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From Gianny Damour <>
Subject Re: An idea for defining custom valves in config.xml
Date Wed, 15 Oct 2008 10:46:22 GMT
On 15/10/2008, at 4:16 AM, David Jencks wrote:

> That's one of the main missing bits of functionality.  Right now  
> the only way to get the g-p.xml is to use c-m-p or to export the  
> plugin from a server it's been deployed into, or to do something by  
> hand with jar packing and unpacking.
> The biggest problem here, in my mind, is that jsr88 only wants you  
> to have one "plan": to deploy something you get to specify the  
> artifact and one "plan".  Our deployment system is built around  
> jsr88 so we either have to condense the g-p.xml and plan into one  
> "plan" or abandon jsr88.
> At the moment I'm thinking that one satisfactory solution might be  
> to more or less embed the plan into g-p.xml.  Perhaps we could  
> avoid duplicating most of the dependency info by adding the  
> <import> element to the dependencies in g-p.xml.  I guess we'd  
> expect a more or less empty <environment> element in the plan and  
> fill in the dependencies from the g-p.xml when deploying.
> I guess another possibility might be to include the info from g- 
> p.xml in the environment element of the plan.
> I've been thinking about this on and off for a long time and don't  
> have any solution I'm entirely happy with so discussion and more  
> ideas are more than welcome :-)


Another possible solution would be to allow the extension of a given  
configuration by other configurations. This could work like the  
web.xml fragment mechanism of the upcoming servlet specs which allows  
framework libraries to transparently install Web components to the  
baseline components defined by the web.xml DD.

When a configuration starts it looks for complementing configurations  
whose responsibility is to alter the baseline configuration. The  
identification of complementing configurations could be based on a  
simple naming convention scheme, e.g. if the base configuration is  
org/tomcat6//car then all the configurations matching the pattern org/ 
tomcat6-transform-DiscriminatorName//car are identified as  
complementing configurations.

If there are complementing configurations, then the baseline  
ConfigurationData could be passed to them for arbitrary  
transformation, e.g. add, update or remove dependencies. An updated  
ConfigurationData is passed back and actually loaded by the kernel.

The main drawback of this approach is the added configuration  
complexity. The main benefits is that it provides application server  
configuration traceability and a mean to perform very simple changes  
to a baseline configuration w/o having to redefine in its entirety  
the configuration to be slightly changed.

In another thread about scripting language integration, I suggested  
an even simpler approach whereby a script is executed to perform  
ConfigurationData transformations.

If any of these two options are plausible solutions, then I am happy  
to move forward with an implementation.


> thanks
> david jencks

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