Java

OAuth2 for a GMail using a JSON Service Account Key

See more GMail SMTP/IMAP/POP Examples

This example shows how to obtain an OAuth2 access token for Gmail using a Google Service Account and a JSON private key. Once acquired, the access token can be used to send emails. Remember, upon token expiration, this process needs to be repeated to obtain a new token. Note: This procedure is specific to OAuth2 with Google Service Account keys. Chilkat2 Java

import com.chilkatsoft.chilkat2.AuthGoogle;
import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Email;
import com.chilkatsoft.chilkat2.FileAccess;
import com.chilkatsoft.chilkat2.MailMan;
import com.chilkatsoft.chilkat2.Socket;

public class ChilkatExample {

    public static void main(String[] args) {
        // 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.
        FileAccess fac = new FileAccess();
        String jsonKey;
        try {
            jsonKey = fac.readEntireTextFile("qa_data/googleApi/chilkat25-b4214220e565.json", "utf-8");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // 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"
        // }

        AuthGoogle gAuth = new AuthGoogle();
        gAuth.setJsonKey(jsonKey);

        // Specify a scope.
        gAuth.setScope("https://mail.google.com/");

        // Request an access token that is valid for this many seconds.
        gAuth.setExpireNumSeconds(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.
        gAuth.setSubEmailAddress("info@chilkat.xyz");

        // Connect to www.googleapis.com using TLS
        Socket tlsSock = new Socket();
        try {
            tlsSock.connect("www.googleapis.com", 443, true, 5000);

            // Send the request to obtain the access token.
            gAuth.obtainAccessToken(tlsSock);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Examine the access token:
        String accessToken = gAuth.getAccessToken();
        System.out.println("Access Token: " + accessToken);

        // 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.

        // -----------------------------------------------------------------------
        MailMan mailman = new MailMan();

        // Set the properties for the GMail SMTP server:
        mailman.setSmtpHost("smtp.gmail.com");
        mailman.setSmtpPort(587);
        mailman.setStartTLS(true);

        mailman.setSmtpUsername("info@chilkat.xyz");
        mailman.setOAuth2AccessToken(accessToken);

        // Create a new email object
        Email email = new Email();

        email.setSubject("This is a test");
        email.setBody("This is a test");
        email.setFrom("Chilkat Test <info@chilkat.xyz>");
        email.addTo("Chilkat Software", "info@chilkatsoft.com");
        // To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

        try {
            mailman.sendEmail(email);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        try {
            mailman.closeSmtpConnection();
        } catch (ChilkatException e) {
            System.out.println("Connection to SMTP server not closed cleanly.");
        }

        System.out.println("Successfully sent email using Gmail with a service account key.");
    }
}