Invalidate session in Logout Servlet [duplicate]

Answer 1

In every servlet, check whether Session is null or not. If session is not null then only do the request processing else redirect to login page.

HttpSession session  = request.getSession();

if(Session !=null)
{
try
{      
    // acutal servlet actions

}else
{

  // redirect to login page

 }

Also it would be good if you add null check for session in your above code.

HttpSession session  = request.getSession();
if(session !=null)
try
{      
    session.removeAttribute("logonSessData");
    session.invalidate();                               
    String pageToForward = request.getContextPath();
    response.sendRedirect(pageToForward);           }
catch (Exception sqle)
{
    System.out.println("error UserValidateServlet message : " + sqle.getMessage());
    System.out.println("error UserValidateServlet exception : " + sqle);
}
}else
{
  //session already null/ expired
}