(DataFlex) Automatically Refresh Token for 401 Unauthorized

Demonstrates how to automatically refresh an access token (without user interaction) when the token expires and a 401 Unauthorized response is received.

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

Use ChilkatAx-win32.pkg

Procedure Test
    String sTokenFilePath
    Handle hoJsonToken
    Boolean iSuccess
    Handle hoHttp
    String sJsonResponse
    Handle hoOauth2
    Variant vSbJson
    Handle hoSbJson
    String sTemp1
    Integer iTemp1
    Boolean bTemp1

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

    Move "qa_data/tokens/googleCalendar.json" To sTokenFilePath

    // Get our current access token.
    Get Create (RefClass(cComChilkatJsonObject)) To hoJsonToken
    If (Not(IsComObjectCreated(hoJsonToken))) Begin
        Send CreateComObject of hoJsonToken
    End
    Get ComLoadFile Of hoJsonToken sTokenFilePath To iSuccess
    Get ComHasMember Of hoJsonToken "access_token" To bTemp1
    If (bTemp1 = False) Begin
        Showln "No access token found."
        Procedure_Return
    End

    Get Create (RefClass(cComChilkatHttp)) To hoHttp
    If (Not(IsComObjectCreated(hoHttp))) Begin
        Send CreateComObject of hoHttp
    End
    Get ComStringOf Of hoJsonToken "access_token" To sTemp1
    Set ComAuthToken Of hoHttp To sTemp1

    Get ComQuickGetStr Of hoHttp "https://www.googleapis.com/calendar/v3/users/me/calendarList" To sJsonResponse
    Get ComLastMethodSuccess Of hoHttp To bTemp1
    If (bTemp1 <> True) Begin

        Get ComLastStatus Of hoHttp To iTemp1
        If (iTemp1 <> 401) Begin
            Get ComLastErrorText Of hoHttp To sTemp1
            Showln sTemp1
            Showln "----"
            Get ComLastResponseBody Of hoHttp To sTemp1
            Showln sTemp1
            Procedure_Return
        End

        // The access token must've expired. 
        // Refresh the access token and then retry the request.
        Get Create (RefClass(cComChilkatOAuth2)) To hoOauth2
        If (Not(IsComObjectCreated(hoOauth2))) Begin
            Send CreateComObject of hoOauth2
        End

        Set ComTokenEndpoint Of hoOauth2 To "https://www.googleapis.com/oauth2/v4/token"

        // Replace these with actual values.
        Set ComClientId Of hoOauth2 To "GOOGLE-CLIENT-ID"
        Set ComClientSecret Of hoOauth2 To "GOOGLE-CLIENT-SECRET"

        // Get the "refresh_token"
        Get ComStringOf Of hoJsonToken "refresh_token" To sTemp1
        Set ComRefreshToken Of hoOauth2 To sTemp1

        // Send the HTTP POST to refresh the access token..
        Get ComRefreshAccessToken Of hoOauth2 To iSuccess
        If (iSuccess <> True) Begin
            Get ComLastErrorText Of hoOauth2 To sTemp1
            Showln sTemp1
            Procedure_Return
        End

        // The response contains a new access token, but we must keep
        // our existing refresh token for when we need to refresh again in the future.
        Get ComAccessToken Of hoOauth2 To sTemp1
        Get ComUpdateString Of hoJsonToken "access_token" sTemp1 To iSuccess

        // Save the new JSON access token response to a file.
        Get Create (RefClass(cComChilkatStringBuilder)) To hoSbJson
        If (Not(IsComObjectCreated(hoSbJson))) Begin
            Send CreateComObject of hoSbJson
        End
        Set ComEmitCompact Of hoJsonToken To False
        Get pvComObject of hoSbJson to vSbJson
        Get ComEmitSb Of hoJsonToken vSbJson To iSuccess
        Get ComWriteFile Of hoSbJson sTokenFilePath "utf-8" False To iSuccess

        Showln "OAuth2 authorization granted!"
        Get ComAccessToken Of hoOauth2 To sTemp1
        Showln "New Access Token = " sTemp1

        // re-try the original request.
        Get ComAccessToken Of hoOauth2 To sTemp1
        Set ComAuthToken Of hoHttp To sTemp1
        Get ComQuickGetStr Of hoHttp "https://www.googleapis.com/calendar/v3/users/me/calendarList" To sJsonResponse
        Get ComLastMethodSuccess Of hoHttp To bTemp1
        If (bTemp1 <> True) Begin
            Get ComLastErrorText Of hoHttp To sTemp1
            Showln sTemp1
            Procedure_Return
        End

    End

    Showln sJsonResponse
    Showln "-----------------------------"


End_Procedure