OAuth 2.0 using Grails Part – 2

Obtain accessToken from refreshToken

In the previous article OAuth 2.0 using Grails Part – 1 I have given a detailed explanation regarding user authentication using OAuth 2.0. In this article i will explain how you can obtain access_token from the refresh_token. Please refer to step(3) of part – 1 of this article where we obtained a JSON of the following format :

{
"access_token": {access_token},
"token_type": "Bearer",
"expires_in": 3600,
"refresh_token": {refresh_token},
"id_token": {id_token}
}

You need to persist the refresh_token in some database because access_token which we have got in the JSON is only valid for 1 hour. A fresh access_token can be obtained with the help of refresh_token. Following method will take persisted refresh_token as a parameter and will return a fresh access_token.

String getLatestAccessToken(String refreshToken) {
 String latestToken = ""
 def http = new HTTPBuilder('http://localhost:8080/')
 http.request(POST) {
 uri.path = 'https://accounts.google.com/o/oauth2/token'
 requestContentType = "application/x-www-form-urlencoded"
 body = [
client_id: "{Client ID}",
client_secret: "{Client Secret}",
 grant_type: "refresh_token",
 refresh_token: refreshToken
 ]
 response.success = { resp, json ->
 latestToken = json.access_token
 }
 }
 return latestToken
 }

In the above code response.success closure contains parameter json which contains the response in the following format:

{
"access_token": {access_token},
"token_type": "Bearer",
"expires_in": 3600,
"id_token": {id_token}
}

From this JSON we are obtaining access_token which is again valid for 1 hour only.