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Matt Sergeant


XML::XPath::XMLParser - The default XML parsing class that produces a node tree


    my $parser = XML::XPath::XMLParser->new(
                filename => $self->get_filename,
                xml => $self->get_xml,
                ioref => $self->get_ioref,
                parser => $self->get_parser,
    my $root_node = $parser->parse;


This module generates a node tree for use as the context node for XPath processing. It aims to be a quick parser, nothing fancy, and yet has to store more information than most parsers. To achieve this I've used array refs everywhere - no hashes. I don't have any performance figures for the speedups achieved, so I make no appologies for anyone not used to using arrays instead of hashes. I think they make good sense here where we know the attributes of each type of node.

Node Structure

All nodes have the same first 2 entries in the array: node_parent and node_pos. The type of the node is determined using the ref() function. The node_parent always contains an entry for the parent of the current node - except for the root node which has undef in there. And node_pos is the position of this node in the array that it is in (think: $node == $node->[node_parent]->[node_children]->[$node->[node_pos]] )

Nodes are structured as follows:

Root Node

The root node is just an element node with no parent.

      undef, # node_parent - check for undef to identify root node
      undef, # node_pos
      undef, # node_prefix
      [ ... ], # node_children (see below)

Element Node

      $parent, # node_parent
      <position in current array>, # node_pos
      'xxx', # node_prefix - namespace prefix on this element
      [ ... ], # node_children
      'yyy', # node_name - element tag name
      [ ... ], # node_attribs - attributes on this element
      [ ... ], # node_namespaces - namespaces currently in scope

Attribute Node

      $parent, # node_parent - the element node
      <position in current array>, # node_pos
      'xxx', # node_prefix - namespace prefix on this element
      'href', # node_key - attribute name
      'ftp://ftp.com/', # node_value - value in the node

Namespace Nodes

Each element has an associated set of namespace nodes that are currently in scope. Each namespace node stores a prefix and the expanded name (retrieved from the xmlns:prefix="..." attribute).

      'a', # node_prefix - the namespace as it was written as a prefix
      'http://my.namespace.com', # node_expanded - the expanded name.

Text Nodes

      'This is some text' # node_text - the text in the node

Comment Nodes

      'This is a comment' # node_comment

Processing Instruction Nodes

      'target', # node_target
      'data', # node_data


If you feel the need to use this module outside of XML::XPath (for example you might use this module directly so that you can cache parsed trees), you can follow the following API:


The new method takes either no parameters, or any of the following parameters:


This uses the familiar hash syntax, so an example might be:

    use XML::XPath::XMLParser;
    my $parser = XML::XPath::XMLParser->new(filename => 'example.xml');

The parameters represent a filename, a string containing XML, an XML::Parser instance and an open filehandle ref respectively. You can also set or get all of these properties using the get_ and set_ functions that have the same name as the property: e.g. get_filename, set_ioref, etc.


The parse method generally takes no parameters, however you are free to pass either an open filehandle reference or an XML string if you so require. The return value is a tree that XML::XPath can use. The parse method will die if there is an error in your XML, so be sure to use perl's exception handling mechanism (eval{};) if you want to avoid this.


The parsefile method is identical to parse() except it expects a single parameter that is a string naming a file to open and parse. Again it returns a tree and also dies if there are XML errors.


This file is distributed as part of the XML::XPath module, and is copyright 2000 Fastnet Software Ltd. Please see the documentation for the module as a whole for licencing information.