(DataFlex) Get Google API Access Token using JSON Private Key

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

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

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoFac
    String sJsonKey
    Handle hoGAuth
    Variant vTlsSock
    Handle hoTlsSock
    Boolean iSuccess
    String sAccessToken
    Handle hoMailman
    Variant vEmail
    Handle hoEmail
    String sTemp1
    Boolean bTemp1

    // 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.
    Get Create (RefClass(cComCkFileAccess)) To hoFac
    If (Not(IsComObjectCreated(hoFac))) Begin
        Send CreateComObject of hoFac
    End
    Get ComReadEntireTextFile Of hoFac "qa_data/googleApi/chilkat25-b4214220e565.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

    // 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"
    // }

    Get Create (RefClass(cComChilkatAuthGoogle)) To hoGAuth
    If (Not(IsComObjectCreated(hoGAuth))) Begin
        Send CreateComObject of hoGAuth
    End
    Set ComJsonKey Of hoGAuth To sJsonKey

    // Specify a scope.
    Set ComScope Of hoGAuth To "https://mail.google.com/"

    // Request an access token that is valid for this many seconds.
    Set ComExpireNumSeconds Of hoGAuth To 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.
    Set ComSubEmailAddress Of hoGAuth To "info@chilkat.xyz"

    // Connect to www.googleapis.com using TLS
    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

    // Send the request to obtain the access token.
    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

    // Examine the access token:
    Get ComAccessToken Of hoGAuth To sAccessToken
    Showln "Access Token: " sAccessToken

    // 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.

    // -----------------------------------------------------------------------
    Get Create (RefClass(cComChilkatMailMan)) To hoMailman
    If (Not(IsComObjectCreated(hoMailman))) Begin
        Send CreateComObject of hoMailman
    End

    // Set the properties for the GMail SMTP server:
    Set ComSmtpHost Of hoMailman To "smtp.gmail.com"
    Set ComSmtpPort Of hoMailman To 587
    Set ComStartTLS Of hoMailman To True

    Set ComSmtpUsername Of hoMailman To "info@chilkat.xyz"
    Set ComOAuth2AccessToken Of hoMailman To sAccessToken

    // Create a new email object
    Get Create (RefClass(cComChilkatEmail)) To hoEmail
    If (Not(IsComObjectCreated(hoEmail))) Begin
        Send CreateComObject of hoEmail
    End

    Set ComSubject Of hoEmail To "This is a test"
    Set ComBody Of hoEmail To "This is a test"
    Set ComFrom Of hoEmail To "Chilkat Test <info@chilkat.xyz>"
    Get ComAddTo Of hoEmail "Chilkat Software" "info@chilkatsoft.com" To iSuccess
    // To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

    Get pvComObject of hoEmail to vEmail
    Get ComSendEmail Of hoMailman vEmail To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoMailman To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComCloseSmtpConnection Of hoMailman To iSuccess
    If (iSuccess <> True) Begin
        Showln "Connection to SMTP server not closed cleanly."
    End

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


End_Procedure