在Servlet中设置后，HttpSession变量为null

Question

Here's my environment. Windows 7, Tomcat 8.x and Java 7.x I'm writing an application, that has an entry point in the servlet, as opposed to a JSP. In this servlet I create a session, assign a variable to it, and then redirect the user to a JSP page. Here's the JAVA code:

HttpSession session = request.getSession();
logger.debug("Session Id: "+session.getId()+
"New Session? "+session.isNew()+
"Created: "+new java.util.Date(session.getCreationTime()));
  session.setAttribute("implementation", sImplementation);
  session.setAttribute("RequestId", sRequestId);

response.reset();
response.sendRedirect(request.getContextPath()+"/jsp/ProductSelection.jsp");

In the JSP page that I just redirected to I try to retrieve the session attribute that I just set in the Servlet and the value comes back as null, but only the first time that I use the JSP page. If I call it again by resubmitting the URL in the browser then everything works. :O :( Here's the relevant JSP code, the value of sImplementation is null the first time this JSP is hit.

<% System.out.println("Session Id: "+session.getId()+
            "New Session? "+session.isNew()+
            "Created: "+new java.util.Date(session.getCreationTime()));
String sImplementation = (String)session.getAttribute("implementation"); %>

Also if I make an entry point into my system to be a JSP page that does nothing but redirect the user to the Servlet everything works as expected. So the session created in the servlet is not valid until. Only when a JSP page is hit. :(

Lastly I tried using dispatcher.forward instead of response.sendRedirect and the session variable is there, however, the bootstrap framework that I'm using to render my pages do not render properly at all. :( I tried this in both Internet Exploder 11.x and Chromium 33.x

So my question is whether the behavior that I'm seeing is normal and expected or if there's something wrong here and there's a solution out there somewhere? :)

Thanks to all in advance, and let me know if anything is unclear or needs more code.

Answer 1

If im not wrong (I might), you should redirect to your jsp using

request.getRequestDispatcher("ProductSelection.jsp").forward(request, response);

This way it will be the same request and you will be able to get your session. By the way if you are creating sessions on your own you should disable the default session made by all jsp's

<%@ page session=“false”%>

Make me know if it worked. :·)