Classic ASP
Refresh GMail SMTP OAuth2 Access Token

Demonstrates how to refresh an access token for sending email via GMail (SMTP).
Chilkat Classic ASP Downloads

Classic ASP
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<%
success = 0

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' See Get GMail SMTP Access Token 
' for sample code showing how to obtain a GMail SMTP access token for desktop apps.

' It is assumed we previously obtained an OAuth2 access token for GMail (one with a scope for sending email).

set jsonToken = Server.CreateObject("Chilkat.JsonObject")
success = jsonToken.LoadFile("qa_data/tokens/_gmailSmtp.json")
If (success <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( "Failed to load _gmailSmtp.json") & "</pre>"
    Response.End
End If

' The access token JSON looks something like this:

' 	{ 
' 	 "access_token": "abac.Ci-ZabcdF37-NUrmSzxbHxTsMbtlN-uPfabcdAQN_2ekzj0s5ofCzRabcdTDMGaa2Q",
' 	 "token_type": "Bearer",
' 	 "expires_in": 3600,
' 	 "refresh_token": "1/lEe5abcdNJ77eOSDBabcdkQGVmDalkwabcdR2Hatbo"
' 	}
' 

set oauth2 = Server.CreateObject("Chilkat.OAuth2")

oauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token"

' Replace these with actual values.
oauth2.ClientId = "GOOGLE-CLIENT-ID"
oauth2.ClientSecret = "GOOGLE-CLIENT-SECRET"

' Get the "refresh_token"
oauth2.RefreshToken = jsonToken.StringOf("refresh_token")

' Send the HTTP POST to refresh the access token..
success = oauth2.RefreshAccessToken()
If (success <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( oauth2.LastErrorText) & "</pre>"
    Response.End
End If

' The response contains a new access token, but we must keep
' our existing refresh token for when we need to refresh again in the future.
success = jsonToken.UpdateString("access_token",oauth2.AccessToken)

' Save the new JSON access token response to a file.
set sbJson = Server.CreateObject("Chilkat.StringBuilder")
jsonToken.EmitCompact = 0
success = jsonToken.EmitSb(sbJson)
success = sbJson.WriteFile("qa_data/tokens/_gmailSmtp.json","utf-8",0)

Response.Write "<pre>" & Server.HTMLEncode( "OAuth2 authorization granted!") & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( "New Access Token = " & oauth2.AccessToken) & "</pre>"

%>
</body>
</html>