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Date: Thu, 20 Sep 2007 18:12:57 +0200
From: Grzegorz Kossakowski <gkossakowski@apache.org>
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To: dev@cocoon.apache.org
Subject: Re: Demystification of pipelineComponent trouble
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Vadim Gritsenko pisze:
> Joerg Heinicke wrote:
>> On 19.09.2007 18:22 Uhr, Grzegorz Kossakowski wrote:
>>
>>> As you see, this pipeline just process simple JX template that tries
>>> to access one variable
>>> (status.myTasks) and fails at this point. It must fail (by throwing
>>> NPE) because there is no
>>> status.myTasks variable in OM! It's the flowscript code from myBlock1
>>> that is responsible for
>>> setting it and that's why the only valid way to test my sample:
>>
>> Whether there is a variable set or not, a NPE is never good sign.
>> Shouldn't this case be handled? Spring for example throws a
>> NullValueInPathException instead.
> 
> No. No to exception :)
> 
> I suspect in this particular case (CTemplate) no exception should be
> thrown at all: as far as I understand, Cocoon 2.1 will just return empty
> (or null) value, but will not throw an exception. Examples:
> 
>   ${foo}, ${cocoon.foo}, ${continuation.foo}
> 
> all return empty value, no exception.

That's problem with Jexl not CTemplate or OM (actually it is a Jexl who throws NPE). If you try this
expression:

  ${cocoon.foo.size()}

it will throw NPE because size() is internal Jexl's function that is tried to be applied to null
value. I'm with all of you expecting 0 or null in this case but it's really Jexl's problem.

That's the one amongst many reasons why I much prefer JXPath :P

-- 
Grzegorz Kossakowski
Committer and PMC Member of Apache Cocoon
http://reflectingonthevicissitudes.wordpress.com/