We currently use XPathAPI.selectSingleNode() for an application which
extracts data from XML message text nodes based on a set of XPath query
strings.
As part of an investigation to improve performance, we are investigating
using CachedXPathAPI instead. This certainly is a lot faster (as would be
expected) but we are concerned about its safety in a multi-threaded
environment.. The Javadoc for CachedXPathAPI is not quite clear on this
subject, but suggests there may be a problem, as we are changing the source
document but keeping the XPath Strings the same. All of our tests which
attempt to 'force' errors or data corruption by sharing CachedXPathAPI
between threads have so far found no problems.
However I found the below post on the list archives:
> Subject: RE: Using DTMDocumentImpl
> From: Joseph Kesselman <[EMAIL PROTECTED]>
> Date: 2002-10-01 21:48:24
>
> <SNIP>
> (Note that there's a problem if you're changing your DOM between XPath
> queries; DOM2DTM assumes the source DOM is not being altered, and
> violating that expectation can break Xalan. Changing the content of text
> nodes is _probably_ safe, but most other changes wouldn't be, and would
> probably require flushing the DTM from the cache and rebuilding it from
> scratch... and I think our only flush mechanism today is to switch to a
> new instance of CachedXPathAPI. Another of the reasons we're experimenting
> with the DOM2DTM2 approach is that it should be more tolerant of
> alterations in the DOM between XPath scans.)
> <SNIP>
This suggests that text nodes should be OK - but can anyone give a more definitive
answer than _probably_ ?
Or suggest an alternative approach?
If not that's fine, I'll delve into the source code.
cheers,
Cameron Smith
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