Hi Sujitha,
For Sentiment analysis there has to be HANA text analysis engine which can help in retrieving the sentiment of the post. As such BAdi is available for calculating the sentiment even without hana. I haven't tried this part . There are lot of open source sentiment analysis api available. You can try that part via web services( Can't give surety ) or you can take an example of SAP code which is available in the z-class 
(cl_http_client=>create_by_url).
Good that you are trying this part which i didn't get chance to explore 
.
Note: If you are successful with it please do share .
Regards,
Bob.