java - IDP Initiated SSO Implementation in existing App -

i have existing application , of sudden have been given task implement idp initiated sso. there url idp clicking on asks me login idp provided credentials, after success login route moves our application , task start identify user , give proper access. have certificate provided our idp. how can achieve this? application spring mvc java application.i using jboss 7. havent done similar thing before. can please give step step clear picture on this? saw spring saml extension couldnt understand integrate existing app. in regard highly appreciated.

idp-initiated sso

idp-initiated sso post binding

1. if user not have valid local security context @ idp, @ point user challenged supply credentials idp site, idp.example.org.
2. the user provides valid credentials , local logon security context created user @ idp.
3. the user selects menu option or link on idp request access sp web site, sp.example.com. causes idp's single sign-on service called.
4. the single sign-on service builds saml assertion representing user's logon security context. since post binding going used, assertion digitally signed before placed within saml message. message placed within html form hidden form control named samlresponse. (if convention identifying specific application resource @ sp supported @ idp , sp, resource url @ sp encoded form using hidden form control named relaystate.) single sign-on service sends html form browser in http response. ease-of-use purposes, html form typically contain script code automatically post form destination site.
5. the browser, due either user action or execution of “auto-submit” script, issues http post request send form sp's assertion consumer service. service provider's assertion consumer service obtains message html form processing. digital signature on saml assertion must first validated , assertion contents processed in order create local logon security context user @ sp. once completes, sp retrieves relaystate data (if any) determine desired application resource url , sends http redirect response browser directing access requested resource (not shown).
6. an access check made establish whether user has correct authorization access resource. if access check passes, resource returned browser.

see saml-tech-overview-2.0

so if implementing sp, have follow steps 5 , 6 otherwise 1 - 4.

for implementation use opensaml if not working spring saml extension.