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Re: XPath filter for SAX in Java

• To: Phil Nash <phil.nash.lists@g...>
• Subject: Re: XPath filter for SAX in Java
• From: Uche Ogbuji <Uche.Ogbuji@f...>
• Date: Thu, 29 Sep 2005 08:32:16 -0600
• Cc: xml-dev@l...
• In-reply-to: <81b2939305091920285f4c979d@m...>
• Organization: Fourthought, Inc.
• References: <81b2939305091920285f4c979d@m...>

On Mon, 2005-09-19 at 23:28 -0400, Phil Nash wrote:
> 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.

FWIW, in a long conversation on this point earlier this year I pointed
out that I had in Amara XML Tools a Python framework for just this
capability.  I thought a couple of Java folks chimed in that they had
similar.  Perhaps look into Nux?


-- 
Uche Ogbuji                               Fourthought, Inc.
http://uche.ogbuji.net                    http://fourthought.com
http://copia.ogbuji.net                   http://4Suite.org
Articles: http://uche.ogbuji.net/tech/publications/

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    • From: Phil Nash <phil.nash.lists@g...>

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