Manual Reference Pages - XML::XPATHENGINE (3)
XML::XPathEngine - a re-usable XPath engine for DOM-like trees
This module provides an XPath engine, that can be re-used by other
module/classes that implement trees.
In order to use the XPath engine, nodes in the user module need to mimick
DOM nodes. The degree of similitude between the user tree and a DOM dictates
how much of the XPath features can be used. A module implementing all of the
DOM should be able to use this module very easily (you might need to add
the cmp method on nodes in order to get ordered result sets).
This code is a more or less direct copy of the XML::XPath module by
Matt Sergeant. I only removed the XML processing part to remove the dependency
on XML::Parser, applied a couple of patches, renamed a whole lot of methods
to make Pod::Coverage happy, and changed the docs.
The article eXtending XML XPath, http://www.xmltwig.com/article/extending_xml_xpath/
should give authors who want to use this module enough background to do so.
Otherwise, my email is below ;--)
<B>WARNINGB>: while the underlying code is rather solid, this module mostly lacks docs.
As they say, patches welcome...
my $tree= my_tree->new( ...);
my $xp = XML::XPathEngine->new();
my @nodeset = $xp->find(/root/kid/grandkid, $tree); # find all first grankids
# needs to provide DOM methods
XML::XPathEngine will provide the following methods:
findnodes ($path, CW$context)
Returns a list of nodes found by $path, optionally in context $context.
In scalar context returns an XML::XPathEngine::NodeSet object.
findnodes_as_string ($path, CW$context)
Returns the nodes found as a single string. The result is
not guaranteed to be valid XML though (it could for example be just text
if the query returns attribute values).
findnodes_as_strings ($path, CW$context)
Returns the nodes found as a list of strings, one per node found.
findvalue ($path, CW$context)
Returns the result as a string (the concatenation of the values of the
Returns the values of the result nodes as a list of strings.
exists ($path, CW$context)
Returns true if the given path exists.
matches($node, CW$path, CW$context)
Returns true if the node matches the path.
find ($path, CW$context)
The find function takes an XPath expression (a string) and returns either a
XML::XPathEngine::NodeSet object containing the nodes it found (or empty if
no nodes matched the path), or one of XML::XPathEngine::Literal (a string),
XML::XPathEngine::Number, or XML::XPathEngine::Boolean. It should always return
something - and you can use ->isa() to find out what it returned. If you
need to check how many nodes it found you should check $nodeset->size.
Returns the text string for a particular node. Returns a string,
or undef if the node doesnt exist.
set_namespace ($prefix, CW$uri)
Sets the namespace prefix mapping to the uri.
Normally in XML::XPathEngine the prefixes in XPath node tests take their
context from the current node. This means that foo:bar will always
match an element <foo:bar> regardless of the namespace that the prefix
foo is mapped to (which might even change within the document, resulting
in unexpected results). In order to make prefixes in XPath node tests
actually map to a real URI, you need to enable that via a call
to the set_namespace method of your XML::XPathEngine object.
Clears all previously set namespace mappings.
get_namespace ($prefix, CW$node)
Returns the uri associated to the prefix for the node (mostly for internal usage)
By default, for historical as well as convenience reasons, XML::XPathEngine
has a slightly non-standard way of dealing with the default namespace.
If you search for //tag it will return elements tag. As far as I understand it,
if the document has a default namespace, this should not return anything.
You would have to first do a set_namespace, and then search using the namespace.
Passing a true value to set_strict_namespaces will activate this behaviour, passing a
false value will return it to its default behaviour.
set_var ($var. CW$val)
Sets an XPath variable (that can be used in queries as $var)
Returns the value of the XPath variable (mostly for internal usage)
Set this to 0 if you dont want namespace processing to occur. This
will make everything a little (tiny) bit faster, but youll suffer for it,
Node Object Model
Nodes need to provide the same API as nodes in XML::XPath (at least the access
API, not the tree manipulation one).
Please see the test files in t/ for examples on how to use XPath.
The module supports the XPath recommendation to the same extend as XML::XPath
(that is, rather completely).
It includes a perl-specific extension: direct support for regular expressions.
You can use the usual (in Perl!) =~ and !~ operators. Regular expressions
are / delimited (no other delimiter is accepted, \ inside regexp must be
backslashed), the imsx modifiers can be used.
$xp->findnodes( //@att[.=~ /^v.$/]); # returns the list of attributes att
# whose value matches ^v.$
HTML::TreeBuilder::XPath, XML::Twig::XPath for exemples of using this module
Tree::XPathEngine for a similar module for non-XML trees.
<http://www.xmltwig.com/article/extending_xml_xpath/> for background
information. The last section of the article summarizes how to reuse XML::XPath.
As XML::XPathEngine offers the same API it should help you
Michel Rodriguez, <firstname.lastname@example.org>
Most code comes directly from XML::XPath, by Matt Sergeant.
Please report any bugs or feature requests to
email@example.com, or through the web interface at
I will be notified, and then youll automatically be notified of progress on
your bug as I make changes.
COPYRIGHT & LICENSE
XML::XPath Copyright 2000 AxKit.com Ltd.
Copyright 2006 Michel Rodriguez, All Rights Reserved.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
|perl v5.20.3 ||XML::XPATHENGINE (3) ||2016-03-17 |
Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.