[Webmacro-devel] RE: Binary accessor "set" problem

[Keats <ke...@su...>]

An update on a cold thread ...

In playing around with the XmlDemo, I thought I had re-encountered this 
elusive bug.  But then I realized the reason ...

I tried to do something like:

   #set $jdomElement.AttributeValue.Thinga = "mabob"

and I got a NullPointerException.  After looking at the PropertyOperator 
code, the problem was suddenly obvious.  WM will always look for a 
"unary accessor" before a "binary mutator".  In this case, it finds a 
getAttribute() method, which happens to return null, hence the NPE.

Perhaps this is the problem Marc was seeing?

Anyway, it's not clear to me how to "fix" this.

We could catch the exception and then look for a binary mutator before 
throwing.  But this could result in inconsistent behavior.  For example, 
in the above case, if the attribute "Thinga" did exist, you would get an 
error, since you can't assign a String to a JDOM Attribute field.

Alternatively, we could always check for the "binary mutator" first. 
This makes some sense, but there are issues here as well.  It would 
break backwards compatability for anyone relying on the unary-first 
behavior.  This probably wouldn't effect many templates, but if it did 
it could be a puzzling error.  It also might have performance implications.

My feeling is that we should just document the behavior and live with 
it.  But if anyone feels strongly that this is bad, I'm open to persuasion.

Keats