XOM API for Processing XML with Java

[Elliotte Harold <elharo AT metalab.unc.edu>]

Steve Loughran wrote:


> the specs use consistent xml prefixes for namespaces, and so I have a
> helper XPathContext that knows all the mappings, it goes hand in hand
> with some resolver thing for Xerces that maps URIs to local resources.
> But what I cant do is go from an XPathContext to a URI, because that
> is not allowed.

So what you need is a single method like this:

public void lookup(String prefix)

This would return null if the context doesn't have a mapping for the 
requested prefix? Is that all you need?

> I understand. But right now you are exposing stuff at package scope
> because you have a clear need at the stuff yourself. That's a sign of
> a need (yours) that isnt open to others (me)

Data encapsulation is a key pillar of object oriented programming. One 
should expect that any class or collection of classes will have private 
parts that are not accessible to the outside world. There are 
programmers who argue that nothing should be private; everything should 
be accessible. I just don;t happen to be one of those extremists.

FWIW, there is no such lookup method in XOM now. It's not that I've kept 
it to myself. It just doesn't exist. The relevant functionality is off 
in Jaxen. Adding it requires new code, not just marking an existing 
method public.

> It would be trivial of me to place some stuff in at the same scope, say
> class XPathContext2 extends XPatchContext
> to access the stuff. so you are left with an conundrum: is
> maintainability of an application made worse by having a public API
> extended, or by having random people adding new classes into the
> nu.xom package then publicly redistributing such extensions in their
> own open source applications?

Not as trivial as you might think. XOM takes some steps to prevent 
precisely that. I'm not sure you can add anything to XOM short of 
forking the code base as Wolfgang has done.

--
Elliotte Rusty Harold  elharo AT metalab.unc.edu
XML in a Nutshell 3rd Edition Just Published!
http://www.cafeconleche.org/books/xian3/
http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/ref=nosim