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From "simon.kitching@chello.at" <simon.kitch...@chello.at>
Subject Re: [Digester] Can digester match an unknown element?
Date Thu, 27 Mar 2008 09:57:48 GMT
Allen,Eva schrieb:
> We are working with an entity which sometimes adds new xml elements 
> without remembering to tell us about them.  We would like to be able to 
> log a warning whenever we encounter an element that we don't know about.
>
> Is there any way to do this with digester? 
>
> Specifically, we have really simple xml files that in essence, look like
>
> this: 
> <xmlrecord> 
>     <good>acceptedValue1< /good> 
>     <good>acceptedValue2</good> 
>     <bad>rejectedValue1< /bad> 
>         . 
>         . 
>         . 
> </xmlrecord> 
>
> and the digester rules file looks like this: 
> <digester-rules> 
>     <pattern value="xmlrecord"> 
>         do some stuff 
>         <pattern value="good"> 
>             do more stuff 
>         </pattern> 
>         <pattern value="bad"> 
>             do even more stuff 
>         </pattern> 
>     </pattern> 
> </digester-rules> 
>
> All of a sudden one day, we got an "xmlrecord" with an "unworthy" 
> element (names have been changed here to protect the innocent).   We 
> would have liked to log a warning that we didn't know what to do with an
>
> unworthy element, but I can find no way to tell digester how to parse 
> that.  I've tried patterns "xmlrecord/*" and "*/*" but neither one of 
> those works.  I've looked at the digester documentation including the 
> wiki page.  Everybody talks about generalized pattern matching but 
> nobody talks about unknown elements.  Is there any way to do this with 
> digester? 
>
>   

A pattern-matching approach will not work, because it will match nodes
that are *also* matched by other rules.

I don't believe there is any way to do this with Digester at the moment,
but it sounds like a very useful addition, and not too hard to do.
Simply having the Digester object invoke some kind of callback when zero
rules match a node should be fairly easy to add. If you can create a
patch for that, plus unit test, I'll happily apply it.

Alternately, you could create an xml schema for your input file, and set
up the xml parser to do validation. That will allow much more flexible
checking of the input than just "node with no matching rule".

Regards,
Simon




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