public class EmailChecker extends HttpServlet{
   // Udajemy, e jest to baza danych!
   private static List USERS;
   static{
      USERS=Collections.synchronizedList(new ArrayList());
      USERS.add("bruceperry@gmail.com");
      USERS.add("johnjsmith@gmail.com");
      USERS.add("teddyroosevelt@gmail.com");
      USERS.add("janejsmith@gmail.com");

   }
   protected void doGet(HttpServletRequest httpServletRequest, 
         HttpServletResponse httpServletResponse) throws 
         ServletException, IOException {
      String email=null;
      email = httpServletRequest.getParameter("email");
      // Konwersja na typ int, poniewa JavaScript konwertuje
      // na true prawidowy String, taki jak "false".
      int bool = 0;
      if(email != null){

         if(USERS.contains(email)){
            bool=1;
         } else {
            USERS.add(email);   }
      } else {
         // Zgoszenie wyjtku ServletException wskazuje na warto null lub
         // brakujcy parametr.
      }
      sendXML(httpServletResponse,bool);

   }

   protected void doPost(HttpServletRequest httpServletRequest, 
         HttpServletResponse httpServletResponse) throws 
         ServletException, IOException {
      doGet(httpServletRequest, httpServletResponse);
   }

   private void sendXML(HttpServletResponse response,
         int emailUsed) throws IOException {
      response.setContentType("text/xml; charset=iso-8859-2");
      String content = "<?xml version=\"1.0\" encoding=\"iso-8859-2\"?>"+
         "<is_used>"+emailUsed+"</is_used>";
      response.getWriter().write(content);
   }
}
