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From Carsten Ziegeler <cziege...@apache.org>
Subject Re: Experimental per-sitemap reloadable classloader
Date Wed, 09 Mar 2005 10:27:27 GMT
Sylvain Wallez wrote:
> Hi all,
> 
> Having to often write quick prototypes with Cocoon, I have on my laptop 
> one main Cocoon installation and a lot of subsitemap directories in 
> various locations, all mounted into the main Cocoon using the 
> mount-table matcher.
> 
> That works fine until the prototypes need some specific classes, as I 
> then hit the problem of deploying these classes. Some ant tasks 
> automatically copy the corresponding jars in the main WEB-INF/lib, but 
> that's really not convenient.
> 
> So I wrote in 2.2 an experimental per-sitemap classpath that allows each 
> sitemap to define its own specific classpath for the components defined 
> by <map:components>.
> 
> The syntax is as follows (the sitemap is in src/webapp hence the "../..").
> <map:components>
>   <map:classpath>
>     <class-dir src="../../build/eclipse"/>
>     <lib-dir src="../../lib"/>
>   </map:classpath>
>   <!-- other components -->
> </map:components>
> 
> A side benefit, tremedously useful, is that the classloader is 
> re-created when the sitemap is reloaded. So this allows, by setting a 
> class-dir, to reload changed classes simply by touching the sitemap.
> 
> Maybe not as smart as an automatic compiling classloader, but as saving 
> in Eclipse automatically recompiles the classes, the productivity boost 
> is impressive, especially when combined with the component lazy-loading 
> mode.
> 
> This feature is intended for application development-time, as it doesn't 
> take into consideration instances of the previous versions of the 
> reloaded classes that may be stored here and there such as in session 
> attributes. That means that you may get some ClassCastException whenever 
> such a cases arises. This is the current price to pay for fast roundtrips.
> 
Great!!

What about using this for blocks - a simple version - as well? So we
could just drop a block of functionality (or a web app) into Cocoon. The
sitemap has the includes for the components and this extra classpath.

For reloading: when the sitemap is reloaded, the classloader could only
reload those classes/jars that have changed since the last load/reload.

WDYT?

Carsten
-- 
Carsten Ziegeler - Open Source Group, S&N AG
http://www.s-und-n.de
http://www.osoco.org/weblogs/rael/

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