Question

I am calling a jsp based on 2 parameters which is passed from jsp 1 in this way.Below i pass 2 parameters into 2.jsp and based on these 2 parameters data is displayed in 2.jsp.I have a loop in which i have a number of hrefs like the one i have described below.Each of these href passes a different set of value to 2.jsp.

out.println("<a href=\"2.jsp?prId=" + prog.getId() + count + "\">" + prog.getName() + "</a>");

I retrieve these 2 parameters in 2.jsp using the following lines

count_id = request.getParameter( "country_id" );
prog_id  = Integer.parseInt(request.getParameter( "program_id" ));

Based on these 2 parameters i show the corresponding data in 2.jsp

Now i have a back button in 2.jsp and i call 1.jsp in 2.jsp using the following code

<a href="1.jsp"><img src="/image/back.gif" border="0"></a>

The problem is when i use the back button and go back to 1.jsp and select another href like the one i have described above i get the data related to the previous href selected.

I guess the problem is when i request the page is loaded from cache rather than from the server.
Please advice

Answer 1

You just need to instruct the browser to NOT cache the page. You can do this with help of a servlet filter which sets the following response headers:

@WebFilter("*.jsp")
public class NoCacheFilter implements Filter {

    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) res;
        response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate"); // HTTP 1.1.
        response.setHeader("Pragma", "no-cache"); // HTTP 1.0.
        response.setDateHeader("Expires", 0); // Proxies.
        chain.doFilter(req, res);
    }

    // ...
}

Now just map this filter on an URL pattern covering the JSP pages of interest. E.g. *.jsp or /somefolder/* (the @WebFilter in the example does that for all JSPs).

Make sure that you clear the browser cache before testing.

See also:

• How to control web page caching, across all browsers?