Java

Get OAuth 2.0 Access Token using G_SvcOauthAccessToken2

Obtains an OAUTH2 access token from the Google OAuth 2.0 Authorization Server using the G_SvcOauthAccessToken2 method. This is for Server to server applications using Google API's that need an access token. See https://developers.google.com/accounts/docs/OAuth2ServiceAccount Chilkat2 Java

import com.chilkatsoft.chilkat2.Cert;
import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Hashtable;
import com.chilkatsoft.chilkat2.Http;

public class ChilkatExample {

    public static void main(String[] args) {
        // This example assumes 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
        // --------------------------------------------------------------------------------

        Http http = new Http();

        // 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:
        Cert cert = new Cert();
        try {
            cert.loadPfxFile("/myDir/API Project-1c43a291e2a1-notasecret.p12", "notasecret");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // 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: The email address of the user for which the application is requesting delegated access.
        // numSec: The number of seconds for which the access token will be valid (max 3600).

        Hashtable claimParams = new Hashtable();

        // The required claim parameters that must be provided by the application are
        // the "iss" and "scope" params:
        claimParams.addStr("iss", "761326798069-r5mljlln1rd4lrbhg75efgigp36m78j5@developer.gserviceaccount.com");
        claimParams.addStr("scope", "https://mail.google.com/");

        // The "sub" param is 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.
        //
        // Comment out this line if there is no such email address.
        claimParams.addStr("sub", "user@your-domain.com");

        // The "aud" parameter is optional.  If not set, it defaults to the value shown here:
        claimParams.addStr("aud", "https://accounts.google.com/o/oauth2/token");

        int numSec = 3600;

        String accessToken = null;
        try {
            accessToken = http.gSvcOauthAccessToken2(claimParams, numSec, cert);
            System.out.println("access token: " + accessToken);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
        }
    }
}