Re: mod rewrite, RequestDispatcher and intercepting requests to the server
On Tue, 6 Mar 2001, frederic barachant wrote: I also have the idea of doing this, and thought that we could make all accesses create a 404, simply by having an empty site) then, by having all of them going to a servlet, you would do the first part. (interception) By moving the http port of Apache to an other, we could, after rewriting, recreate the request, and send it directly to it. There would be no collision problem. The problem to achieve this is: How to redirect 404 to a single servlet? You can use the error-page element in server.xml to map errors or exceptions to the path of a resoruce in the web application. See page 67 of the Servlet 2.2 spec. -- Brett http://www.chapelperilous.net/~bmccoy/ The Fifth Rule: You have taken yourself too seriously. - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, email: [EMAIL PROTECTED]
Re: mod rewrite, RequestDispatcher and intercepting requests to the server
--- Michael Tickle [EMAIL PROTECTED] wrote: I am attempting to intercept all requests to a server so I can extract information from the header. I would then like to pass the request on to the server for it to display the user the requested page. Sounds straightforward. I am led to believe that TomCat can not direct all requests to it on to a servlet - is this correct? Uh? What exactly are you trying to say here? If you are saying that tomcat can not be configured to send every single request all to the same servlet, then I'm not sure that's true. Couldn't you setup servlet pattern-mapping like so: servlet-mapping servlet-name DelagatorServlet /servlet-name url-pattern / /url-pattern /servlet-mapping servlet-mapping servlet-name DelagatorServlet /servlet-name url-pattern * /url-pattern /servlet-mapping You may need a couple of other patterns like "/*.*" or "/*/*" as I'm not sure of the exact behavior of the wild-card algorithm used in TC. You may also want to define your own context for "webapps/" to intercept activity there from going to webapps/ROOT instead of to your application context. I won't claim that this is simpler or better than just using Apache's rewrite module. It is recommended you use apache anyway for serving static content, so it may be simplest to just settup some RewriteRules to do this (funnel all requests to a single servlet). I have installed apache and using mod rewrite all requests are forwarded on to my servlet. The servlet the extracts the header information. The problem then is showing the user the requested page. Ideally I would just like to return the request to the server and let it deal with it. I am told the closest to this is RequestDispatcher. However RequestDispatcher seems only to be able to use relative linking - this will not work for me as I want to go from http://win2k:9090/servlet/myservlet?To=/index.html to http://win2k/index.htm Firstly is there a better way of doing what I am trying to do? You want to use the HttpServletResponse.sendRedirect() method instead of RequestDispatcher.forward(). The forward() method only accesses urls reachable in the current servlet engine thus they must be relative URLs or 'absolute' relative to the current servlet context path. The sendRedirect() method is an actual HTTP redirect that tells the browser to go somewhere else. Keep in mind that neither a forward() or a sendRedirect() will work once the response has been committed, which can happen if you modify request headers or write more output to the response than the buffer size (8k I believe). Secondly is there a similar feature to RequestDispatcher that can use full URLs not relative URIs? HttpServletResponse.sendRedirect() Thirdly has TomCat got any rewrite functionality (CF mod rewrite) since if I can not pass the request back to the apache domain I will have to somehow rewrite all the URLs in the tomcat domain. TOmcat has pretty minimal rewrite capability (basically the servlet-naming tag above). This sounds like a prime candidate for an Interceptor for a future version (ideally it work consistently with apache mod_rewrite rules in effect) but is not trivial and probably won't happen real soon. However, as indicated above, you should be able to solve your problem by using sendRedirect() to send the requests back to apache (or wherever). Cheers, Mel __ Do You Yahoo!? Get email at your own domain with Yahoo! Mail. http://personal.mail.yahoo.com/ - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, email: [EMAIL PROTECTED]
Re: mod rewrite, RequestDispatcher and intercepting requests...
In response to Mel Martinez...
Basically what I am trying to do is build a web counter that is session
aware. I want to write a log file with request page, referring page, date,
time, user agent and session id.
I am currently using apache to sent all requests to my servlet with
RewriteRule ^(.*)/(.*) http://win2k:9090/servlet/redirect?To=/$2 [R,L]
so my servlet gets the parameter To and knows what page the user requested.
There are only two problems with my implementation so far (aside from the
fact I have not started the session tracking) first is serving the page to
the visitor. I have managed this with requestdispatcher but that caused the
second problem tomcat does not then rewrite the links.
I just tried
response.sendRedirect("http://win2k/index.html");
but that does not work with my rewrite rule as the page is redirected back
to the servlet. I was informed that this would not happen with
RequestDispatcher.
I am about to look in to the servlet mapping, but would that allow me to
preserve the identity of the requested page like the apache rewrite rule
does?
Could I possibly use HttpUtils() getRequestURL(HttpServletRequest req) to do
what I am after? Failing that I am thinking of manually opening the file
and writing it out to the visitor - would that work??
The other option I can think of is to turn all the HTML pages in to JSP and
have the JSP collect the information (request page, referring page, date,
time, user agent and session id) and send it to a servlet - would that be a
better way of doing it?
Thanks for any help
Mike
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Michael Tickle
Computing Science
Dept. of Computation
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Re: mod rewrite, RequestDispatcher and intercepting requests...
--- Michael Tickle [EMAIL PROTECTED]
wrote:
I am currently using apache to sent all requests to
my servlet with
RewriteRule ^(.*)/(.*)
http://win2k:9090/servlet/redirect?To=/$2 [R,L]
so my servlet gets the parameter To and knows what
page the user requested.
That needs to have some more 'smarts' added to it.
I just tried
response.sendRedirect("http://win2k/index.html");
but that does not work with my rewrite rule as the
page is redirected back
to the servlet.
Of course it won't! Your rewrite rule is immediately
forwarding it 'back' to the servlet! :-)
1) request comes to apache
2) your rewrite rule sends it to tomcat servlet
3) tomcat servlet redirects it to apache
4) repeat at (2) !!!
You need to put some clue to the Rewrite Engine to
tell it that you don't want a URL to be rewritten
further.
I would suggest that you preprocess the url in your
servlet before you do the sendRedirect to embed some
clue such as rewriting it as:
http://win2k/index.html -
http://win2k/index.html?DELEGATED=true
or whatever. Next, modify your rewrite rule to have a
conditional:
RewriteCond $0 !.*/DELEGATED.*
RewriteRule ^(.*)/(.*)
http://win2k:9090/servlet/redirect?To=/$2 [R,L]
This will make your rule skip any URL with the 'clue'
you've embedded.
Next, apply a rule to remove the 'clue'
RewriteCond $0 .*/DELEGATED.*
RewriteRule (.*)/DELEGATED(.*) $1$2
don't redirect this time or you'll just jump back into
the cycle.
Alternatively, you might just add a query string param
or set some other request info to act as your 'clue'.
Still another alternative is to simply run another
Apache server instance or virtual host that does NOT
apply your rewrite rule. There are lots of
strategies. Use your imagination. :-)
I was informed that this would not
happen with
RequestDispatcher.
??? RequestDispatcher will only forward or include
requests to be serviced in the same servlet engine.
It can not redirect back to apache.
The other option I can think of is to turn all the
HTML pages in to JSP and
have the JSP collect the information (request page,
referring page, date,
time, user agent and session id) and send it to a
servlet - would that be a
better way of doing it?
It depends on your application. I don't really have a
clear idea on what your high-level goal is here.
Good luck,
mel
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