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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