Xbase++

Get Google API Access Token using JSON Private Key

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Demonstrates how to get a Google API access token using a JSON service account private key. Xbase++

LOCAL nSuccess
LOCAL oFac
LOCAL cJsonKey
LOCAL oGAuth
LOCAL oTlsSock
LOCAL cAccessToken
LOCAL oMailman
LOCAL oEmail

nSuccess := 0

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

//  --------------------------------------------------------------------------------
//  For a step-by-step guide for setting up your Google Workspace service account,
//  see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
//  --------------------------------------------------------------------------------

//  First load the JSON key into a string.
oFac := CreateObject("Chilkat.FileAccess")
cJsonKey := oFac:ReadEntireTextFile("qa_data/googleApi/chilkat25-b4214220e565.json", "utf-8")
IF (oFac:LastMethodSuccess != 1)
    ? oFac:LastErrorText
    oFac:destroy()
    RETURN
ENDIF

//  A Google service account JSON private key looks like this:

//  {
//    "type": "service_account",
//    "project_id": "chilkat25",
//    "private_key_id": "b4214220f565881e19eeb97c2699bf5a0d1e3e0b",
//    "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvQ...NXcM=\n-----END PRIVATE KEY-----\n",
//    "client_email": "chilkatsvc@chilkat25.iam.gserviceaccount.com",
//    "client_id": "109122032928932715958",
//    "auth_uri": "https://accounts.google.com/o/oauth2/auth",
//    "token_uri": "https://oauth2.googleapis.com/token",
//    "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
//    "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/chilkatsvc%40chilkat25.iam.gserviceaccount.com",
//    "universe_domain": "googleapis.com"
//  }

oGAuth := CreateObject("Chilkat.AuthGoogle")
oGAuth:JsonKey := cJsonKey

//  Specify a scope.
oGAuth:Scope := "https://mail.google.com/"

//  Request an access token that is valid for this many seconds.
oGAuth:ExpireNumSeconds := 3600

//  When using a Google Workspace account with Gmail APIs, a service account can impersonate a user 
//  via a process called domain-wide delegation — and the "sub" claim in the JWT is what enables this.
//  Domain-wide delegation allows a Google Workspace administrator to authorize a service account to 
//  act on behalf of any user in the domain, without user interaction.

//  This is required for server-to-server access to user data — such as reading/sending Gmail from a background service.
//  This is your company email address.
oGAuth:SubEmailAddress := "info@chilkat.xyz"

//  Connect to www.googleapis.com using TLS
oTlsSock := CreateObject("Chilkat.Socket")
nSuccess := oTlsSock:Connect("www.googleapis.com", 443, 1, 5000)
IF (nSuccess != 1)
    ? oTlsSock:LastErrorText
    oFac:destroy()
    oGAuth:destroy()
    oTlsSock:destroy()
    RETURN
ENDIF

//  Send the request to obtain the access token.
nSuccess := oGAuth:ObtainAccessToken(oTlsSock)
IF (nSuccess != 1)
    ? oGAuth:LastErrorText
    oFac:destroy()
    oGAuth:destroy()
    oTlsSock:destroy()
    RETURN
ENDIF

//  Examine the access token:
cAccessToken := oGAuth:AccessToken
? "Access Token: " + cAccessToken

//  Sample output:
//  ya29.a0AW4XtxjGTD67Z8 .... IRw0218

//  The access token allows us to send unlimited emails while it's valid. Once it expires, we must obtain and use a new one.

//  -----------------------------------------------------------------------
oMailman := CreateObject("Chilkat.MailMan")

//  Set the properties for the GMail SMTP server:
oMailman:SmtpHost := "smtp.gmail.com"
oMailman:SmtpPort := 587
oMailman:StartTLS := 1

oMailman:SmtpUsername := "info@chilkat.xyz"
oMailman:OAuth2AccessToken := cAccessToken

//  Create a new email object
oEmail := CreateObject("Chilkat.Email")

oEmail:Subject := "This is a test"
oEmail:Body := "This is a test"
oEmail:From := "Chilkat Test <info@chilkat.xyz>"
nSuccess := oEmail:AddTo("Chilkat Software", "info@chilkatsoft.com")
//  To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

nSuccess := oMailman:SendEmail(oEmail)
IF (nSuccess != 1)
    ? oMailman:LastErrorText
    oFac:destroy()
    oGAuth:destroy()
    oTlsSock:destroy()
    oMailman:destroy()
    oEmail:destroy()
    RETURN
ENDIF

nSuccess := oMailman:CloseSmtpConnection()
IF (nSuccess != 1)
    ? "Connection to SMTP server not closed cleanly."
ENDIF

? "Successfully sent email using Gmail with a service account key."

oFac:destroy()
oGAuth:destroy()
oTlsSock:destroy()
oMailman:destroy()
oEmail:destroy()