Add support for the Service Account (JWT Bearer) authorization flow.

Author: Eric Koleda

samples/GoogleServiceAccount.gs

@@ -0,0 +1,55 @@
+var PRIVATE_KEY = '...';
+var CLIENT_EMAIL = '...';
+var USER_EMAIL = '...';
+
+/**
+ * Authorizes and makes a request to the Google+ API.
+ */
+function run() {
+  var service = getService();
+  if (service.hasAccess()) {
+    var url = 'https://www.googleapis.com/drive/v2/files?pageSize=1';
+    var response = UrlFetchApp.fetch(url, {
+      headers: {
+        Authorization: 'Bearer ' + service.getAccessToken()
+      }
+    });
+    var result = JSON.parse(response.getContentText());
+    Logger.log(JSON.stringify(result, null, 2));
+  } else {
+    Logger.log(service.getLastError());
+  }
+}
+
+/**
+ * Reset the authorization state, so that it can be re-tested.
+ */
+function reset() {
+  var service = getService();
+  service.reset();
+}
+
+/**
+ * Configures the service.
+ */
+function getService() {
+  return OAuth2.createService('GoogleDrive:' + USER_EMAIL)
+      // Set the endpoint URL.
+      .setTokenUrl('https://accounts.google.com/o/oauth2/token')
+
+      // Set the private key and issuer.
+      .setPrivateKey(PRIVATE_KEY)
+      .setIssuer(CLIENT_EMAIL)
+
+      // Set the name of the user to impersonate. This will only work for
+      // Google Apps for Work/EDU accounts whose admin has setup domain-wide
+      // delegation:
+      // https://developers.google.com/identity/protocols/OAuth2ServiceAccount#delegatingauthority
+      .setSubject(USER_EMAIL)
+
+      // Set the property store where authorized tokens should be persisted.
+      .setPropertyStore(PropertiesService.getScriptProperties())
+
+      // Set the scope and additional Google-specific parameters.
+      .setScope('https://www.googleapis.com/auth/drive');
+}