Re: Hidden Fields in Java Servlets - help!!!

 Hosam Aly <>
Fri, 06 Jul 2007 07:31:01 -0000
On Jul 6, 6:02 am, Dan <> wrote:

Okay -

Pardon if this is a newbie question... but this has been driving me

I am trying to pass a simple hidden field from one servlet to another
servlet... .this is to prevent the second page from being displayed
directly - you have to go through the first page to get to the second

I am using IBM Websphere Studio Application Developer Ver 5.1.2.

Below is my script for my first servlet (the one that you first go to)

public void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException
                PrintWriter out = resp.getWriter();
                out.println("<html>" +
                "<head><title></title></head>" +
                "<body>" +

                "<form action=\"/MyWebApp/DirectIt1Servlet2\" method=\"get\"`>" +
                "<input type=\"hidden\" name=\"sw\" value=\"y\">" +
                "</form>" +

                "<p>" + "Below is a button link to the correct page that you want.
You cannot get there any other way besides clicking on the link <br />below:<br />" +

                "<br />" +
                "<a href=\'http://localhost:9080/MyWebApp/DirectIt1Servlet2'>Link" +
"</a>" +
        public void init() throws ServletException

Below is the script to the second servlet (the one that is looking for
that parameter)

public void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException
                        PrintWriter out = resp.getWriter();
                        out.println("<html>" +
                        "<head><title></title></head>" +
                        "<body>" +
                        "<p>Congrats! You made it<br />" +

What the hell am I doing wrong? It keeps reading in sw as null, no
matter what I type.

You're problem looks simple. When your user clicks the hyperlink you
provide in the first page, the user is simply navigating to your
second servlet. The browser wouldn't send a parameter for such a
simple navigation unless it is already in the URL (i.e. "GET"

You need to change your code to "submit" the form. For example, don't
provide the users with a direct URL, but instead provide them with a
button that they can click to take them to the next page, and make the
button of type "submit" (and put it inside the form).

However, if you are concerned about security, I suggest you look for
other ways to do it, because anyone can simply view the source of your
page and find out the parameter you are sending.

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