XML::XPathEngine(3) User Contributed Perl Documentation 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
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
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
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 ;--)
WARNING: 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, $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, $context)
Returns the nodes found as a single string. The result is not guaranteed to be valid XML
though (it could for example be just text if the query returns attribute values).
findnodes_as_strings ($path, $context)
Returns the nodes found as a list of strings, one per node found.
findvalue ($path, $context)
Returns the result as a string (the concatenation of the values of the result nodes).
Returns the values of the result nodes as a list of strings.
exists ($path, $context)
Returns true if the given path exists.
matches($node, $path, $context)
Returns true if the node matches the path.
find ($path, $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 $nodeset->size. See XML::XPathEngine::NodeSet.
Returns the text string for a particular node. Returns a string, or undef if the node
set_namespace ($prefix, $uri)
Sets the namespace prefix mapping to the uri.
Normally in XML::XPathEngine the prefixes in XPath node tests take their context from the
current node. This means that foo:bar will always match an element <foo:bar> regardless of
the namespace that the prefix foo is mapped to (which might even change within the
document, resulting in unexpected results). In order to make prefixes in XPath node tests
actually map to a real URI, you need to enable that via a call to the set_namespace method
of your XML::XPathEngine object.
Clears all previously set namespace mappings.
get_namespace ($prefix, $node)
Returns the uri associated to the prefix for the node (mostly for internal usage)
By default, for historical as well as convenience reasons, XML::XPathEngine has a slightly
non-standard way of dealing with the default namespace.
If you search for "//tag" it will return elements "tag". As far as I understand it, if the
document has a default namespace, this should not return anything. You would have to
first do a "set_namespace", and then search using the namespace.
Passing a true value to "set_strict_namespaces" will activate this behaviour, passing a
false value will return it to its default behaviour.
set_var ($var. $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 don't want namespace processing to occur. This will make everything a
little (tiny) bit faster, but you'll suffer for it, probably.
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,
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
Please report any bugs or feature requests to "email@example.com", or
through the web interface at
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=XML-XPathEngine>. I will be notified, and
then you'll 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
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
perl v5.16.3 2013-05-13 XML::XPathEngine(3)