Question

I have created a basic servlet to handle logins on my web app.

currently its in the form;

index.jsp -> loginServlet -> admin.jsp

Requests are sent over the mapping /login

the problem i have is if you try and access the /login without sending post/get it gives a NullPointerException.

How can you handle request sent directly? or is there a better way to handle this?

Stack trace:

java.lang.NullPointerException
    loginServlet.doGet(loginServlet.java:39)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

---

public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws IOException, ServletException
{
    HttpSession session = request.getSession(true);
    String task = request.getParameter("task");
    if(task.equals("logout")) {
        session.removeAttribute("username");
    } 
    RequestDispatcher dispatcher = request.getRequestDispatcher("/index.jsp");
    dispatcher.forward(request, response);
}

Answer 1

if you try and access the /login without sending post/get

How is that ever possible?

I guess there’s some misconception or bad design going on. Here are some hints to put you on the right track:

1. Put login.jsp in /WEB-INF folder.

2. Rewrite doGet() so that it forwards to that JSP.

3. Keep the login handling job in doPost(). Make sure that it never throws an RuntimeException. Those kind of exceptions are basically developer’s faults. Always check user input on null and never trust user input.

This way the login page will be opened when you call that servlet by a GET request (e.g. directly entering its URL in address bar, following a bookmark, etc and the login handling job will be done when you submit a <form method="post"> inside that JSP.

As a bonus, you get nicer URLs.

See also:

• Our servlets tag wiki page