On 04/25/2014 12:42 PM, Matt Benson wrote:
Pointer is an interface that is considered part of the public API.
Very possibly the intent could have been more elegantly expressed by
using the NodePointer API, but this *would* be a case of relying on an
implementation detail, as NodePointer is the Pointer implementation
used by JXPathContextReferenceImpl.
Okay, so I need to read the docs more thoroughly. :)
Thanks for the help!
Matt
On Fri, Apr 25, 2014 at 12:39 PM, John Casey <[email protected]
<mailto:[email protected]>> wrote:
Yep, that makes a certain kind of sense, though I guess I wouldn't
exactly call it intuitive. I can see how creating a new context
each time could be a bad idea (and very inefficient, I
suspect)...though it seems (to a newbie anyway) that the pointers
are an implementation detail that leak out in this case.
Or, maybe I just haven't read enough of the docs?
At any rate, thanks for your reply. Maybe once this project I'm
working on is done, I'll take a look at modernizing JXPath. It
does seem faster than the built-in JAXP stuff.
-john
On 04/25/2014 12:33 PM, Matt Benson wrote:
Hi, John. Sorry for the long delay.
The original authors of JXPath are long gone, but from what I
can reconstruct the intent of nested JXPathContexts is only to
unify treatment of things like variables, namespaces, and at a
guess, functions. AFAICT your test case appears to have
overcomplicated the issue, although notably my alternative does
resort to some string concatentation to accomplish the same
apparent purpose of the test case. Certainly the whole JXPath
codebase could benefit from some modernization. In any event, I have:
@Test
public void anotherTest() throws Exception {
final InputStream is =
Thread.currentThread().getContextClassLoader().getResourceAsStream("jxpath/simple.pom.xml");
final Document document =
DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(is);
final JXPathContext ctx = JXPathContext.newContext(document);
// not sure why this was done, but I have preserved it
document.getDocumentElement().removeAttribute("xmlns");
for (@SuppressWarnings("unchecked")
Iterator<Pointer> ptrs =
ctx.iteratePointers("/project/dependencies/dependency");
ptrs.hasNext();) {
final Pointer ptr = ptrs.next();
dump((Node) ptr.getNode());
System.out.printf("declared by project with groupId
'%s'%n", ctx.getValue(ptr.asPath() + "/ancestor::project/groupId"));
}
}
which yields output:
<dependency>
<groupId>org.group</groupId>
<artifactId>artifact-id</artifactId>
<version>2.6</version>
</dependency>
declared by project with groupId 'org.test'
Does this help?
Matt
On Mon, Apr 14, 2014 at 1:09 PM, John Casey <[email protected]
<mailto:[email protected]>> wrote:
Hi all,
I'm trying to learn how to use JXPath with DOM in order to
speed up some code that uses a lot of xpath. I've seen blog
posts suggesting it's about twice as fast as JAXP's XPath
processor...
The problem I'm running into is when I construct a
JXPathContext around a node down in the DOM tree, then try to
select a node elsewhere in the tree using the ancestor::
axis. I'm attaching a sample XML file and unit test that
shows what I'm trying to do.
I've run this through a debugger, and it appears that the
DOMNodePointer.getImmediateParent() doesn't even try to look
at the Node.getParentNode()...if it doesn't have a
pre-existing parent (from its ctor) then it just dumbly
returns the null parent.
I haven't done enough research yet to know how to get
DOMNodePointer to populate its parent (using the public API,
not the nuts-and-bolts impl details), but in the attached
example you can see I try two approaches:
1. the naive approach, which is also the last one in the
code. IMO, this one should work!
2. a brute-force alternative, where JXPathContext instances
for each intermediate node are created to inherit in the
right order, all the way back to the document itself. From my
partial reading of the code, this should work even if the
naive approach doesn't.
Neither of these works, though. Can someone shed some light
on it, or let me know if I've found a bug (seems like a
common use case)...
Thanks,
-john
--
John Casey
GitHub - http://github.com/jdcasey
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