(DataFlex) 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.)

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-9.5.0-win32.pkg

Procedure Test
    Handle hoSbToken
    Boolean iSuccess
    Handle hoHttp
    String sUrl
    Variant vFileData
    Handle hoFileData
    Integer iResponseCode
    Handle hoFac
    String sJsonKey
    Handle hoGAuth
    Variant vTlsSock
    Handle hoTlsSock
    Handle hoSbErrorResponse
    String sTemp1
    Boolean bTemp1

    // 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..
    Get Create (RefClass(cComChilkatStringBuilder)) To hoSbToken
    If (Not(IsComObjectCreated(hoSbToken))) Begin
        Send CreateComObject of hoSbToken
    End
    Get ComLoadFile Of hoSbToken "qa_data/tokens/googleCloudStorageAccessToken.txt" "utf-8" To iSuccess
    If (iSuccess = False) Begin
        Showln "Failed to load access token."
        Procedure_Return
    End

    Get Create (RefClass(cComChilkatHttp)) To hoHttp
    If (Not(IsComObjectCreated(hoHttp))) Begin
        Send CreateComObject of hoHttp
    End

    Get ComGetAsString Of hoSbToken To sTemp1
    Set ComAuthToken Of hoHttp To sTemp1

    // Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
    Get ComSetUrlVar Of hoHttp "bucket_name" "chilkat-ocean" To iSuccess
    Get ComSetUrlVar Of hoHttp "object_name" "starfish.jpg" To iSuccess
    Move "https://www.googleapis.com/storage/v1/b/{$bucket_name}/o/{$object_name}?alt=media" To sUrl

    // If there is an error response, then we didn't actually download the file data,
    // but instead we downloaded an error response..
    Get Create (RefClass(cComChilkatBinData)) To hoFileData
    If (Not(IsComObjectCreated(hoFileData))) Begin
        Send CreateComObject of hoFileData
    End
    Get pvComObject of hoFileData to vFileData
    Get ComDownloadBd Of hoHttp sUrl vFileData To iSuccess
    Get ComLastStatus Of hoHttp To iResponseCode
    If ((iSuccess = False) And (iResponseCode <> 401)) Begin
        Get ComLastErrorText Of hoHttp To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    If (iResponseCode = 401) Begin
        Showln "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.
        Get Create (RefClass(cComCkFileAccess)) To hoFac
        If (Not(IsComObjectCreated(hoFac))) Begin
            Send CreateComObject of hoFac
        End
        Get ComReadEntireTextFile Of hoFac "qa_data/googleApi/ChilkatCloud-13a07a2e8b3f.json" "utf-8" To sJsonKey
        Get ComLastMethodSuccess Of hoFac To bTemp1
        If (bTemp1 <> True) Begin
            Get ComLastErrorText Of hoFac To sTemp1
            Showln sTemp1
            Procedure_Return
        End

        Get Create (RefClass(cComChilkatAuthGoogle)) To hoGAuth
        If (Not(IsComObjectCreated(hoGAuth))) Begin
            Send CreateComObject of hoGAuth
        End
        Set ComJsonKey Of hoGAuth To sJsonKey
        Set ComScope Of hoGAuth To "https://www.googleapis.com/auth/cloud-platform"
        Set ComExpireNumSeconds Of hoGAuth To 3600
        Set ComSubEmailAddress Of hoGAuth To ""

        Get Create (RefClass(cComChilkatSocket)) To hoTlsSock
        If (Not(IsComObjectCreated(hoTlsSock))) Begin
            Send CreateComObject of hoTlsSock
        End
        Get ComConnect Of hoTlsSock "www.googleapis.com" 443 True 5000 To iSuccess
        If (iSuccess <> True) Begin
            Get ComLastErrorText Of hoTlsSock To sTemp1
            Showln sTemp1
            Procedure_Return
        End

        Get pvComObject of hoTlsSock to vTlsSock
        Get ComObtainAccessToken Of hoGAuth vTlsSock To iSuccess
        If (iSuccess <> True) Begin
            Get ComLastErrorText Of hoGAuth To sTemp1
            Showln sTemp1
            Procedure_Return
        End

        Get ComAccessToken Of hoGAuth To sTemp1
        Get ComWriteEntireTextFile Of hoFac "qa_data/tokens/googleCloudStorageAccessToken.txt" sTemp1 "utf-8" False To iSuccess

        // Retry the original request.
        Get ComAccessToken Of hoGAuth To sTemp1
        Set ComAuthToken Of hoHttp To sTemp1
        Get pvComObject of hoFileData to vFileData
        Get ComDownloadBd Of hoHttp sUrl vFileData To iSuccess
        If (iSuccess = False) Begin
            Get ComLastErrorText Of hoHttp To sTemp1
            Showln sTemp1
            Procedure_Return
        End

    End

    If (iResponseCode <> 200) Begin
        // Get the error response
        Get Create (RefClass(cComChilkatStringBuilder)) To hoSbErrorResponse
        If (Not(IsComObjectCreated(hoSbErrorResponse))) Begin
            Send CreateComObject of hoSbErrorResponse
        End
        Get pvComObject of hoFileData to vFileData
        Get ComAppendBd Of hoSbErrorResponse vFileData "utf-8" 0 0 To iSuccess
        Showln "Error response code = " iResponseCode
        Showln "Error:"
        Get ComGetAsString Of hoSbErrorResponse To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "Success."

    // Save the downloaded data to a file.
    Get ComWriteFile Of hoFileData "qa_output/starfish.jpg" To iSuccess


End_Procedure