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From David Jencks <>
Subject Re: An idea for defining custom valves in config.xml
Date Wed, 15 Oct 2008 23:59:00 GMT
Hi Gianny,

First, I'd like to make sure I understand the philosophy behind your  
proposals.  IIUC they both involve the idea of making it easy to  
modify an existing plugin rather than making it easy to replace an  
existing plugin with a similar one.

Why is this a good idea?  My idea has been that we should make it  
easier to replace a plugin with a similar one than modify an existing  
one, and then we will have the best of all worlds.

All this being said, I think your ideas are both quite interesting.   
I'm especially interested in the groovy builder approach.

I'll be fairly unavailable until next week but might keep thinking  
about this anyway.

david jencks
On Oct 15, 2008, at 3:46 AM, Gianny Damour wrote:

> 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 :-)
> Hi,
> 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,
> Gianny
>> thanks
>> david jencks

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