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Date: Sat, 12 Jun 2004 18:00:02 +0200
From: Sylvain Wallez <sylvain@apache.org>
Organization: Anyware Technologies
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To: dev@cocoon.apache.org
Subject: Re: JXTG and caching
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Vadim Gritsenko wrote:

> Sylvain Wallez wrote:
>
>> Vadim Gritsenko wrote:
>>
>>> Sylvain Wallez wrote:
>>>
>>>> Moreover, you may consider the case of complex pipelines where the 
>>>> actual template depends on the user rights, target browser or 
>>>> whatever else. In that case, the cache information can be different 
>>>> depending on used template.
>>>
>>>
>>>
>>> And for caching to play right with proxies and browsers, Vary header 
>>> (and/or some others) should be set. What mechanism can be used to 
>>> set headers from the JX template?
>>
>>
>>
>> <jx:var name="foo" value="cocoon.request.setHeader('bar', 'baz')"/> ??
>
>
>
> Thought a bit about it... Due to streaming nature of the Cocoon 
> (forget for a second that pipeline's default behavior is to buffer 
> output - default can be changed anyway), this won't work. First 
> startElement() event corresponding to root element is already out, 
> and, under ideal conditions, already written to the output stream.
>
> Thus, this will fail.


You're right. Also, if the pipeline is cached, headers aren't set again. 
Headers must actually be set in setup().

> The only other option I see is to mimic XSP page structure: Introduce 
> root <jx:page/> tag which is *not* printed to the output. Then, 
> everything between the <jx:page/> and first SAX event can perform 
> whatever setup operations needed.


That additional root tag is something I dislike in XSP. Furthermore, a 
valid JX template may not contain any <jx:*> element if only expression 
expansion is used. Adding an additional mandatory root tag breaks this 
simplicity.

Don't know... what about some <jx:header> statements that would be 
allowed only as children of the root element and executed in setup()?

Sylvain

-- 
Sylvain Wallez                                  Anyware Technologies
http://www.apache.org/~sylvain           http://www.anyware-tech.com
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