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

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

' 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..
set sbToken = Server.CreateObject("Chilkat.StringBuilder")
success = sbToken.LoadFile("qa_data/tokens/googleCloudStorageAccessToken.txt","utf-8")
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( "Failed to load access token.") & "</pre>"
    Response.End
End If

set http = Server.CreateObject("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")
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..
set fileData = Server.CreateObject("Chilkat.BinData")
success = http.DownloadBd(url,fileData)
responseCode = http.LastStatus
If ((success = 0) And (responseCode <> 401)) Then
    Response.Write "<pre>" & Server.HTMLEncode( http.LastErrorText) & "</pre>"
    Response.End
End If

If (responseCode = 401) Then
    Response.Write "<pre>" & Server.HTMLEncode( "Received 401 Unauthorized response. Attempting to refresh the access token...") & "</pre>"

    ' May be that the access token expired.
    ' Load our JSON key and request a new access token, then retry the original request.
    set fac = Server.CreateObject("Chilkat.FileAccess")
    jsonKey = fac.ReadEntireTextFile("qa_data/googleApi/ChilkatCloud-13a07a2e8b3f.json","utf-8")
    If (fac.LastMethodSuccess <> 1) Then
        Response.Write "<pre>" & Server.HTMLEncode( fac.LastErrorText) & "</pre>"
        Response.End
    End If

    set gAuth = Server.CreateObject("Chilkat.AuthGoogle")
    gAuth.JsonKey = jsonKey
    gAuth.Scope = "https://www.googleapis.com/auth/cloud-platform"
    gAuth.ExpireNumSeconds = 3600
    gAuth.SubEmailAddress = ""

    set tlsSock = Server.CreateObject("Chilkat.Socket")
    success = tlsSock.Connect("www.googleapis.com",443,1,5000)
    If (success <> 1) Then
        Response.Write "<pre>" & Server.HTMLEncode( tlsSock.LastErrorText) & "</pre>"
        Response.End
    End If

    success = gAuth.ObtainAccessToken(tlsSock)
    If (success <> 1) Then
        Response.Write "<pre>" & Server.HTMLEncode( gAuth.LastErrorText) & "</pre>"
        Response.End
    End If

    success = fac.WriteEntireTextFile("qa_data/tokens/googleCloudStorageAccessToken.txt",gAuth.AccessToken,"utf-8",0)

    ' Retry the original request.
    http.AuthToken = gAuth.AccessToken
    success = http.DownloadBd(url,fileData)
    If (success = 0) Then
        Response.Write "<pre>" & Server.HTMLEncode( http.LastErrorText) & "</pre>"
        Response.End
    End If

End If

If (responseCode <> 200) Then
    ' Get the error response
    set sbErrorResponse = Server.CreateObject("Chilkat.StringBuilder")
    success = sbErrorResponse.AppendBd(fileData,"utf-8",0,0)
    Response.Write "<pre>" & Server.HTMLEncode( "Error response code = " & responseCode) & "</pre>"
    Response.Write "<pre>" & Server.HTMLEncode( "Error:") & "</pre>"
    Response.Write "<pre>" & Server.HTMLEncode( sbErrorResponse.GetAsString()) & "</pre>"
    Response.End
End If

Response.Write "<pre>" & Server.HTMLEncode( "Success.") & "</pre>"

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

%>
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</html>