Xojo Plugin

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.) Xojo Plugin

Dim success As Boolean
success = 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 New Chilkat.StringBuilder
success = sbToken.LoadFile("qa_data/tokens/googleCloudStorageAccessToken.txt","utf-8")
If (success = False) Then
    System.DebugLog("Failed to load access token.")
    Return
End If

Dim http As New Chilkat.Http

http.AuthToken = sbToken.GetAsString()

// Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
success = http.SetUrlVar("bucket_name","chilkat-ocean")
success = http.SetUrlVar("object_name","starfish.jpg")
Dim url As String
url = "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 New Chilkat.BinData
success = http.DownloadBd(url,fileData)
Dim responseCode As Int32
responseCode = http.LastStatus
If ((success = False) And (responseCode <> 401)) Then
    System.DebugLog(http.LastErrorText)
    Return
End If

If (responseCode = 401) Then
    System.DebugLog("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 New Chilkat.FileAccess
    Dim jsonKey As String
    jsonKey = fac.ReadEntireTextFile("qa_data/googleApi/ChilkatCloud-13a07a2e8b3f.json","utf-8")
    If (fac.LastMethodSuccess <> True) Then
        System.DebugLog(fac.LastErrorText)
        Return
    End If

    Dim gAuth As New Chilkat.AuthGoogle
    gAuth.JsonKey = jsonKey
    gAuth.Scope = "https://www.googleapis.com/auth/cloud-platform"
    gAuth.ExpireNumSeconds = 3600
    gAuth.SubEmailAddress = ""

    Dim tlsSock As New Chilkat.Socket
    success = tlsSock.Connect("www.googleapis.com",443,True,5000)
    If (success <> True) Then
        System.DebugLog(tlsSock.LastErrorText)
        Return
    End If

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

    success = 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
        System.DebugLog(http.LastErrorText)
        Return
    End If

End If

If (responseCode <> 200) Then
    // Get the error response
    Dim sbErrorResponse As New Chilkat.StringBuilder
    success = sbErrorResponse.AppendBd(fileData,"utf-8",0,0)
    System.DebugLog("Error response code = " + Str(responseCode))
    System.DebugLog("Error:")
    System.DebugLog(sbErrorResponse.GetAsString())
    Return
End If

System.DebugLog("Success.")

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