XOM API for Processing XML with Java

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

At 5:49 PM +0000 2/2/04, George Richard Russell wrote:
> I'd like to know how to process XML in a streaming manner using XOM. The
> tutorial doesn't mention this (yet, I know) and I can't quite get it
> from the examples / javadoc alone.

Yes, most of the tutorial is scheduled to be writyten during beta. 
Quick version:

Subclass NodeFactory and override the methods you wish to process in 
a streaming fashion. Pass an instance of your NodeFactory subclass to 
the Builder constructor. The most common method to override is 
finishMakingElement(). You can operate on the element passed to that 
method then return an empty Nodes object to keep it from being added 
to the tree. Or if you do want to add it to the tree just call 
super.finishMakingElement(element). There are several examples of 
this in the nu.xom.samples package.  Look for those that begin 
StreamingFoo


> What I'd like to do is process, for example, the item elements and their
> contents from an RSS feed. I'd like to be handed, one at a time, an
> Element with its content, and possibly control the construction of the
> Element to constrain what children are added. So, I'm interested in i.e.
> item's, and the title, link, description child elements with their text
> content. Could I restrict the construction to just these, and how would
> I do so?

Well, I haven't compiled it, but something like this:

private Nodes empty = new Nodes();

public void finishMakingElement(Element element) {

  String name = element.getLocalName();
  if ("title".equals(name)
   || "link".equals(name)
   || "description".equals(name)
   || "rss".equals(name)
   || "item".equals(name) {
     return super.finishMakingElement(element);
  }

  return empty;

}

It can be customized further. Look for the samples with the word 
"Filter" in their class names to see how to do this.


> A _tiny_ buglet ; a typo in the NodeFactory java doc in the spelling of
> instruction.

OK. Exactly where?
--

  Elliotte Rusty Harold
  elharo AT metalab.unc.edu
  Effective XML (Addison-Wesley, 2003)
  http://www.cafeconleche.org/books/effectivexml
  http://www.amazon.com/exec/obidos/ISBN%3D0321150406/ref%3Dnosim/cafeaulaitA