Forward to the same JSP page I received the request from (without infinite loop)?

Question

I have a page, productListing.jsp where, you guessed it, I list of products. When a client requests this page, I want the servlet it's mapped to -- ProductsIndexController -- to pull some data from the DB and pass it back to productListing.jsp .

My issue is that because (I assume) I'm forwardin the request to the same page the servlet is mapped to, it's causing infinite redirects and this error javax.servlet.ServletException: AS-WEB-CORE-00089

Is there a way around this? As a quick-fix for now I'm just calling the model methods straight from the JSP page, but I'd rather not do that.

productListing.jsp (as I'd like it to be)

<% 
ArrayList<Product> products = (ArrayList<Product>)request.getAttribute("products"); %>
<!-- Display data by looping over products -->

ProductIndexController (servlet)

@WebServlet({ "/ProductIndexController", "/productListing.jsp" })
public class ProductIndexController extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {       
        try {
            ArrayList<Product> products = Product.all();
            request.setAttribute("products", products);
        } catch (Exception e) {
            Notice notice = new Notice();
            notice.addErrorMessage("Couldn't fetch products: " + e.getMessage());
            request.setAttribute("notice", notice);
        }
        request.getRequestDispatcher("/productListing.jsp").forward(request, response);
    }

Answer 1

What you can do is when you redirect, add a request parameter, say redirected , and set it to redirected in the url, then in your servlet code, just call request.getParamemter("redirected") , then if this request param is present, don't call redirect, otherwise, call redirect

if (request.getParameter("redirected") == null)
    // pay attention to the ?redirected=redirected in the url
    request.getRequestDispatcher("/productListing.jsp?redirected=redirected").forward(request, response)

When that request param is null, you know the request is from your jsp, not the redirected response