public Roster getRoster() {
        try {
            return XMPPServer.getInstance().getRosterManager().getRoster(username);
        }
        catch (UserNotFoundException unfe) {
            Log.error(unfe.getMessage(), unfe);
            return null;
        }
    }
Returns the user's roster. A roster is a list of users that the user wishes to know
if they are online. Rosters are similar to buddy groups in popular IM clients.

@return the user's roster.
xmppserver/src/main/java/org/jivesoftware/openfire/user/User.java