How to implement a login page without code duplication

Answer 1

I haven't used JSP, but in most web app frameworks I've used it is possible to use a variable to toggle and error message in the template. You use the same page for both views, but when it is displayed for a failed attempt, an extra div is inserted with the appropriate message.

Answer 2

You can have your servlet validate the password:

For example:

In the login page jsp:

<%
if(request.getAttribute("passwordError")!=null){
out.print(request.getAttribute("passwordError");
}
%>

In the Servlet

if(request.getParameter("password")!=null&&request.getParameter("password").equals("correctPassword"){
// Redirect to Lobby Page
}

else{
request.setAttribute("passwordError", "Incorrect Password");
// Send back to login page
}

This will then display the password error on the login page, avoiding page duplication and the need to use sessions.

Hope this helps.

Tobias.