title: Android: What is transport and jsonFactory in GoogleIdTokenVerifier.Builder?
body: <p>in the blow code, whats is <code>transport</code> and <code>jsonFactory</code> ? (I do not understand)</p>
  
  <p><a href="https://developers.google.com/identity/sign-in/android/backend-auth#using-a-google-api-client-library" rel="noreferrer">https://developers.google.com/identity/sign-in/android/backend-auth#using-a-google-api-client-library</a></p>
  
  <pre><code>import com.google.api.client.googleapis.auth.oauth2.GoogleIdToken;
  import com.google.api.client.googleapis.auth.oauth2.GoogleIdToken.Payload;
  import com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier;
  
  ...
  
  GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(transport /**Here**/, jsonFactory /**Here**/)
  .setAudience(Arrays.asList(CLIENT_ID))
  // If you retrieved the token on Android using the Play Services 8.3 API or newer, set
  // the issuer to "https://accounts.google.com". Otherwise, set the issuer to 
  // "accounts.google.com". If you need to verify tokens from multiple sources, build
  // a GoogleIdTokenVerifier for each issuer and try them both.
  .setIssuer("https://accounts.google.com")
  .build();
  
  // (Receive idTokenString by HTTPS POST)
  
  GoogleIdToken idToken = verifier.verify(idTokenString);
  if (idToken != null) {
    Payload payload = idToken.getPayload();
  
    // Print user identifier
    String userId = payload.getSubject();
    System.out.println("User ID: " + userId);
  
    // Get profile information from payload
    String email = payload.getEmail();
    boolean emailVerified = Boolean.valueOf(payload.getEmailVerified());
    String name = (String) payload.get("name");
    String pictureUrl = (String) payload.get("picture");
    String locale = (String) payload.get("locale");
    String familyName = (String) payload.get("family_name");
    String givenName = (String) payload.get("given_name");
  
    // Use or store profile information
    // ...
  
  } else {
    System.out.println("Invalid ID token.");
  }
  </code></pre>