How to integrate with OpenFire XMPP server to receive roster info for users?
Solution 1:
All though the links provided by Manasi would work for you. However those links refers to user service plugin which has been depricated by openfire.
They recommend to use REST API plugin.
You'll see list of all plugins here.
You should read about retrieving user roster and their presence .
Solution 2:
You could try using the user service plugin of openfire that returns a host of information of the user as well as its rosters.
for documentation click here.
You can get the roster information by this url.