On Wed, 9 Nov 2005 [EMAIL PROTECTED] wrote:
Hmm, I think the JSF spec has a flaw concerning this. The problem is not
the component itself, but the way the iteration is done. As e result you
are not allowed to:
1. bind the component to session or application scoped backing bean
2. provide a session or spplication scoped DataModel
Synchonizing access to session objects isn't that complicated, but
providing a thread-safe session scoped DataModel is really hard. Silmply
synchronizing isn't sufficent because UIData first sets the row for
processing and then retrieves the data. So you have to save the current
row for every thread. :(
Alternatively you could return a individual DataModel for every thread
sharing the same data.
I considered using database transactions to ensure that concurrent
requests in the same session do not put data stored in the session into an
inconsistent state, but decided it was overkill for my application.
Instead, I used a Servlet filter that synchronized on the session object:
public class SessionSynchronizationFilter implements Filter {
public void doFilter(ServletRequest request,
ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest httpRequest;
HttpSession session;
httpRequest = (HttpServletRequest) request;
session = httpRequest.getSession();
synchronized (session) {
chain.doFilter(request, response);
}
}
public void init(FilterConfig config) throws ServletException {
}
public void destroy() {
}
}
While this should work in principle, I need to implement something closer
to what Vesa Lindfors mentioned earlier in this thread, since double
(multiple) submits are going to get queued up by this code, and the server
is going to appear to be unresponsive if the requests take a significant
amount of time to service.
The following article and source code might be worth looking at for a more
complete solution.
http://www.onjava.com/pub/a/onjava/2004/03/24/loadcontrol.html
I say "should work" above, since I still get "Cannot forward after
response has been committed" errors even with this filter in place.
Jeremy
