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From "Simone Tripodi (JIRA)" <>
Subject [jira] Resolved: (DIGESTER-143) Unintuitive, possibly broken behaviour.
Date Fri, 28 Jan 2011 08:28:44 GMT


Simone Tripodi resolved DIGESTER-143.

       Resolution: Not A Problem
    Fix Version/s: 2.2

Sorry if I reply late :(

The CallMethodRule[1] javadoc reports:

??Note that when a constructor is used with paramCount=0, indicating that the body of the
element is to be passed to the target method, an empty element will cause an empty string
to be passed to the target method, not null. And if automatic type conversion is being applied
(ie if the target function takes something other than a string as a parameter) then the conversion
will fail if the converter class does not accept an empty string as valid input.??

The behavior is documented in the rule class instead of the Digester#addCallMethod method.


> Unintuitive, possibly broken behaviour.
> ---------------------------------------
>                 Key: DIGESTER-143
>                 URL:
>             Project: Commons Digester
>          Issue Type: Improvement
>    Affects Versions: 2.1
>         Environment: Linux 64 bits
>            Reporter: i30817
>            Priority: Minor
>             Fix For: 2.2
>         Attachments:
> When one tag is a substring of another tag and both are used as xml patterns, such as:
> "rdf:RDF/pgterms:etext/dc:creator"
> "rdf:RDF/pgterms:etext/dc:creator/rdf:Bag/rdf:li" (instances in a collection of creators)
> the callback to the first is called once with empty strings ("") as the body of the tag
if it encounters a instance of the second tag.
> If additionally the first tag has a argument 
> "rdf:RDF/pgterms:etext/dc:creator rdf:type="Literal"" and you bind things correctly for
a two arguments callback with the text body and the argument value ("Literal"), the callback
of the first will be called with a null rdf:type argument and a empty string as the body.
You can use this to distinguish the bogus callback as a workaround, but requires a additional
bean method and confusing binding too.
> The best thing would be if these empty strings callback were avoidable. I can just test
for empty string in the callback, however, i'm trying also to create assertions on the xml
content (including, no empty strings).
> If the bogus callback must exist, one of the ways to make it obvious and distinguishable,
would be to use null as the default value, instead of "". No xml document will have the computation
null value, unless some very strange java binding is happening, in which case, you're asking
for trouble. "" is even worse, because it is common to both domains.
> So RFE:
> 1) Avoid the bogus callback of the smaller xml tree branch if you can.
> 2) if you can't, use null as a default value instead of the indistinguishable "".
> 3) if 2) document this behavior in the javadoc and the digester FAQ.

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