If you invoke main.jsp, the RequestProcessor IS NOT invoked. Well, not
unless you've mapped in to .jsp.
Most people tend to map ActionServlet to .do, and I think extension
mapping is probably more prevalent than path mapping. This is done in
web.xml, same as any servlet mapping is. Remember that ActionServlet is
invoked by a request for a resource mapped to it, and it in turn invokes
RequestProcessor to, well, process the request! :)
So, the answer to your question is simply that Struts is not involved
when you request a resource that doesn't map to ActionServlet.
On to the second question... you asked what happens when
RequestProcessor.process() returns null... well, first of all, that
method doesn't return anything (I'm looking at 1.2.4 source, but I don't
believe it's any different in 1.2.7).
The long answer is that the forward or redirect was already done, if
applicable, by the call to processForwardConfig(). Now, maybe your
thinking what happens if an Action returns null? This is actually a
perfectly valid result of an Action execution. This indicates to Struts
that the response is already fully formed that no forward or redirect
should occur.
About processCachedMessages()... I think the thing to keep in mind is
that ReqestProcessor is something that ActionServlet delegates to in
order to service a request. With that in mind, it's not incorrect to
almost view ActionServlet and RequestProcessor as two parts of the same
larger whole (i.e., you could simply incorporate RequestProcessor into
ActionServlet and have it work the same). They are separate so as to
represent an extension point in the framework (i.e., custom request
processors and/or custom ActionServlets, independant of each other).
Further, with all that in mind, asking whether it would be better suited
to being called in ActionServlet is almost an invalid question... it
doesn't much matter :) You could take anything that's in
RequestProcessor and put it in ActionServlet, assuming you kept all the
ordering of events correct and such, and it would work just as well.
It's a question of being extensible and architecturally sound is all.
I wasn't sure what you were getting at with regard to a dummy action...
it sounds like you might be trying to use PHP instead of JSP, is that
right? If so, I don't know much about PHP frankly, but I remember a
discussion with regard to doing that a few months back and I was told
then that PHP is a bit different than JSP, a I recall, it's almost more
like Struts than JSP, and therefore there is a bit more to it than
simply forwarding to a PHP page. Maybe someone with more PHP knowledge
than me (since I have virtually none, it should be easy to find!) can
answer this better.
Lastly, about your question asking why a loop doesn't occur when an a
forward is returned... can you describe why you think it would? That
might be easier than trying to explain why it doesn't happen :)
Frank
devosc wrote:
Hi,
I've been looking at the src of v1.2.7.
I think the real question is, what happens when no action is invoked,
or configured in the struts xml file.
For example, the initial request is to main.jsp which has no
associated mappings in the xml config file, how does the
RequestProcessor (or RequestDispatcher) then know how to handle this
request ? e.g. it seems to magically know when an ActionConfig::path
is not actually intended to be processed as an actual action but just
to load the target jsp script.
Because as far as I can tell unless one of the action mappings has an
unkown attribute set to true then RequestProcessor::processMapping
will throw an error.
Another, possible way of considering it, is what happens when the
RequestProcessor::process method actually returns null...
There might be some semantics occuring here that I'm not experiencing
since what I'm doing is coding the RequestProcessor for the PHP
environment, so I might be over looking, or not experiencing something
while just reading the source code...
As far as I can tell, this morning, I need to have either, a dummy
action that will then echo/print a response to the screen, of have a
seperate web page that is not loaded/controlled by the
RequestProcessor ? The latter doesnt seem feasible.
Another unrelated question, but might help my understanding, is why
does the RequestProcessor process method call the
'processCachedMessages' method, wouldn't this method be better suited
to be called somewhere in ActionServlet ?
I think bascially what I would like to find out, is how a returned
findForward in Action::execute does not tie the system into a loop...
G.
--
devosc
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Frank W. Zammetti
Founder and Chief Software Architect
Omnytex Technologies
http://www.omnytex.com
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