Google Tasks service object for a User who is already authenticated with oAuth2 (Grails/Java) -

i trying google tasks service object has authorised credentials in order can pull tasks user has registered , logged-in (oauth2) our web application via google apps marketplace.

unfortunately receiving 401 - authorization - login required. can tell me going wrong?

here code gettasksservice() method:

def httptransport = new nethttptransport() def jsonfactory = new jacksonfactory();  def clientid = google_client_id def clientsecret = google_secret def applicationname = application_name  def tokenresponse = (tokenresponse) googleappsnewoauthservice.getgoogleresponse() def credential = new googlecredential.builder()                                      .setjsonfactory(jsonfactory)                                      .settransport(httptransport)                                      .setclientsecrets(clientid, clientsecret)                                      .build()                                      .setfromtokenresponse(tokenresponse)  def service = new com.google.api.services.tasks.tasks.builder(httptransport, jsonfactory, credential)                                                      .setapplicationname(applicationname)                                                      .build() return service 

the code googleappsnewoauthservice.getgoogleresponse() method:

public jsonelement getgoogleresponse() {     def session = requestcontextholder.currentrequestattributes().getsession()     token googleaccesstoken = (token) session[oauthservice.findsessionkeyforaccesstoken('google')]      log.info "google access token: ${googleaccesstoken.token}"      if(googleaccesstoken == null) {         return null     }      def googleresource = oauthservice.getgoogleresource(googleaccesstoken, "https://www.googleapis.com/oauth2/v1/userinfo" )     def googleresponse = json.parse(googleresource?.getbody())      return googleresponse } 

... , resulting googlejsonresponseexception:

{   "code" : 401,   "errors" : [ {     "domain" : "global",     "location" : "authorization",     "locationtype" : "header",     "message" : "login required",     "reason" : "required"   } ],   "message" : "login required" }  @ com.google.api.client.googleapis.json.googlejsonresponseexception.from(googlejsonresponseexception.java:145)