Adrian,
Back in Jan. I was into this very same problem. Scott Boag pointed me to a paper on Incremental XSLT which may be a help to you.
http://www.research.ibm.com/people/v/villard/Papiers/incXSLT.pdf
Now I don't know the answer to your problem but I wanted to point out
what may be another problem. If you change the DOM in the background, the DTM will NOT update so the representation of you document to any of the XPath expressions may not make sense.
There is a method call called getDOMBackPointer which will give you a the real Element from the source document which also may be a help.
You may also want top make your Extension Function into an Extension Element
since the XSLProcessorContext will give you more access than the ExpressionContext.
Hope that helps. John G
Adrian Sutton wrote:
Hi all, (Sorry for the previous email, Outlook decided to send when I tried to paste. Go figure)
I'm looking for a way to get the complete context node list and am generally not getting far. I need the full context node list instead of just the actual context node because I need to rerun XPath expressions dynamically as the user changes the DOM, but can't run the entire XSLT again because of performance issues. I can get the XPath expression, find the context node itself, find all the namespaces in effect, and identify all the nodes which are used in the expression, I just can't get the full context node list. Without the full context node list, functions like position() don't work correctly.
For the record, my current test expression is: my:quantityOrdered * my:unitPrice
but the aim is to support any valid XPath expression.
My first approach was to look for an XPath function or XSLT element I could use to get the full context node list but I haven't found anything.
My second approach was to use a custom function and I've had some success with that. My currrent function is:
public String getContext(ExpressionContext context) { StringBuffer buf = new StringBuffer(); try { DTMIterator iter = context.getXPathContext().getContextNodes(); int handle = iter.getCurrentNode(); if (handle != DTM.NULL) { Node n = iter.getDTM(handle).getNode(handle); while (n != null) { buf.append(XMLFilter.getIDFor(n)); n = getNextNode(iter); if (n != null) { buf.append(","); } } } } catch (Exception e) { log.error("Failed to create context for xpath expression.", e); } return buf.toString(); }
XMLFilter.getIDFor(n) gives a String that can be used to retrieve the node from the DOM later on (though various magic incantations we've discovered). For the first node in the context list this works perfectly, unfortunately it appears that the DTMIterator I'm using is the same one that Xalan is using and so the method causes Xalan to skip over all but the first element (because getContext() has already iterated through the nodes). When I try to reset the position of the iterator I get the exception:
This NodeSetDTM can not iterate to a previous node!>java.lang.RuntimeException: This NodeSetDTM can not iterate to a previous node! at com.ephox.org.apache.xpath.axes.LocPathIterator.previousNode(LocPathIter ator.java:627) at com.ephox.org.apache.xpath.axes.NodeSequence.previousNode(NodeSequence.j ava:364) at com.ephox.org.apache.xpath.axes.NodeSequence.runTo(NodeSequence.java:485 ) at com.ephox.org.apache.xpath.axes.NodeSequence.setCurrentPos(NodeSequence. java:499) at com.ephox.editlive.java2.editor.xml.xpath.XPathExtensions.getContext(XPa thExtensions.java:51)
I notice that there is a DTMIterator.setShouldCacheNodes(boolean) method which enables random access to the iterator but calling it seems to reset the iterator such that it no longer contains any nodes. Is there any property to set to make all iterators random access enabled? I've tried setting:
http://xml.apache.org/xalan/features/incremental TransformerFactoryImpl.FEATURE_OPTIMIZE and http://xml.apache.org/xalan/features/optimize
to false with no success.
Alternately, is there some other approach I'm missing?
Regards,
Adrian Sutton.
-- -------------------------------------- John Gentilin Eye Catching Solutions Inc. 18314 Carlwyn Drive Castro Valley CA 94546
Contact Info [EMAIL PROTECTED] Ca Office 1-510-881-4821 NJ Office 1-732-422-4917
