Re: [Simple-support] How to handle an empty XML element, when using a Converter via "@Convert"

[Niall G. <gal...@ya...>]

Sounds like a good idea

--- On Tue, 26/2/13, Timo Rumland <tim...@di...> wrote:

> From: Timo Rumland <tim...@di...>
> Subject: Re: [Simple-support] How to handle an empty XML element, when using a Converter via "@Convert"
> To: sim...@li...
> Received: Tuesday, 26 February, 2013, 11:43 PM
> Hello Niall,
> 
> > Looks like a bug to me, ill take a closer look at it.
> If it's a bug ill
> release a fix for it shortly.
> 
> thanks a lot for your answer!
> 
> Now in my opinion, a Converter should be allowed to return
> null (or a
> "Value" instance with its "value" property to be null).
> 
> I could imagine, that there are circumstances, where a
> special value in a
> XML tag must be converted to "null" in the
> target/deserialized object. So
> allowing a converter to convert to null would enhance the
> flexibility (you
> could write a converter which converts
> <time>null</null> to Java's 'null' in
> the deserialized object).
> 
> 
> Best Regards,
> Timo
> 
> 
> -----Ursprüngliche Nachricht-----
> Von: Niall Gallagher - Yieldbroker [mailto:Nia...@yi...]
> 
> Gesendet: Dienstag, 26. Februar 2013 23:21
> An: Timo Rumland; sim...@li...
> Betreff: RE: [Simple-support] How to handle an empty XML
> element, when using
> a Converter via "@Convert"
> 
> Looks like a bug to me, ill take a closer look at it. If
> it's a bug ill
> release a fix for it shortly.
> 
> -----Original Message-----
> From: Timo Rumland [mailto:tim...@di...]
> 
> Sent: Wednesday, 27 February 2013 4:42 AM
> To: sim...@li...
> Subject: [Simple-support] How to handle an empty XML
> element, when using a
> Converter via "@Convert"
> 
> Hello,
> 
> I have the following situation: I'm using the @Convert
> annotation with my
> own converter implementation on a class field named "time".
> 
> When I now try to deserialize XML, which contains that
> "time" element but is
> empty like this:
> 
> ----
> <time></time>
> ----
> 
> my converter will be called and the SimpleXML framework
> throws an exception:
> 
> ----
> [...]
> Caused by: java.lang.NullPointerException  at
> org.simpleframework.xml.convert.Reference.getType(Reference.java:70)
> ----
> 
> This is because my Converter implementation returns "null",
> when the XML
> element is empty. As the javadoc for "Converter.read" tells,
> it is not
> allowed to return "null".
> 
> But now my question is, how should I handle the situation,
> where I use a
> Converter which is "confronted" with an empty XML element?
> 
> Looking at the Method
> 
>  
> "org.simpleframework.xml.convert.AnnotationStrategy.read(Type,
> NodeMap<InputNode>, Value)"
> 
> We can see the following code snipped:
> 
> ----
> if(converter != null) {
>   Object data = converter.read(parent);
>          
>   if(value != null) {
>     value.setValue(data);
>   }
>   return new Reference(value, data);
> }
> ----
> 
> This means, that if there is a @Converter defined, it gets
> called in any
> case, even if the value of that XML element is empty/null.
> But at the same
> time, Converter.read(...) should not return "null".
> 
> I think the "AnnotationStrategy" class should handle this
> situation,
> checking for an empty XML element, so the converter gets not
> called in that
> case.
> 
> 
> So, what is the correct way to handle such a situation, or
> is it a
> "drawback" (maybe even a bug) of the "AnnotationStrategy"
> class?
> 
> 
> Thanks a lot for your help!
> 
> 
> Best Regards,
> Timo
> 
> 
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