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From Giacomo Pati <>
Subject Re: [showstopper] NPE in CForms MultivalueJXPathBinding
Date Tue, 22 Mar 2005 11:48:28 GMT

Sylvain Wallez wrote:
> Giacomo Pati wrote:
>> Sylvain Wallez wrote:
> <snip/>
>>> Giacomo, I started merging this with DOMFactory but cannot understand 
>>> how this works. Can you explain?
>>> AFAIK, JXPath calls the factory if the node at path "name" doesn't 
>>> exist. So my understanding is that context.getValue(name) will 
>>> *always* return null. 
>> My debugging sessions showed that context.getValue(name) returs the 
>> "node"
>> JXPath wanted to insert something. So in my debugging session it was 
>> (because
>> I have bound to a Bean) the Collection holding the multi value items.
>>> I saw you just added a test for this condition, but doesn't it have 
>>> the effect of always failing by immediately returning false?
>> I've never had any NPEs during my tests and Marco was right that there
>> is a potential NPE if context.getValue(name) returns a null value. 
>> Thus the
>> test.
>>> Also, what is the effect of 
>>> ((Collection)context.getValue(name)).add(null)? How does adding a 
>>> null value allow JXPath to continue further evaluation of the path?
>> JXPath will replace the null value with the value from the multi value 
>> item
>> it wanted to store but had to call the factory first to create the slot.
> Ok. I still don't really understand (would have just as you to follow 
> this with a debugger!), but I merged the collection and DOM factories.

I've skimmed the JXPath samples, guessed how it could work and used the 
debugger to verify until it was working (actually I've missed the 
existence of the BindingJXPathFactory class).

> Works for me using DOM (the sample is no more broken). Can you 
> cross-check with collections so that we can declare the showstopper solved?

Yup, works for me.


Giacomo Pati
Otego AG, Switzerland -
Orixo, the XML business alliance -

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