title: Vaadin authentication best practice
body: <p>I am interested in the best practice in authentication in Vaadin I think there is mainly two option here:</p>
  
  <ul>
  <li>ThreadLocal (can cause Out of memory, can have the same thread for different users)</li>
  <li>Spring Security + Vaadin integration (seems a little too much)</li>
  </ul>
  
  <p>Which one do you prefer and why? 
  (Security issues, easy development, other factors)</p>