B4X

Refresh Access Token on 401 Unauthorized and Retry (Service Account)

See more Google Cloud Storage Examples

Demonstrates how to handle an expired access token error, refresh the token, and retry the request. (In this case, the request is to download an object from Google Cloud Storage.) B4X

Dim success As Boolean = False

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

'  This example uses a previously obtained access token having permission for the 
'  scope "https://www.googleapis.com/auth/cloud-platform"

'  In this example, Get Google Cloud Storage OAuth2 Access Token, 
'  the service account access token was saved to a text file.  This example fetches the access token from the file..
Dim sbToken As ChilkatStringBuilder
sbToken.Initialize
success = sbToken.LoadFile("qa_data/tokens/googleCloudStorageAccessToken.txt", "utf-8")
If success = False Then
    Log("Failed to load access token.")
    Return
End If


Dim http As ChilkatHttp
http.Initialize("http")

http.AuthToken = sbToken.GetAsString

'  Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
http.SetUrlVar("bucket_name", "chilkat-ocean")
http.SetUrlVar("object_name", "starfish.jpg")
Dim url As String = "https://www.googleapis.com/storage/v1/b/{$bucket_name}/o/{$object_name}?alt=media"

'  If there is an error response, then we didn't actually download the file data,
'  but instead we downloaded an error response..
Dim fileData As ChilkatBinData
fileData.Initialize
success = http.DownloadBd(url, fileData)
Dim responseCode As Int = http.LastStatus
If (success = False) And (responseCode <> 401) Then
    Log(http.LastErrorText)
    Return
End If


If responseCode = 401 Then
    Log("Received 401 Unauthorized response. Attempting to refresh the access token...")

    '  May be that the access token expired.
    '  Load our JSON key and request a new access token, then retry the original request.
    Dim fac As ChilkatFileAccess
    fac.Initialize
    Dim jsonKey As String = fac.ReadEntireTextFile("qa_data/googleApi/ChilkatCloud-13a07a2e8b3f.json", "utf-8")
    If fac.LastMethodSuccess <> True Then
        Log(fac.LastErrorText)
        Return
    End If


    Dim gAuth As ChilkatAuthGoogle
    gAuth.Initialize("gAuth")
    gAuth.JsonKey = jsonKey
    gAuth.Scope = "https://www.googleapis.com/auth/cloud-platform"
    gAuth.ExpireNumSeconds = 3600
    gAuth.SubEmailAddress = ""

    Dim tlsSock As ChilkatSocket
    tlsSock.Initialize("tlsSock")
    success = tlsSock.Connect("www.googleapis.com", 443, True, 5000)
    If success <> True Then
        Log(tlsSock.LastErrorText)
        Return
    End If


    success = gAuth.ObtainAccessToken(tlsSock)
    If success <> True Then
        Log(gAuth.LastErrorText)
        Return
    End If


    fac.WriteEntireTextFile("qa_data/tokens/googleCloudStorageAccessToken.txt", gAuth.AccessToken, "utf-8", False)

    '  Retry the original request.
    http.AuthToken = gAuth.AccessToken
    success = http.DownloadBd(url, fileData)
    If success = False Then
        Log(http.LastErrorText)
        Return
    End If


End If


If responseCode <> 200 Then
    '  Get the error response
    Dim sbErrorResponse As ChilkatStringBuilder
    sbErrorResponse.Initialize
    sbErrorResponse.AppendBd(fileData, "utf-8", 0, 0)
    Log("Error response code = " & responseCode)
    Log("Error:")
    Log(sbErrorResponse.GetAsString)
    Return
End If


Log("Success.")

'  Save the downloaded data to a file.
success = fileData.WriteFile("qa_output/starfish.jpg")