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From Joe Germuska <>
Subject Re: [chain] LookupCommand's return value
Date Wed, 16 Feb 2005 17:48:39 GMT
At 9:23 AM -0800 2/16/05, Craig McClanahan wrote:
>On Wed, 16 Feb 2005 08:08:14 -0500, Sean Schofield
><> wrote:
>>  > I'm just hesitant to add a new dependency on my own whim.  JEXL isn't
>>  > very heavy (132 K) but I think people are keen on keeping Chain light
>>  > too.
>>  Keeping chain light would be nice.  I don't know too much about JEXL
>>  personally although I will be investigating it shortly as an
>>  alternative to Velocity for some template stuff I have.  How would you
>>  propose doing it if you didn't use JEXL?
>>  > Joe
>Digester has some limited parameter substitution capabilities that
>could be applied when the chain configuration is being parsed.  Is
>that enough to satisfy the kinds of things you're thinking of that
>might want expressions?

I don't think so, since I'm specifically interested in runtime state. 
"Is the ActionForm in *this* context valid?"   "Look up the command 
with the name matching the value of the 'path' property of the 
current ForwardConfig."  "Look up and execute a command only if the 
current value of context property "unitsOrdered" is greater than 

Again, for some or all of these, one could probably manage with 
judicious use of CopyCommand and LookupCommand, possibly augmented by 
some very simple compiled Java commands which might have properties 
for some configurability.

If there's hesitation to formally add any external dependency to the 
project, then when I get around to writing some of these, I'll just 
put them up somewhere and invite people to have a look.  If people 
don't feel that a compile-time dependency on JEXL (which is small and 
which has seen a 1.0 release) is too great a burden, then I'll do 
them directly in the repository in a package which clearly separates 
them from the dependency-free classes 
(org.apache.commons.chain.impl.expr or 


Joe Germuska       
"Narrow minds are weapons made for mass destruction"  -The Ex

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