(DataFlex) Get XOAUTH2 Access Token from Google OAuth 2.0 Authorization Server

Obtains an OAUTH2 access token from the Google OAuth 2.0 Authorization Server. This is for Server to server applications using Google API's that need an access token. See https://developers.google.com/accounts/docs/OAuth2ServiceAccount

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

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoHttp
    Variant vCert
    Handle hoCert
    Boolean iSuccess
    String sIss
    String sScope
    String sS_sub
    Integer iNumSec
    String sAccessToken
    String sTemp1
    Boolean bTemp1

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

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

    // When a service account (Client ID) is created at https://code.google.com/apis/console/
    // Google will generate a P12 key.  This is a PKCS12 (PFX) file that you will download
    // and save.  The password to access the contents of this file is "notasecret".
    // NOTE: The Chilkat Pfx API provides the ability to load a PFX/P12 and re-save
    // with a different password.

    // Begin by loading the downloaded .p12 into a Chilkat certificate object:
    Get Create (RefClass(cComChilkatCert)) To hoCert
    If (Not(IsComObjectCreated(hoCert))) Begin
        Send CreateComObject of hoCert
    End
    Get ComLoadPfxFile Of hoCert "/myDir/API Project-1c43a291e2a1-notasecret.p12" "notasecret" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoCert To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // The next (and final) step is to request the access token.  Chilkat internally
    // does all the work of forming the JWT header and JWT claim set, encoding and
    // signing the JWT, and sending the access token request.
    // The application need only provide the inputs: The iss, scope(s), sub, and the
    // desired duration with a max of 3600 seconds (1 hour).
    // 
    // Each of these inputs is defined as follows 
    // (see https://developers.google.com/accounts/docs/OAuth2ServiceAccount
    // 
    // iss: The email address of the service account.
    // 
    // scope: A space-delimited list of the permissions that the application requests.
    // 
    // sub: required if there is an email address, such as for a
    //   Google Apps domain—if you use Google Apps for Work, where the administrator of the Google Apps domain 
    //   can authorize an application to access user data on behalf of users in the Google Apps domain.
    // 
    // numSec: The number of seconds for which the access token will be valid (max 3600).

    Move "761326798069-r5mljlln1rd4lrbhg75efgigp36m78j5@developer.gserviceaccount.com" To sIss
    Move "https://mail.google.com/" To sScope
    // Leave "sub" empty if there is no Google Apps email.
    Move "" To sS_sub
    Move 3600 To iNumSec

    Get pvComObject of hoCert to vCert
    Get ComG_SvcOauthAccessToken Of hoHttp sIss sScope sS_sub iNumSec vCert To sAccessToken
    Get ComLastMethodSuccess Of hoHttp To bTemp1
    If (bTemp1 <> True) Begin
        Get ComLastErrorText Of hoHttp To sTemp1
        Showln sTemp1
    End
    Else Begin
        Showln "access token: " sAccessToken
    End



End_Procedure