Hi Marton. Yes, you need to explicitly call setAttribute() when you modify
any object in the session. Otherwise, the object won't be updated in App
Engine's cache/datastore, which are the mechanisms it uses to back sessions
- Jason
On Thu, Sep 3, 2009 at 2:11 AM, Marton Papp <mapr...@gmail.com> wrote:
>
> Hi!
>
> I am using HttpSession to store some information as session
> attributes. When I am testing the application locally, it works fine.
> But when I upload it to production, it seems that any session
> attributes that I retrieve from the session and modify it are not
> persisted back to the session again, unless I specifically call
> HttpSession.setAttribute() in each request. I am not sure whether it
> is the expected behavior or it is bug. Here are the two test cases:
>
> Test1:
>
> public class Test_gae_sessionServlet extends HttpServlet {
> private static final String SESSION_ATTRIBUTE_NAME =
> "test_session_attribute";
>
> public void doGet(HttpServletRequest req, HttpServletResponse resp)
> throws IOException {
> HttpSession session = req.getSession();
> resp.setContentType("text/plain");
>
> SessionContext sessionContext = (SessionContext)
> session.getAttribute
> (SESSION_ATTRIBUTE_NAME);
>
> resp.getWriter().println("session retreived: " +
> sessionContext);
>
> if (sessionContext==null) {
> sessionContext = new SessionContext();
> resp.getWriter().println("session created: " +
> sessionContext);
>
> // calling setAttribute only when the object is
> first created
> resp.getWriter().println("putting context into
> session: " +
> sessionContext);
> session.setAttribute(SESSION_ATTRIBUTE_NAME,
> sessionContext);
> }
>
> sessionContext.value++;
>
> resp.getWriter().println("context at end of retquest: " +
> sessionContext);
> }
> }
>
>
> Test2:
>
> public class Test_gae_sessionServlet extends HttpServlet {
> private static final String SESSION_ATTRIBUTE_NAME =
> "test_session_attribute";
>
> public void doGet(HttpServletRequest req, HttpServletResponse resp)
> throws IOException {
> HttpSession session = req.getSession();
> resp.setContentType("text/plain");
>
> SessionContext sessionContext = (SessionContext)
> session.getAttribute
> (SESSION_ATTRIBUTE_NAME);
>
> resp.getWriter().println("session retreived: " +
> sessionContext);
>
> if (sessionContext==null) {
> sessionContext = new SessionContext();
> resp.getWriter().println("session created: " +
> sessionContext);
> }
>
> // calling setAttribute in every request
> resp.getWriter().println("putting context into session: " +
> sessionContext);
> session.setAttribute(SESSION_ATTRIBUTE_NAME,
> sessionContext);
>
> sessionContext.value++;
>
> resp.getWriter().println("context at end of retquest: " +
> sessionContext);
> }
> }
>
>
> The object stored in the session:
>
> public class SessionContext implements Serializable {
>
> private static final long serialVersionUID = -5151175222401820614L;
>
> public int value = 0;
>
> @Override
> public String toString() {
> return "SessionContext [value=" + value + "]";
> }
>
> }
>
>
> In Test1 it is always the first version of the SessionContext that is
> retreived in each request, no matter that I try to change its contents
> during each request. Test2 works as expected. Is it so that I need to
> call HttpSession.setAttribute() for any object that is expected to
> change during the request? Is it according to the servlet
> specification?
>
>
> Marton
>
> >
>
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