(Tcl) 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.)

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load ./chilkat.dll

# 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 [new_CkStringBuilder]

set success [CkStringBuilder_LoadFile $sbToken "qa_data/tokens/googleCloudStorageAccessToken.txt" "utf-8"]
if {$success == 0} then {
    puts "Failed to load access token."
    delete_CkStringBuilder $sbToken
    exit
}

set http [new_CkHttp]

CkHttp_put_AuthToken $http [CkStringBuilder_getAsString $sbToken]

# Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
CkHttp_SetUrlVar $http "bucket_name" "chilkat-ocean"
CkHttp_SetUrlVar $http "object_name" "starfish.jpg"
set url "https://www.googleapis.com/storage/v1/b/{$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 [new_CkBinData]

set success [CkHttp_DownloadBd $http $url $fileData]
set responseCode [CkHttp_get_LastStatus $http]
if {expr [$success == 0]  &&  [$responseCode != 401]} then {
    puts [CkHttp_lastErrorText $http]
    delete_CkStringBuilder $sbToken
    delete_CkHttp $http
    delete_CkBinData $fileData
    exit
}

if {$responseCode == 401} then {
    puts "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.
    set fac [new_CkFileAccess]

    set jsonKey [CkFileAccess_readEntireTextFile $fac "qa_data/googleApi/ChilkatCloud-13a07a2e8b3f.json" "utf-8"]
    if {[CkFileAccess_get_LastMethodSuccess $fac] != 1} then {
        puts [CkFileAccess_lastErrorText $fac]
        delete_CkStringBuilder $sbToken
        delete_CkHttp $http
        delete_CkBinData $fileData
        delete_CkFileAccess $fac
        exit
    }

    set gAuth [new_CkAuthGoogle]

    CkAuthGoogle_put_JsonKey $gAuth $jsonKey
    CkAuthGoogle_put_Scope $gAuth "https://www.googleapis.com/auth/cloud-platform"
    CkAuthGoogle_put_ExpireNumSeconds $gAuth 3600
    CkAuthGoogle_put_SubEmailAddress $gAuth ""

    set tlsSock [new_CkSocket]

    set success [CkSocket_Connect $tlsSock "www.googleapis.com" 443 1 5000]
    if {$success != 1} then {
        puts [CkSocket_lastErrorText $tlsSock]
        delete_CkStringBuilder $sbToken
        delete_CkHttp $http
        delete_CkBinData $fileData
        delete_CkFileAccess $fac
        delete_CkAuthGoogle $gAuth
        delete_CkSocket $tlsSock
        exit
    }

    set success [CkAuthGoogle_ObtainAccessToken $gAuth $tlsSock]
    if {$success != 1} then {
        puts [CkAuthGoogle_lastErrorText $gAuth]
        delete_CkStringBuilder $sbToken
        delete_CkHttp $http
        delete_CkBinData $fileData
        delete_CkFileAccess $fac
        delete_CkAuthGoogle $gAuth
        delete_CkSocket $tlsSock
        exit
    }

    CkFileAccess_WriteEntireTextFile $fac "qa_data/tokens/googleCloudStorageAccessToken.txt" [CkAuthGoogle_accessToken $gAuth] "utf-8" 0

    # Retry the original request.
    CkHttp_put_AuthToken $http [CkAuthGoogle_accessToken $gAuth]
    set success [CkHttp_DownloadBd $http $url $fileData]
    if {$success == 0} then {
        puts [CkHttp_lastErrorText $http]
        delete_CkStringBuilder $sbToken
        delete_CkHttp $http
        delete_CkBinData $fileData
        delete_CkFileAccess $fac
        delete_CkAuthGoogle $gAuth
        delete_CkSocket $tlsSock
        exit
    }

}

if {$responseCode != 200} then {
    # Get the error response
    set sbErrorResponse [new_CkStringBuilder]

    CkStringBuilder_AppendBd $sbErrorResponse $fileData "utf-8" 0 0
    puts "Error response code = $responseCode"
    puts "Error:"
    puts [CkStringBuilder_getAsString $sbErrorResponse]
    delete_CkStringBuilder $sbToken
    delete_CkHttp $http
    delete_CkBinData $fileData
    delete_CkFileAccess $fac
    delete_CkAuthGoogle $gAuth
    delete_CkSocket $tlsSock
    delete_CkStringBuilder $sbErrorResponse
    exit
}

puts "Success."

# Save the downloaded data to a file.
set success [CkBinData_WriteFile $fileData "qa_output/starfish.jpg"]

delete_CkStringBuilder $sbToken
delete_CkHttp $http
delete_CkBinData $fileData
delete_CkFileAccess $fac
delete_CkAuthGoogle $gAuth
delete_CkSocket $tlsSock
delete_CkStringBuilder $sbErrorResponse