NAME
   "Config::XPath" - retrieve configuration data from XML files by using
   XPath

SYNOPSIS
    use Config::XPath;

    my $conf = Config::XPath->new( filename => 'addressbook.xml' );

    ## Basic data retrieval

    my $bob_phone = $conf->get_string( '//user[@name="bob"]/@phone' );

    my %jim_details = $conf->get_attrs( '//user[@name="jim"]' );

    my @everyone_with_fax = $conf->get_list( '//user[@fax]' );
    print " $_ has a fax\n" for @everyone_with_fax;

    my $phone_map = $conf->get_map( '//user', '@name', '@phone' );
    print " $_ has a phone: $phone_map->{$_}\n" for sort keys %$phone_map;

    ## Subconfigurations

    my $james_config = $conf->get_sub( '//user[@name="james"]' );
    my $james_phone = $james_config->get_string( '@phone' );

    foreach my $user_config ( $conf->get_sub_list( '//user[@email]' ) ) {
       my $town = $user_config->get_string( 'address/town' );
       print "Someone in $town has an email account\n";
    }

DESCRIPTION
   This module provides easy access to configuration data stored in an XML
   file. Configuration is retrieved using XPath keys; various methods exist
   to convert the result to a variety of convenient forms.

   If the methods are called as static functions (as opposed to as object
   methods) then they access data stored in the default configuration file
   (details given below).

 Subconfigurations
   By default, the XPath context is at the root node of the XML document.
   If some other context is required, then a subconfiguration object can be
   used. This is a child "Config::XPath" object, built from an XPath query
   on the parent. Whatever node the query matches becomes the context for
   the new object. The methods "get_sub()" and "get_sub_list()" perform
   this task; the former returning a single child, and the latter returning
   a list of all matches.

CONSTRUCTOR
 $conf = Config::XPath->new( %args )
   This function returns a new instance of a "Config::XPath" object,
   containing the configuration in the named XML file. If the given file
   does not exist, or an error occured while reading it, an exception is
   thrown.

   The %args hash requires one the following keys to provide the XML
   source:

   filename => $file
           The filename of the XML file to read

   xml => $xml
           A string containing XML data

   ioref => IO
           An IO handle reference

   Also may be provided:

   parser => $parser
           An "XML::Parser" object

   If a parser is not provided, one will be constructed internally.

METHODS
 $result = $config->get( $paths, %args )
   This method retrieves the result of one of more XPath expressions from
   the XML file. Each expression should give either a text-valued element
   with no sub-elements, an attribute, or an XPath function that returns a
   string, integer or boolean value.

   The $paths argument should contain a data tree of ARRAY and HASH
   references, whose leaves will be the XPath expressions used. The $result
   will be returned in a similar tree structure, with the leaves containing
   the value each expression yielded against the XML config. The %args may
   contain a "default" key, which should give default values for these
   results, also in a similar tree structure.

   If no suitable node was found matching an XPath expression and no
   corresponding "default" value is found, then an exception is thrown. If
   more than one node is returned, or the returned node is not either a
   plain-text content containing no child nodes, or an attribute, then an
   exception is thrown.

   $paths  A tree data structure containing ARRAY and HASH references, and
           XPath expressions stored in plain scalars.

   %args   A hash that may contain extra options to control the operation.
           Supports the following keys:

           "default"
               Contains a tree in the same structure as the $paths, whose
               leaf values should be returned instead of the value yielded
               by the XPath expression, in the case that no nodes match it.

 $str = $config->get_string( $path, %args )
   This function is a smaller version of the "get" method, which only works
   on a single string path.

   $path   The XPath to the required configuration node

   %args   A hash that may contain extra options to control the operation.
           Supports the following keys:

           "default"
               If no XML node is found matching the path, return this value
               rather than throwing an exception.

 $attrs = $config->get_attrs( $path )
   This method retrieves the attributes of a single element in the XML
   file. The attributes are returned in a hash, along with the name of the
   element itself, which is returned in a special key named '+'. This name
   is not valid for an XML attribute, so this key will never clash with an
   actual value from the XML file.

   If no suitable node was found matching the XPath query, then an
   exception is thrown. If more than one node matched, or the returned node
   is not an element, then an exception is thrown.

   "*$path*"
           The XPath to the required configuration node

 @results = $config->get_list( $listpath; $valuepaths, %args )
   This method obtains a list of nodes matching the $listpath expression.
   For each node in the list, it obtains the result of the $valuepaths with
   the XPath context at each node, and returns them all in a list. The
   $valuepaths argument can be a single string expression, or an ARRAY or
   HASH tree, as for the "get()" method.

   If the $valuepaths argument is not supplied, the type of each node
   determines the value that will be returned. Element nodes return a
   hashref, identical to that which "get_attrs()" returns. Other nodes will
   return their XPath string value.

   $listpath
           The XPath expression to generate the list of nodes.

   $valuepaths
           Optional. If present, the XPath expression or tree of
           expressions to generate the results.

   %args   A hash that may contain extra options to control the operation.
           Supports the following keys:

           "default"
               Contains a tree in the same structure as the $valuepaths,
               whose leaf values should be returned instead of the value
               yielded by the XPath expression, in the case that no nodes
               match it.

 $map = $config->get_map( $listpath, $keypath, $valuepaths, %args )
   This method obtains a map, returned as a hash, containing one entry for
   each node returned by the $listpath search, where the key and value are
   given by the $keypath and $valuepaths within each node. It is not an
   error for no nodes to match the $listpath.

   The result of the $listpath query must be a nodeset. The result of the
   $keypath is used as the hash key for each node, and must be convertable
   to a string, by the same rules as the "get_string()" method. The value
   for each node in the hash will be obtained using the $valuepaths, which
   can be a plain string, or an ARRAY or HASH tree, as for the "get()"
   method.

   The keys obtained by the $keypath should be unique. In the case of
   duplicates, the last value from the nodeset is used.

   $listpath
           The XPath to generate the nodeset

   $keypath
           The XPath within each node to generate the key

   $valuepaths
           The XPath expression or tree of expressions within each node to
           generate the value.

   %args   A hash that may contain extra options to control the operation.
           Supports the following keys:

           "default"
               Contains a tree in the same structure as the $valuepaths,
               whose leaf values should be returned instead of the value
               yielded by the XPath expression, in the case that no nodes
               match it.

 $subconfig = $config->get_sub( $path )
   This method constructs a new "Config::XPath" object whose context is at
   the single node selected by the XPath query. The newly constructed child
   object is then returned.

   If no suitable node was found matching the XPath query, then an
   exception of is thrown. If more than one node matched, then an exception
   is thrown.

   $path   The XPath to the required configuration node

 @subconfigs = $config->get_sub_list( $path )
   This method constructs a list of new "Config::XPath" objects whose
   context is at each node selected by the XPath query. The array of newly
   constructed objects is then returned. Unlike other methods, it is not an
   error for no nodes to match.

   $path   The XPath for the required configuration

DEFAULT CONFIG FILE
   In the case of calling as static functions, the default configuration is
   accessed. When the module is loaded no default configuration exists, but
   one can be loaded by calling the "read_default_config()" function. This
   makes programs simpler to write in cases where only one configuration
   file is used by the program.

 read_default_config( $file )
   This function reads the default configuration file, from the location
   given. If the file is not found, or an error occurs while reading it,
   then an exception is thrown.

   The default configuration is cached, so multiple calls to this function
   will not result in multiple reads of the file; subsequent requests will
   be silently ignored, even if a different filename is given.

   $file   The filename of the default configuration to load

FUNCTIONS
   Each of the following functions is equivalent to a similar method called
   on the default configuration, as loaded by "read_default_config()".

 $str = get_config_string( $path, %args )
   Equivalent to the "get_string()" method

 $attrs = get_config_attrs( $path )
   Equivalent to the "get_attrs()" method

 @values = get_config_list( $path )
   Equivalent to the "get_list()" method

 $map = get_config_map( $listpath, $keypath, $valuepath )
   Equivalent to the "get_map()" method

 $map = get_sub_config( $path )
   Equivalent to the "get_sub()" method

 $map = get_sub_config_list( $path )
   Equivalent to the "get_sub_list()" method

SEE ALSO
   *   XML::XPath - Perl XML module that implements XPath queries

AUTHOR
   Paul Evans <[email protected]>

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