Question

I just started exploring Java Servlets and JSP and am a little confused about the sessions object. Inside a servlet I have this:

public class SampleServlet extends HttpServlet {

    public void doPost(HttpServletRequest request, HttpServletResponse response)
    throws IOException {

        HttpSession session = request.getSession(true);
        session.setAttribute("_session", "_value");
                response.sendRedirect("page2.jsp");         
        }
}

Now, inside page2.jsp, there is a session object as well, but when I do this

<%
out.print(session.getAttribute("_session"))
%>

it does not seem to get the value (as if it is not set). I tried setting a boolean attribute to true but in the jsp page it returns a false. Can someone tell me the right way of doing this? As to what I am trying to do, I want to share some session variables.

Answer 1

Use request.getRequestDispatcher().forward() instead of response.sendRedirect();

So your code would be:

 HttpSession session = request.getSession(true);
 session.setAttribute("_session", "_value");
 request.getRequestDispatcher("page2.jsp").forward();     

Basically, response.sendRedirect() does not preserve session info, so it’s not there when the jsp gets it. request.forward() does preserve the session.

See http://www.coderanch.com/t/170618/java-Web-Component-SCWCD/certification/sendRedirect-Vs-requestdispatcher-forward