Question

Is it possible to have the same servlet perform validation? It seems that one might have to utilize some sort of recursion here, but when I type in something in the e-mail box and click submit the e-mail parameter is still blank.
After I click submit, the URL changes to: http://localhost/servlet/EmailServlet?Email=test

The page shows Email: null and the text box, but I was expecting it to go through the validation function (i.e. not be null). Is it possible to achieve this type of recursive behavior?

public class EmailServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, 
            HttpServletResponse response) throws ServletException, IOException 
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        String theForm =
            "<FORM METHOD=\"GET\" ACTION=\"EmailServlet\">\n<INPUT TYPE=\"TEXT\" NAME=\"Email\"><P>\n" 
            + "<INPUT TYPE=\"SUBMIT\">\n</FORM>";
        String email = (String) request.getAttribute("Email");

        // Bogus email validation...
        if( email == null )
        {
            out.println("Email: " + email + "\n" + theForm);
        }
        else if(emailAddressNotBogous(email))
        {
            out.println("Thank you!");
        }
        else
        {
            out.println("“Invalid input. Please try again:\n" + theForm);
        }
        out.flush();        
    }
}

Update: as the accepted answer pointed out, there was an error in the code. Changing the getAttribute to getParameter fixes the “problem” :).

String email = (String) request.getAttributegetParameter(“Email”);

Answer 1

To get a form parameter in a servlet you use:

  request.getParameter("Email");

And yes you can use the same servlet but it would be way easier to use two different servlets to do this.