a question on xsp and a question on parameterizing xslt

[Donald Ball <ba...@webslingerZ.com>]

hi guys, long time no see. if anyone's curious where i've been, see the
apologetic post to cocoon-dev i just sent in. now, on to my questions. :)

1. a long while back, we had some discussion on whether or not one should
be able to send a redirect from an xsp page. i'd thought the eventual
consensus was that we should, but i guess i was wrong, since the response
logicsheet doesn't seem to provide any way to send a redirect, nor does
the Response interface provide a redirect method. however, one of the c2
docs _does_ reference such a method:

http://xml.apache.org/cocoon/userdocs/concepts/actions.html

compares and contrasts xsp pages and actions. the xsp page it contains has
the following snippet:

<esql:connection>
<esql:dbpool>mypool</esql:dbpool>
<esql:execute-query>
<esql:query>SELECT userid FROM users
        WHERE name=<esql:parameter>name</esql:parameter>
AND password=<esql:parameter>password</esql:parameter></esql:query>
<esql:row-results>
<xsp:logic>
userid = <esql:get-int column="userid"/>
</xsp:logic>
</esql:row-results>
<esql:no-results>
<xsp-response:send-redirect url="/home"/>
</esql:no-results>
</esql:execute-query>
</esql:connection>

the alleged messiness of the code notwithstanding (;)), it seems to be a
common development idiom to want to redirect the user to a different url
or pipeline if something goes awry in an xsp page (the user can't login to
the database, the user doesn't have permission to do something, etc.) if
one cannot send a redirect from an xsp page in c2, can one switch
pipelines based on a flow control statement in an xsp page?

naturally, i can see that one could refactor and use actions to do the
pipeline switching and/or redirecting instead, but i still can't see any
good reason to prohibit early exit from a pipeline, via sendRedirect or
sendError from any component, including xsp pages. it's not always
desirable to factor to split the flow control stuff out of xsp pages into
actions. or is it?

2. in developing my own standalone j2ee webapps using trax, i quickly
realized that if you don't know at what url your webapp is going to be
mounted, you can't use absolute links to resources in your webapp, e.g.
images, javascript libraries, etc. but strictly using relative paths in
your xslt stylesheets when referencing those resources is not only a real
pita, it's impossible if that stylesheet if used in the construction of
urls that appear at different depths in the urlspace. the easy solution is
to parameterize the stylesheet with the context path information:

<xsl:param name="contextPath"/>
<img src="{$contextPath}/images/foo.png"/>

i presume c2 does not already parameterize stylesheets with this datum by
default. does anyone know how you would easily add that parameter to all,
or a certain class, of xslt transformations? also, i presume that others
have encountered this problem. is there an alternate solution anyone has
used that's better?

- donald


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RE: a question on xsp and a question on parameterizing xslt

[Vadim Gritsenko <va...@verizon.net>]

> From: Donald Ball [mailto:balld@webslingerZ.com]
> 
> hi guys, long time no see. if anyone's curious where i've been, see
the
> apologetic post to cocoon-dev i just sent in. now, on to my questions.
:)

Welcome back! I will try answer you questions...


> 1. a long while back, we had some discussion on whether or not one
should
> be able to send a redirect from an xsp page. i'd thought the eventual
> consensus was that we should,

:)

> but i guess i was wrong, since the response
> logicsheet doesn't seem to provide any way to send a redirect,

Nope.

> nor does the Response interface provide a redirect method.

Same here.

> however, one of the c2 docs _does_ reference such a method:

Outdated. Want to fix them? :)

 
> http://xml.apache.org/cocoon/userdocs/concepts/actions.html
> 
> compares and contrasts xsp pages and actions. the xsp page it contains
has
> the following snippet:

<snip/>

> the alleged messiness of the code notwithstanding (;)), it seems to be
a
> common development idiom to want to redirect the user to a different
url
> or pipeline if something goes awry in an xsp page (the user can't
login to
> the database, the user doesn't have permission to do something, etc.)
if
> one cannot send a redirect from an xsp page in c2, can one switch
> pipelines based on a flow control statement in an xsp page?

Nope, it's too late: train already left the station, pipeline is already
assembled. But. I should say that there are *other* ways of tricking:
put include transformer after your XSP and generate <include/> when
something is goes wrong. Yes, it's not same as redirect, but it's
definitely something.


> naturally, i can see that one could refactor and use actions to do the
> pipeline switching 

Pipeline selection is the term in use :)


> and/or redirecting instead, but i still can't see any
> good reason to prohibit early exit from a pipeline, via sendRedirect
or
> sendError from any component, including xsp pages.

In most cases response is already committed! And it is too late to add a
header to response.


> it's not always
> desirable to factor to split the flow control stuff out of xsp pages
into
> actions. or is it?

It is desirable from long perspective view...

 
> 2. in developing my own standalone j2ee webapps using trax, i quickly
> realized that if you don't know at what url your webapp is going to be
> mounted, you can't use absolute links to resources in your webapp,
e.g.
> images, javascript libraries, etc. but strictly using relative paths
in
> your xslt stylesheets when referencing those resources is not only a
real
> pita, it's impossible if that stylesheet if used in the construction
of
> urls that appear at different depths in the urlspace. the easy
solution is
> to parameterize the stylesheet with the context path information:
> 
> <xsl:param name="contextPath"/>
> <img src="{$contextPath}/images/foo.png"/>
> 
> i presume c2 does not already parameterize stylesheets with this datum
by
> default.

Nope, but (with sitemap syntax modified recently) you easily can add
this to all pipelines:
<map:pipeline>
  <map:act type="my-get-context-path-action">
    <!-- all pipelines goes here -->
  </map:act>
</map:pipeline>


> does anyone know how you would easily add that parameter to all,
> or a certain class, of xslt transformations?

Nothing of this kind


> also, i presume that others
> have encountered this problem. is there an alternate solution anyone
has
> used that's better?

I'm thinking about a transformer that converts context:// into absolute
http://. May be not the best way, but definitely will work (and there is
some URL encoding transformer already in the (IIRC) scratchpad)

> 
> - Donald

Regards,
Vadim


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