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RE: XPath filter for SAX in Java
This is remarkably similar to the way Saxon started life,
when it was just a Java SAX library and not an XSLT processor... I got rid of it
because supporting serial and tree-based processing in the same code was getting
too difficult.
I didn't have separate handlers or events for the start and
end tag, I had a single NodeHandler that was notified of both the start and end
events using different method calls.
You probably want to think in terms of the conditions being
XSLT patterns rather than arbitrary XPath expressions. Alternatively, use the
XML Schema subset of XPath. In fact Saxon-SA internally does now
have a mechanism which works very like this, used as part of the
schema validator for evaluating key/unique constraints, and supporting only the
XML Schema XPath subset.
Michael Kay
http://www.saxonica.com/
Hi all,
This sounds like something that would be very
useful, and obvious - and yet after spending quite some time searching I've
yet to find a concrete implementation! I've caught whispers here and there
that it can be done, perhaps by hooking into the Saxon or Xalan libraries, but
in the end it's still elluding me.
So what is it?
I just want to
be able to (in Java - and 1.5 is fine) give an XML document to a SAX parser
and have events fired when certain, pre-registered, XPath expressions are
matched.
To put it another way, I want to layer a set of XPath filters over
a SAX parser.
Naturally only a subset of XPath is meaningful within the SAX
context, and ideally I'd like to see a couple of extensions to cater for the
dynamic nature of SAX parsing (in particular, a way of specifying "node tests"
for closing tags).
An example could be something like (pseudo
code):
SaxPathParser parser = new SaxPathParser();
parser.AddHandler( "/TestDoc/Node1/Node2", new NodeHandler() );
parser.AddHandler( "/TestDoc/Node1/text()", new TextHandler() );
parser.AddHandler( "//Node3/endtag()", new EndTagHandler() );
parser.parse();
I've started an implementation along the above lines
that wraps a JAXP SAX parser, but handling things like the // operator
efficiently is something that I'd rather leave to a dedicated library if
possible.
So does anyone know of an XPath filter for SAX parsers, or
something which achieves essentially the same thing? I really don't want to
have to parse a full DOM tree when I just want to catch a few XPath specified
nodes.
Thanks and best
regards,
[)o
IhIL..
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