Java Filter to redirect users who are not logged in to login page

I was trying to make a filter to stop users who are not logged in from accessing certain pages.For this i made a filter class with the following `doFilter` method ``` HttpServletRequest request = (HttpServletRequest) req; HttpServletResponse response = (HttpServletResponse) res; String url = request.getRequestURI(); boolean allowedRequest = false; System.out.println(url); if(urlList.contains(url)) { allowedRequest = true; System.out.println("in list"); } if (!allowedRequest) { Object o = request.getSession().getAttribute("UserInfo"); if (null == o) { System.out.println("Hey i am in"); response.sendRedirect("/login.jsp"); } } chain.doFilter(req, res); } // end of doFilter ``` To allow the pages which doesnot need the user to be logged in i created an arraylist url-list in init() Now a very strange stupid thing is happening. suppose i have two pages home.jsp and dcr.jsp. When i try to access home.jsp without logging in the i am successfully redirected to login.jsp but when i am trying to access dcr.jsp it is not redirected although it enters the loop if(null == o) which i can understand because i am getting that line printed in console.THis is the output that i get in the server This is the output that i get in the server ``` /dcrmaintenance.jsp Hey i am in ``` Which tells me that the null == o was true. The page dcr.jsp accesses a session object and since the user is not logged in it is getting java.lang.NullPointerException as expected but i cannot understand why is the redirection not taking place even after entering the loop.If someone can pt out where i am making a mistake it would be appreciated.