Visual FoxPro

Refresh Expiring OAuth2 Access Token for Azure Registered App

See more OAuth2 Examples

Shows how to renew an Azure App's access token using the refresh token when it's near expiration. Visual FoxPro

LOCAL lnSuccess
LOCAL loJson
LOCAL loDtExpire
LOCAL loOauth2
LOCAL loFac

lnSuccess = 0

* We previously obtained an access token and saved the JSON to a file using this example:
* Get OAuth2 Access Token for Azure Registered App

* This example will examine the JSON and expiration date, and if near expiration will
* refresh the access token.

loJson = CreateObject('Chilkat.JsonObject')
lnSuccess = loJson.LoadFile("qa_data/tokens/_myAzureApp.json")
IF (lnSuccess <> 1) THEN
    ? "Failed to load the access token."
    RELEASE loJson
    CANCEL
ENDIF

* The contents of the JSON look like this:
* {
*   "token_type": "Bearer",
*   "scope": "User.Read Mail.ReadWrite Mail.Send",
*   "expires_in": 3600,
*   "ext_expires_in": 0,
*   "access_token": "EwBAA8l6B...",
*   "refresh_token": "MCRMdbe6Cd...",
*   "id_token": "eyJ0eXAiOiJ...",
*   "expires_on": "1494112119"
* }

* The "expires_on" value is a Unix time.
loDtExpire = CreateObject('Chilkat.CkDateTime')
loDtExpire.SetFromUnixTime(0,loJson.IntOf("expires_on"))

* If this date/time expires within 10 minutes of the current system time, refresh the token.
IF (loDtExpire.ExpiresWithin(10,"minutes") <> 1) THEN
    ? "No need to refresh, the access token won't expire within the next 10 minutes."
    RELEASE loJson
    RELEASE loDtExpire
    CANCEL
ENDIF

* OK, we need to refresh the access token..
loOauth2 = CreateObject('Chilkat.OAuth2')

* Note: The endpoint depends on the Azure App Registration.
* See How to Choose the Correct Endpoints for your Azure App Registration
loOauth2.TokenEndpoint = "https://login.microsoftonline.com/common/oauth2/v2.0/token"

* Use your client ID.
loOauth2.ClientId = "CLIENT_ID"

* Get the existing refresh token.
loOauth2.RefreshToken = loJson.StringOf("refresh_token")

* Send the HTTP POST to refresh the access token.
lnSuccess = loOauth2.RefreshAccessToken()
IF (lnSuccess = 0) THEN
    ? loOauth2.LastErrorText
    RELEASE loJson
    RELEASE loDtExpire
    RELEASE loOauth2
    CANCEL
ENDIF

? "OAuth2 authorization granted!"
? "Access Token = " + loOauth2.AccessToken

* Get the full JSON response:
loJson.Load(loOauth2.AccessTokenResponse)
loJson.EmitCompact = 0

* If an "expires_on" member does not exist, then add the JSON member by
* getting the current system date/time and adding the "expires_in" seconds.
* This way we'll know when the token expires.
IF (loJson.HasMember("expires_on") <> 1) THEN
    loDtExpire.SetFromCurrentSystemTime()
    loDtExpire.AddSeconds(loJson.IntOf("expires_in"))
    loJson.AppendString("expires_on",loDtExpire.GetAsUnixTimeStr(0))
ENDIF

? loJson.Emit()

* Save the new access token JSON to a file for future requests.
loFac = CreateObject('Chilkat.FileAccess')
loFac.WriteEntireTextFile("qa_data/tokens/_myAzureApp.json",loJson.Emit(),"utf-8",0)

RELEASE loJson
RELEASE loDtExpire
RELEASE loOauth2
RELEASE loFac