Disable browser caching in servlet

Question

I know this question has been asked and answered several times before but the solution doesn't seem to work in my WebApp.

This servlet handles a JSP page on which users can (fictively) buy credits. In the get-method, the servlet requests the current credits of the user from the database to show them on the JSP page. Then the user can choose the amount of credits he wants to buy.

The post method checks which value the user has chosen and updates the value in the database for that user.

After buying new credits, it looks for the user like his credits are not updated because the browser (Google Chrome) caches an old version of the page. Only after a while the user can see his updated credits.

This is my servlet:

<!-- language: lang-java -->

    package Controller.Servlets;

    import Controller.ListenerHelper;
    import Model.Listener;
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;

    /**
     *
     * @author Jens
    */
    public class CreditServlet extends HttpServlet {

    private Listener listener;
    private int credits;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();

        ListenerHelper listenerHelper = new ListenerHelper();

        listener = (Listener) session.getAttribute("Listener");

        credits = listener.getCredits();

        request.setAttribute("credits", credits);

        request.getRequestDispatcher("/listener/credits.jsp").forward(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        HttpSession session = request.getSession();

        listener = (Listener) session.getAttribute("Listener");

        String choice = request.getParameter("plan");

        ListenerHelper listenerHelper = new ListenerHelper();

        int creditsToAdd=0;

        switch (choice){
            case "plan_10":
                creditsToAdd=100;
                break;
            case "plan_15":
                creditsToAdd=150;
                break;
            case "plan_25":
                creditsToAdd=250;
                break;
            case "plan_50":
                creditsToAdd=500;
                break;
        }

        try{
            listenerHelper.updateCredits(listener.getUserID(), creditsToAdd, "add");
        } catch(Exception e){
            request.setAttribute("error", e.getMessage());
        }

        httpResponse.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
        httpResponse.setHeader("Pragma", "no-cache"); // HTTP 1.0
        httpResponse.setDateHeader("Expires", 0); // Proxies.

        response.sendRedirect("store.jsp?success=login");

    }
}

At the top of the JSP page I added these lines:

<%
response.setHeader("Cache-Control","no-store"); //HTTP 1.1
response.setHeader("Pragma","no-cache"); //HTTP 1.0
response.setDateHeader ("Expires", 0); //prevents caching at the proxy server
%>

UPDATE Since I can't answer my own question, I'll just update my question. I found out after some more debugging it's not the browser caching the old result but the database only updating the result after restarting the web app. I'm sorry to have wasted your time with this. I'm still new to programming. I'll try to find out why the database acts like this and post my answer. Thanks for your help.

Please have a look at [Making sure a web page is not cached, across all browsers](http://stackoverflow.com/questions/49547/making-sure-a-web-page-is-not-cached-across-all-browsers) — Braj, May 14 '14 at 18:59

developerwjk · Answer 1 · 2014-12-11T20:08:26.180

1

Notice that in the servlet, before redirecting, you are setting this:

response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");

Then in the JSP after redirection just:

response.setHeader("Cache-Control","no-store"); //HTTP 1.1

Why did you back off of using the more powerful header? What happened to "no-cache, no-store, must-revalidate"?

What you set prior to redirection just disappears. Its as if you didn't even do it. Only what you are setting after the redirection is being sent to the client. So you need to put the more insistent header in the JSP like you did in the servlet.

edited Dec 11 '14 at 20:08

answered May 14 '14 at 18:51

developerwjk

8,335
2
11
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Thanks for your help. I first added the httpResponse.setHeader, that didn't work so I added the response.setHeader to the JSP. That didn't work either so I changed a few values but without result. The setHeaders are just trial and error. – DaanCelie May 14 '14 at 18:55
Or even better, just add this response header in a servlet filter. – Luiggi Mendoza May 14 '14 at 21:11

Braj · Answer 2 · 2014-05-14T19:09:30.597

0

Try with different URL always to make it a new call every time from browser.

This trick will force the browser to fetch the new copy of the JSP because the URL has been changed.

response.sendRedirect("store.jsp?success=login&random_uuid");

You can generate unique id using UUID

UUID.randomUUID().toString()

edited May 14 '14 at 19:09

answered May 14 '14 at 18:50

Braj

44,339
5
51
69

Have you tried with `response.setDateHeader("Expires", -1);` – Braj May 14 '14 at 18:58
Thanks for your help. I added a random_uuid to the redirect but the cache still does it job. Shouldn't the random_uuid be added to the requestdispatcher of the doget method to create a unique jsp page? Anyway I tried that as well but that didn't work either. request.getRequestDispatcher("/listener/credits.jsp?random_uuid").forward(request, response); – DaanCelie May 14 '14 at 19:10
here `random_uuid` must be some value not just a string "random_uuid" – Braj May 14 '14 at 19:12
I have shared you a way to generate a random value. It should be `response.sendRedirect("store.jsp?success=login&"+UUID.randomUUID().toString());` – Braj May 14 '14 at 19:19
I've updated my question. Anyhow, your information was still useful. – DaanCelie May 14 '14 at 19:32

Disable browser caching in servlet

2 Answers2