title: java.lang.ClassNotFoundException: com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier$Builder
body: <p>I'm trying to add a Google sign-in button in my Java Web Application project. I'm trying to receive in Servlet back-end  an id token using <strong>GoogleIdTokenVerifier</strong>, following Google Guides: <a href="https://developers.google.com/identity/sign-in/web/backend-auth" rel="nofollow noreferrer">https://developers.google.com/identity/sign-in/web/backend-auth</a>. Everything for Eclipse is okay, but running my project using Tomcat v9 and arriving to the point :</p>
  
  <pre><code>final HttpTransport transport = new NetHttpTransport();
  final JsonFactory jsonFactory = new GsonFactory();// tried it with jsonFactory = new JsonFactory();
  GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(transport, jsonFactory).setAudience(id_singleton).build();
  </code></pre>
  
  <p>Eclipse gives me this error: </p>
  
  <pre><code>SEVERE: Servlet.service() for servlet [controller.GoogleTokenSignIn] in context with path [/Project] threw exception [Servlet execution threw an exception] with root cause java.lang.ClassNotFoundException: com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier$Builder.
  </code></pre>
  
  <p>I turned over all the stack overflow and I found an answer which says to update the jars. I have the google api <em><strong>release 1.30.9</strong></em> jars and <em><strong>1.30.6</strong></em> or the <em><strong>oauth</strong></em> and still giving same error.</p>
  
  <p>I don't know how to show my eclipse configuration:
  Run configuration
  <a href="https://i.stack.imgur.com/BzwGO.png" rel="nofollow noreferrer">Server</a>
  <a href="https://i.stack.imgur.com/0bjXz.png" rel="nofollow noreferrer">Arguments</a>
  <a href="https://i.stack.imgur.com/KlyOt.png" rel="nofollow noreferrer">Classpath</a>
  .
  I hope it's clear now.</p>