How to redirect from one servlet to another by using tricky redirection?

Question

If I have two servlets:

@WebServlet (urlPatterns = {"/s1"})
public class Servlet1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) 
    throws ServletException, IOException {

        Map<String, Integer> map = new HashMap<String, Integer>();
        map.put("A", 100);
        map.put("B", 200);
        map.put("C", 300);

        req.setAttribute("map", map);
        getServletContext().getRequestDispatcher("Servlet2").forward(req, resp);
    }
}

public class Servlet2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) 
    throws ServletException, IOException {
        Map map = (Map) req.getAttribute("map");

        for (Object o : map.values()) {
            System.out.println(o);
        }
    }
}

How can I make redirect between them? And which path I need to use in my getRequestDispatcher method? And one more condition - Servlet2 must be without any mapping in annotations or in web.xml.

But I need Servlet2 invisible for user. It cannot access from browser. If I use mapping user can access to the servlet. — user3163426, Jan 06 '14 at 20:38
Are you sure you want Servlet instead of lets say JSP (which is kind of servlet and will not have any annotation or address set in web.xml)? — Pshemo, Jan 06 '14 at 20:38
To bad, because by placing your JSP in `WEB-INF/yourJspFile.jsp` you could dispatch request to it via request dispatcher. Also it would hide this JSP "address" from browsers. — Pshemo, Jan 06 '14 at 20:44

score 3 · Accepted Answer · answered Jan 06 '14 at 20:35

3

Servlet2 must be without any mapping in annotations or in web.xml.

Then you cannot use HttpServletRequest#getRequestDispatcher(String), which is a container managed method that checks those mappings.

That condition is ridiculous and makes no sense. If you aren't going to use the Servlet container, don't make a Servlet. Make a service class that performs the actions you need. You don't need to make everything a Servlet.

Your only (ridiculous) alternative is to instantiate Servlet2 and explicitly invoke its doGet method.

answered Jan 06 '14 at 20:35

Sotirios Delimanolis

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If I need to use mapping in Servlet2, so maybe I can use Filter to cut off every posible request for Servlet2? – user3163426 Jan 06 '14 at 20:55
@user3163426 What is you are trying to do with `Servlet2`? Why does it need to be an `HttpServlet`? – Sotirios Delimanolis Jan 06 '14 at 20:58
It is just a practice. In Servlet2 I print a map. And that's all :) – user3163426 Jan 06 '14 at 20:59
@user3163426 You can practice with `Servlet1`. If `Servlet2` isn't meant to be used as a `Servlet`, don't make it a `Servlet`. – Sotirios Delimanolis Jan 06 '14 at 21:00
But I need my logic to be made with two servlets and redirection mechanism. – user3163426 Jan 06 '14 at 21:01
1

@user3163426 You might _think_ you do, but as it stands, you actually don't. – Sotirios Delimanolis Jan 06 '14 at 21:03
@user3163426 You're welcome. Do a search on how `getRequestDispatcher` works with its `forward()` and `include()` method. That might help you understand when to and when not to use it. – Sotirios Delimanolis Jan 06 '14 at 21:04

How to redirect from one servlet to another by using tricky redirection?

1 Answers1