(SQL Server) 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

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    -- This example assumes the Chilkat API to have been previously unlocked.
    -- See Global Unlock Sample for sample code.

    DECLARE @http int
    -- Use "Chilkat_9_5_0.Http" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Http', @http OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    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:
    DECLARE @cert int
    -- Use "Chilkat_9_5_0.Cert" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Cert', @cert OUT

    DECLARE @success int
    EXEC sp_OAMethod @cert, 'LoadPfxFile', @success OUT, '/myDir/API Project-1c43a291e2a1-notasecret.p12', 'notasecret'
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @cert, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @http
        EXEC @hr = sp_OADestroy @cert
        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).

    DECLARE @iss nvarchar(4000)
    SELECT @iss = '761326798069-r5mljlln1rd4lrbhg75efgigp36m78j5@developer.gserviceaccount.com'
    DECLARE @scope nvarchar(4000)
    SELECT @scope = 'https://mail.google.com/'
    -- Leave "sub" empty if there is no Google Apps email.
    DECLARE @s_sub nvarchar(4000)
    SELECT @s_sub = ''
    DECLARE @numSec int
    SELECT @numSec = 3600

    DECLARE @accessToken nvarchar(4000)
    EXEC sp_OAMethod @http, 'G_SvcOauthAccessToken', @accessToken OUT, @iss, @scope, @s_sub, @numSec, @cert
    EXEC sp_OAGetProperty @http, 'LastMethodSuccess', @iTmp0 OUT
    IF @iTmp0 <> 1
      BEGIN
        EXEC sp_OAGetProperty @http, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
      END
    ELSE
      BEGIN

        PRINT 'access token: ' + @accessToken
      END

    EXEC @hr = sp_OADestroy @http
    EXEC @hr = sp_OADestroy @cert


END
GO