Extracting Attribute Query from request

Hello,
 
I am trying to generate authReponse using openSAML that will be sent to SP for idp-initiated sso in a servlet. In turns SP will send me Attribute Query. I need to know how Attribute Query string is posted by SP. that is can i get Attribute Query as string from parameter SAMLRequest. Will this parameter present in request sent by SP.

 
Thanks