Quick answer - i dont know how to do an 'early detection' of the user
pressing the stop button. I dont think its possibly - at least I dont think
there is a non-super-difficult way of doing it.
I think you may need to do more than just put your results bean in the
session when providing a means to return results to the user.
For example, what happens if both requests occur successfully ( ie the user
has 2 browser windows open and does 2 successful searches). Seems as though
whatever search finished first will have its results bean overwritten.
In our project we almost exclusively use the request scope to put our beans
in. When the user clicks the 'get me more button' we pass extra parameters
that tell the server to get the next X rows.
eg
user clicks 'find' -> get me the first X rows where ....
user clicks 'more' -> get me the first X rows where primary key is > the
primary key of the last row returned in the previous search.
Basically then each search is independent of the last and you dont have to
worry about cleaning up session beans, overwriting session beans etc.
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Duffey, Kevin
Sent: Thursday, 16 November 2000 8:42 AM
To: Orion-Interest
Subject: Client hits STOP button..is there a way to detect this before
sending a response?
Hi,
I have a need to find out if the connection back to the browser from a
servlet is still good or not, before an attempt to send the response occurs.
Is this possible? I know when I do a response.sendRedirect() or
requestDispatcher().forward() Orion will throw an exception if the
connection to the browser (or client for that matter) has been terminated.
The problem is..I want to check for this before an attempt is made, so that
incase the connection is lost, I don't populate the javabean. I'll give a
reason why this is necessary (and very helpful). I have my code organized
into JSP pages, ControllerServlet/Action classs, JavaBeans and Session
classes. Session classes are STATELESS classes, so that I can get ready to
move to EJB when I get time. Each time a request is submitted, it goes to an
action class method to be handled. The action class instantiates a new
session class (I am not bothering with a pooled setup for session classes at
this point as EJB will do this for me when I move to it). The session class
performs some logic..usually database acitivty of some sort. The action
class is then given a result (usually a Vector of some sort of objects). The
action class then sets a bean variable to point to the vector of results.
The bean is stateful and is session scope (HttpSession). At the end of the
action, the response is forwarded to a JSP page. That page then uses the
bean and its reference to results to display them.
So here is the problem. If a user submits a form (say..to search for all
clients) and lets say that search will take two minutes. 10 seconds later,
the client sees he/she made a mistake on what they were searching for. As if
often the case..they hit STOP on the browser, change their mistake and
submit the form again. On the server..there are now two threads
running..because the first one hasn't completed yet (assuming the user
submitted the form the 2nd time fairly quickly). The 2nd request is
quick..it populates the javabean reference to a Vector of objects say in 20
seconds. The response is sent back and the user sees a list of say 20 items.
Now, while they are looking over this list, the 1st request they sent is
still going on. At some point it too populates the SAME javabean with its
results, which are now different than what the client is actually looking at
on the page. The action tries to return its response but it finds its
connection was terminated. It throws an exception (which I catch), and
voila..the client sees nothing. Where the problem lies though..is when the
first request populates the javabean that the 2nd request already populated.
So when the user clicks on say item 3 of what he sees..it refers to item 3
in the results Vector that has now been replaced with the first requests
results. Therefore, the information is incorrect.
So, what I am trying to do is find a way that if the connection is no longer
available BEFORE the bean is populated and anything else happens, it just
stops in its tracks. That way..if the user submitted another request, the
first one wont repopulate the bean with information that is inaccurate to
what the client is seeing.
Thanks for any ideas and info on this topic.
