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From Rommel Sharma <rsharm...@sapient.com>
Subject RE: Applying mod_perl filters to content served from JBOSS
Date Tue, 26 Jun 2012 13:50:31 GMT
Hi André,

Many thanks for the useful information below that helps me in understanding the working of
the filters and the modules.

Realized the mod jk conflict with mod_perl and removed the SetHandler mod_perl and it worked.

Huge thanks to all the experts on this group for sharing the knowledge!!!

Rommel.



-----Original Message-----
From: André Warnier [mailto:aw@ice-sa.com] 
Sent: Tuesday, June 26, 2012 2:51 PM
To: mod_perl list
Subject: Re: Applying mod_perl filters to content served from JBOSS

Rommel Sharma wrote:
> Hi All,
> 
> 
> 
> I have set up mod_perl filtering as follows:
> 
> <Location ~ "/(staticweb|jbossweb)">
>     SetHandler modperl
>     PerlOutputFilterHandler MyOutputHandlers::CustomFilterResponse
>     allow from all
> </Location>
> 
> staticweb is under htdocs and jbossweb is an app-context deployed in jboss .
> 
> All I am doing is read the response and replace certain strings and send that to the
client making the request.
> 
> It is not working for pages being served from jboss (routed to it via the apache web
server, using mod_jk) whereas it is working just fine for pages served from Apache's htdocs
(being filtered as expected) and access is fine for jboss pages that are not under the filter
Location.
> 

Hi.
I think that your problem here is that by specifying
SetHandler modperl
you are contradicting one of your
JkMount ...
directives, and thus these URLs are no longer being forwarded to Tomcat.

In detail :

Part 1 :

Have a look at this page :

http://tomcat.apache.org/connectors-doc/reference/apache.html

and in particular, the section entitled :  Using SetHandler and Environment Variables

What it tells you, is that instead of using directives like this :

JkMount /jbossweb myworker
JkMount /jbossweb/* myworker

you can use

<Location /jbossweb>
   SetHandler jakarta_servlet
   ...
</Location>

to the same effect.  They are equivalent.


Personally, I prefer the <Location> syntax, rather than the JkMount/JkUnMount, because
:
- if "fits" better with the usual Apache configuration style
- it is clearer in terms of the "precedence" aspect of JkMount over other Apache directives
- it is easier to combine with other Apache-based things, just like you are trying to do 
here, to combine it with a mod_perl filter

But as a side-effect, you can see how specifying

SetHandler jakarta_servlet

or

SetHandler modperl

are mutually exclusive.

By saying "SetHandler xxx", you are telling Apache that, to generate the *response* to 
this HTTP request, it should call the module "xxx".
So, it can be *either* jakarta_servlet (forward this request to Tomcat through mod_jk and

have Tomcat generate the response) *or* modperl (let the embedded perl interpreter 
generate the response, by running whatever perl module is configured as the 
PerlResponseHandler)

Part 2 :

In your case, you probably do not need to specify
SetHandler modperl
in order to run you filter.
As far as I know, you need "SetHandler modperl" only, if the response itself is generated

by a perl module. Which is not the case here, as you want Tomcat/jboss to generate it.

So what I would do in your case is :

a) remove any "JkMount /jbossweb ..." that you may have
b) add a section as follows :

<Location ~ "^/jbossweb">

     SetHandler jakarta_servlet

     PerlOutputFilterHandler MyOutputHandlers::CustomFilterResponse

     allow from all

</Location>

If you have any "JkUnmount" related to that same area, then replace them by lines like
SetEnvIf REQUEST_URI ^/jbossweb/([^/]*)/static no-jk
as indicated in that same Tomcat Connector documentation page

What you are doing above is telling Apache :
- for any request URL that looks like "^/jbossweb" ..
- pass this request to Tomcat, via mod_jk, to generate the response page
- and when the Tomcat response page comes back (from mod_jk), and before sending it back 
to the browser, pass it through my filter module

mod_perl advocacy section :

You are touching here one of the really interesting aspects of using mod_perl with Apache

: you can precisely (like with a surgical scalpel) insert your own module in exactly the 
appropriate point of the Apache request handling cycle, and combine it with other things 
which are not mod_perl based.
Similarly, you could have inserted other mod_perl things in the request cycle, like

<Location ~ "^/jbossweb">
     Order allow,deny
     Allow from 1.2.3.4
     PerlAuthenHandler MyHandlers::MyAAAHandler->authenticate
     PerlAuthzHandler MyHandlers::MyAAAHandler->authorize
     require valid-user

     SetHandler jakarta_servlet

     PerlOutputFilterHandler MyOutputHandlers::CustomFilterResponse

     allow from all

</Location>

and done the access control by Apache, then the user authentication and authorization 
using your own modules, then let the response be generated by tomcat/jboss, and filter the

response when it comes back.


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