Is it possible with Hibernate to associate 2 java objects but still there is no relationship between the two entities in database? If yes, then please point me to appropriate references on how to do this.

In my case I have got a "location" entity which I want to be common for "Users" & "Contacts" in my application. For this one option that comes to my mind is to have unidirectional many-to-one relationship between "User" & "Location" and "Contact" & "Location". I am looking for an option in which these is no RI constraint between tables and yet I achieve cascading between my objects

Unfortunately, you're going to need some type of foreign key. You may not need the actual constraint, but a key pointing to the other table must be there.