JDBC connectivity with Database

I am trying to connect to the DB table i created in my trial account from a servlet deployed on HCP.

Some of the help links state that only the web.xml needs to have the resource ref for the DefaultDB DataSource and then this should be working e.g.

SAP HANA Cloud Platform

However, adding the reference in the web.xml does not work. My understanding is, somewhere this DataSource must be defined. is the DefaultDB already defined and should be accessible as java:comp/env/jdbc/DefaultDB ? or additional steps are required?

Thanks

Amol