phpman > perldoc > XML::XPath

NAME
    XML::XPath - Parse and evaluate XPath statements.

VERSION
    Version 1.44

DESCRIPTION
    This module aims to comply exactly to the XPath specification at http://www.w3.org/TR/xpath and
    yet allow extensions to be added in the form of functions.Modules such as XSLT and XPointer may
    need to do this as they support functionality beyond XPath.

SYNOPSIS
        use XML::XPath;
        use XML::XPath::XMLParser;

        my $xp = XML::XPath->new(filename => 'test.xhtml');

        my $nodeset = $xp->find('/html/body/p'); # find all paragraphs

        foreach my $node ($nodeset->get_nodelist) {
            print "FOUND\n\n",
                XML::XPath::XMLParser::as_string($node),
                "\n\n";
        }

DETAILS
    There is an awful lot to all of this, so bear with it - if you stick it out it should be worth
    it. Please get a good understanding of XPath by reading the spec before asking me questions. All
    of the classes and parts herein are named to be synonymous with the names in the specification,
    so consult that if you don't understand why I'm doing something in the code.

METHODS
    The API of XML::XPath itself is extremely simple to allow you to get going almost immediately.
    The deeper API's are more complex, but you shouldn't have to touch most of that.

  new()
    This constructor follows the often seen named parameter method call. Parameters you can use are:
    filename, parser, xml, ioref and context. The filename parameter specifies an XML file to parse.
    The xml parameter specifies a string to parse, and the ioref parameter specifies an ioref to
    parse. The context option allows you to specify a context node. The context node has to be in
    the format of a node as specified in XML::XPath::XMLParser. The 4 parameters filename, xml,
    ioref and context are mutually exclusive - you should only specify one (if you specify anything
    other than context, the context node is the root of your document). The parser option allows you
    to pass in an already prepared XML::Parser object, to save you having to create more than one in
    your application (if, for example, you are doing more than just XPath).

        my $xp = XML::XPath->new( context => $node );

    It is very much recommended that you use only 1 XPath object throughout the life of your
    application. This is because the object (and it's sub-objects) maintain certain bits of state
    information that will be useful (such as XPath variables) to later calls to find(). It's also a
    good idea because you'll use less memory this way.

  find($path, [$context])
    The find function takes an XPath expression (a string) and returns either an XML::XPath::NodeSet
    object containing the nodes it found (or empty if no nodes matched the path), or one of
    XML::XPath::Literal (a string), XML::XPath::Number or XML::XPath::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::XPath::NodeSet. An optional
    second parameter of a context node allows you to use this method repeatedly, for example XSLT
    needs to do this.

  findnodes($path, [$context])
    Returns a list of nodes found by $path, optionally in context $context. In scalar context
    returns an XML::XPath::NodeSet object.

  matches($node, $path, [$context])
    Returns true if the node matches the path (optionally in context $context).

  findnodes_as_string($path, [$context])
    Returns the nodes found reproduced as XML.The result isn't guaranteed to be valid XML though.

  findvalue($path, [$context])
    Returns either a "XML::XPath::Literal", a "XML::XPath::Boolean" or a "XML::XPath::Number"
    object.If the path returns a NodeSet,$nodeset->to_literal is called automatically for you (and
    thus a "XML::XPath::Literal" is returned).Note that for each of the objects stringification is
    overloaded, so you can just print the value found, or manipulate it in the ways you would a
    normal perl value (e.g. using regular expressions).

  exists($path, [$context])
    Returns true if the given path exists.

  getNodeText($path)
    Returns the XML::XPath::Literal for a particular XML node. Returns a string if exists or ''
    (empty string) if the node doesn't exist.

  setNodeText($path, $text)
    Sets the text string for a particular XML node. The node can be an element or an attribute. If
    the node to be set is an attribute, and the attribute node does not exist, it will be created
    automatically.

  createNode($path)
    Creates the node matching the $path given. If part of the path given or all of the path do not
    exist, the necessary nodes will be created automatically.

  set_namespace($prefix, $uri)
    Sets the namespace prefix mapping to the uri.

    Normally in "XML::XPath" the prefixes in XPath node test 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::XPath" object.

  clear_namespaces()
    Clears all previously set namespace mappings.

  $XML::XPath::Namespaces
    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
    See XML::XPath::Node, XML::XPath::Node::Element, XML::XPath::Node::Text,
    XML::XPath::Node::Comment, XML::XPath::Node::Attribute, XML::XPath::Node::Namespace, and
    XML::XPath::Node::PI.

On Garbage Collection
    XPath nodes work in a special way that allows circular references, and yet still lets Perl's
    reference counting garbage collector to clean up the nodes after use. This should be totally
    transparent to the user, with one caveat: If you free your tree before letting go of a
    sub-tree,consider that playing with fire and you may get burned. What does this mean to the
    average user? Not much. Provided you don't free (or let go out of scope) either the tree you
    passed to XML::XPath->new, or if you didn't pass a tree, and passed a filename or IO-ref, then
    provided you don't let the XML::XPath object go out of scope before you let results of find()
    and its friends go out of scope, then you'll be fine. Even if you do let the tree go out of
    scope before results, you'll probably still be fine. The only case where you may get stung is
    when the last part of your path/query is either an ancestor or parent axis. In that case the
    worst that will happen is you'll end up with a circular reference that won't get cleared until
    interpreter destruction time.You can get around that by explicitly calling $node->DESTROY on
    each of your result nodes, if you really need to do that.

    Mail me direct if that's not clear. Note that it's not doom and gloom. It's by no means
    perfect,but the worst that will happen is a long running process could leak memory. Most long
    running processes will therefore be able to explicitly be careful not to free the tree (or
    XML::XPath object) before freeing results.AxKit, an application that uses XML::XPath, does this
    and I didn't have to make any changes to the code - it's already sensible programming.

    If you *really* don't want all this to happen, then set the variable $XML::XPath::SafeMode, and
    call $xp->cleanup() on the XML::XPath object when you're finished, or $tree->dispose() if you
    have a tree instead.

Example
    Please see the test files in t/ for examples on how to use XPath.

AUTHOR
    Original author Matt Sergeant, "<matt at sergeant.org>"

    Currently maintained by Mohammad S Anwar, "<mohammad.anwar at yahoo.com>"

SEE ALSO
    XML::XPath::Literal, XML::XPath::Boolean, XML::XPath::Number, XML::XPath::XMLParser,
    XML::XPath::NodeSet, XML::XPath::PerlSAX, XML::XPath::Builder.

LICENSE AND COPYRIGHT
    This module is copyright 2000 AxKit.com Ltd. This is free software, and as such comes with NO
    WARRANTY. No dates are used in this module. You may distribute this module under the terms of
    either the Gnu GPL, or the Artistic License (the same terms as Perl itself).

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