeoServer, and there were a few small changes necessary to wire that up through the stack, but I was able to do it since all the software involved is open-source.
(In full-disclosure, I work on GeoMesa, participate quite a bit with LocationTech projects and some with GeoTools/GeoServer.)