Question

I am trying to use javascript to do something once it detects a change in the session object. However, javascript does not detect the change in the session object after i have called UpdateServlet. All these is done on the same page (ie. there is no refreshing of page)

Please help! Thanks.

index.jsp

<%
     //initial settings
     session.setAttribute("dataUpdated", "false");   

%>
<script>

   $(function() {
         var updates = '<%=session.getAttribute("dataUpdated")%>';

         alert(updates);
         //Shows false even after update

      if (updates=="true"){
          //alert("Updated");
      }



   });
 </script>

UpdateServlet.java

 protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

       HttpSession session = request.getSession();
       session.setAttribute("dataUpdated", "true");
       //session object set to true

}

Answer 1

You have to use Ajax in order to check this change. You could check periodically with setInterval like this:

setInterval(function(){
   //Here goes your ajax call
   $.ajax({
     ...
     type: 'post',
     success: function(data){
        ...            
        if(objectChanged){
           //Do your stuff here
        }  
     }
   });
}, 5000); //Check each 5 seconds

My advice is to do your ajax call with POST method to avoid caching (if it caches, no change will be detected)

Hope this helps. Cheers

PS: I used jQuery cause I saw you were using it on your code