(Excel) Refresh a Constant Contact OAuth2 Access Token

Refreshes a Constant Contact OAuth2 access token. When an access token expires, HTTPS requests will receive a 401 status response indicating failure. When that happens, your application can run this code to refresh the access token, and then retry the request using the new access token. Refreshing an access token does not need user interaction (i.e. does not need to display a browser to have the user interactive authorize access).

For more information, see https://v3.developer.constantcontact.com/api_guide/server_flow.html#step-5-refresh-the-access-token

Download Excel Class Modules Chilkat Excel Class Modules

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

' It is assumed we previously obtained an OAuth2 access token.
' This example loads the JSON access token file 
' saved by this example: Get Constant Contact OAuth2 Access Token

Dim jsonToken As Chilkat.JsonObject
Set jsonToken = Chilkat.NewJsonObject

success = jsonToken.LoadFile("qa_data/tokens/constantContact.json")
If (success <> True) Then
    Debug.Print "Failed to load constantContact.json"
    Exit Sub
End If

' The access token JSON looks like this:

' {
'   "access_token": "aEr4czHReESHUGcc2LRknzsMxUbW",
'   "refresh_token": "s2qH27ikM7r3Ia0LrZGDOIgKw0bubUotBdJ7fTtc7y",
'   "token_type": "Bearer"
' }

Dim oauth2 As Chilkat.OAuth2
Set oauth2 = Chilkat.NewOAuth2

oauth2.VerboseLogging = True

oauth2.TokenEndpoint = "https://idfed.constantcontact.com/as/token.oauth2"
oauth2.UseBasicAuth = True
oauth2.UncommonOptions = "OAUTH2_REFRESH_NO_SCOPE"

' Replace these with actual values.
oauth2.ClientId = "CLIENT_KEY"
oauth2.ClientSecret = "CLIENT_SECRET"

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

Debug.Print "Existing refresh_token: "; oauth2.RefreshToken

' Send the HTTP POST to refresh the access token..
success = oauth2.RefreshAccessToken()
If (success <> True) Then
    Debug.Print oauth2.LastErrorText
    Exit Sub
End If

Dim success As Boolean
success = jsonToken.UpdateString("access_token",oauth2.AccessToken)
success = jsonToken.UpdateString("refresh_token",oauth2.RefreshToken)

' Save the new JSON access token response to a file.
Dim sbJson As Chilkat.StringBuilder
Set sbJson = Chilkat.NewStringBuilder
jsonToken.EmitCompact = False
success = jsonToken.EmitSb(sbJson)
success = sbJson.WriteFile("qa_data/tokens/constantContact.json","utf-8",False)

Debug.Print "OAuth2 token refreshed!"
Debug.Print "New Access Token = "; oauth2.AccessToken
Debug.Print "New refresh_token: "; oauth2.RefreshToken