title: JSF concurrency issue
body: <p>When i hit a link a window popup is opened.I am having a session managed bean that loads a java.util.List.It is taking few seconds to load that list.</p>
  
  <p>when i click the link twice i am getting concurrent modification exception. because the page is in session mode and first request is still loading the List, before it ends the second request tries to update the list.</p>
  
  <p>I have two possible solution in hand</p>
  
  <p>1) introducing synchronized block</p>
  
  <p>Question : Introducing synchronized block leads to performance issue in multithread environment?</p>
  
  <p>2) javascript to disable the link once it clicked.</p>
  
  <p>problem : Not a good option because we need to restore the state of javascript once the popup is loaded. There is a possibility that the link is disabled forever if the popup window terminated abnormally.</p>
  
  <p>Is there any other solution for this issue?</p>