Surely the session variable will be reset by the report generation
process, independent of any browser windows open, therefore no problem,
you never need to know if the browser has been closed or not. Or have I
misunderstood?
Brett
Rizwan Merchant wrote:
Thanks for the previous input. I moved the report generation to a thread and
set a session variable which is a boolean indicating that a report is
currently being generated. Once the report generation is complete that
session variable is set to false again.
I have come across another problem though. Say a user starts generating a
report. The boolean session variable is set to true. If the user tries to
generate another report while the fist oneis not complete, then the boolean
variable is checked and the user is not allowed to generate another report
(until the first one is complete and the boolean session variable is set to
false).
In this scenario, if the user abruptly closes the intermediate page which is
supposed to load the report , then the session variable is still set to true
(indicating report is being generated) as the thread on the server has not
finished running. If the user now tries to create another report then s/he
will not be allowed to do so (until the thread on the server is done
running).
So I guess my question is : Is there any way to set a session variable when
the user closes a browser window abruptly?
Or is there another way to approach this problem?
Thanks,
-Riz.
-----Original Message-----
From: Craig McClanahan [mailto:[EMAIL PROTECTED]
Sent: Friday, July 16, 2004 5:23 PM
To: Struts Users Mailing List
Subject: Re: Intermediate loading page
Rizwan Merchant wrote:
Hi Craig,
Thanks for the reply. I came across this solution, but does this not
mean that the user will only be able to generate one report at a time
(since we are storing the flag in the user's session)? If the user
starts generating a second report which is much smaller than the first
then would this not create a problem?
You could accomodate such a thing in several different ways, but how would
the user even start requesting the second report? If they're sitting on the
auto-repeat "Please Wait" page, they won't have the opportunity. If you
want them to be able to go request a second report while the first one is
still generating, you'll probably be better off just navigating back to the
main menu (or something) after firing off the first thread, then let them
fire off a different thread (using a different flag) for the second report
-- then have a screen where they can "pick up" their completed reports and
display them.
If the computational effort to produce reports becomes severe, you might
also consider using some sort of job queueing package so that a single
background thread could do the report generation for all your users (one
report at a time). If you go this way, the "pick up your completed report"
page becomes an even better idea.
Thanks again for your input. Much appreciated.
-Riz.
Craig
-----Original Message-----
From: Craig McClanahan [mailto:[EMAIL PROTECTED]
Sent: Friday, July 16, 2004 3:37 PM
To: Struts Users Mailing List
Subject: Re: Intermediate loading page
Rizwan Merchant wrote:
I am working on a web application using the Struts framework. Using a
form on a jsp page, I generate a report which is displayed in pdf on a
new screen. The report is generated through an Action class method. I
would like to display a "Please wait" screen while the report is being
generated.
The action class method calls functions that generate a pdf file and
then redirects control to that file. So I cannot use the flush()
method to send html to the browser while the report is being generated
(once a response is committed it cannot be written to again). Neither
can I use the 'div' tag method as my new page is not a jsp page (it is
a new browser window with pdf file displayed inside it).
One common strategy for this sort of thing is to refactor your action
into several, along the following lines:
* The Action that is currently creating the PDF should instead
fire off a background thread to do the report preparation. It
will then forward to a "Please Wait" page (see below).
* The background thread should do whatever is needed to prepare
the PDF file, and set a flag variable in the user's session when it's
done,
followed by terminating the thread.
* The "Please Wait" page should say something like "Report generation
in progress", and use a meta-refresh tag to automatically submit
itself
every few seconds, with the destination being a "Done Yet" action.
* The "Done Yet" action will consult the flag variable in the user's
session.
If its not there, forward back to the "Please Wait" page again. If
it's
done, forward to the URL to retrieve the PDF itself.
Craig
My code is shown below....
//the jsp code calling the action
<nested:form action="/reports.do?action=getTransactionReports"
target="_blank">
// The Action class
public ActionForward getTransactionReports(ActionMapping mapping,
ActionForm form, HttpServletRequest request, HttpServletResponse
response) throws Exception {
ICustomerAdministrationClient admin_impl =
getCustomerAdministrationService(request);
//enforce user permission
enforceFeaturePermissions(EMSConstants.FEATURE_REPORTS, request, 1);
EMSBaseAdminForm admin_form = (EMSBaseAdminForm)form; ReportsForm
reportsForm = admin_form.getReportsForm();
//cant do this as it creates an IllegalStateException // PrintWriter
html = response.getWriter(); // // html.print("<html>\n<head><title>my
test</title></head>\n<body>"); // html.print("<p><img
src=\"images/dpt_logo.jpg\"></body></html>");
// html.flush();
// html.close();
//if details type is summary then output format can only be PDF
if(reportsForm.getDetailsType().equals(EMSConstants.REPORTS_SUMMARY))
reportsForm.setOutputFormat(EMSConstants.REPORTS_FORMAT_PDF);
//generate the reports using jasper reports
doJasperReports(reportsForm, request);
CustomerForm customer_form = (CustomerForm)getSessionObject(request,
"customerForm");
Collection all_region_list_forms =
(Collection)getSessionObject(request, "allRegionListForms");
admin_form.setCustomerForm(customer_form);
admin_form.setRegionListForms(all_region_list_forms);
request.setAttribute(EMSConstants.FORM_VIEW, admin_form);
String relativePath = File.separator + "temp_" +
request.getSession().getId(); String pdfFilePath = File.separator +
"temp" + relativePath + File.separator + "ReportinPDF.pdf"; String
csvFilePath = File.separator + "temp" + relativePath + File.separator
+ "ReportinCSV.dpt";
if(reportsForm.getOutputFormat().equals(EMSConstants.REPORTS_FORMAT_PD
F)) return (new ActionForward(pdfFilePath, true));
return (new ActionForward(csvFilePath, true)); }
Any help would be appreciated. Thanks.
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