Config::XPath - a module for retrieving configuration data from XML files
by using XPath queries
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"; }
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).
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.
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 Config::XPath::Exception
is thrown.
The %args hash takes the following keys:
The filename of the XML file to read
A string containing XML data
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 of
Config::XPath::ConfigNotFoundException class 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 of class
Config::XPath::BadConfigException class is thrown.
A tree data structure containing ARRAY and HASH references, and XPath expressions stored in plain scalars.
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.
This function is a smaller version of the get method, which only works on a
single string path.
The XPath to the required configuration node
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 a Config::XPath::ConfigNotFoundException.
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 of
Config::XPath::ConfigNotFoundException class is thrown. If more than one
node matched, or the returned node is not an element, then an exception of
class Config::XPath::BadConfigException class is thrown.
$path
The XPath to the required configuration node
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.
The XPath expression to generate the list of nodes.
Optional. If present, the XPath expression or tree of expressions to generate the results.
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.
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.
The XPath to generate the nodeset
The XPath within each node to generate the key
The XPath expression or tree of expressions within each node to generate the value.
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.
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
Config::XPath::ConfigNotFoundException class is thrown. If more than one
node matched, then an exception of class Config::XPath::BadConfigException
is thrown.
The XPath to the required configuration node
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.
The XPath for the required configuration
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.
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 of Config::XPath::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.
The filename of the default configuration to load
Each of the following functions is equivalent to a similar method called on
the default configuration, as loaded by read_default_config().
Equivalent to the get_string() method
Equivalent to the get_attrs() method
Equivalent to the get_list() method
Equivalent to the get_map() method
Equivalent to the get_sub() method
Equivalent to the get_sub_list() method
This exception is used as a base class for config-related exceptions. It is
derived from Error, and stores the config path involved.
$e = Config::XPath::Exception->new( $message; $path )
The path is optional, and will only be stored if defined. It can be accessed
using the path method.
$path = $e->path
This exception indicates that the requested configuration was not found. It is
derived from Config::XPath::Exception and is constructed and accessed in
the same way.
This exception indicates that configuration found at the requested path was
not of a type suitable for the request made. It is derived from
Config::XPath::Exception and is constructed and accessed in the same way.
This exception indicates that no default configuration has yet been loaded
when one of the accessor functions is called directly. It is derived from
Config::XPath::Exception.
$e = Config::XPath::NoDefaultConfigException->new( $path )
the XML::XPath manpage - Perl XML module that implements XPath queries
the Error manpage - Base module for exception-based error handling
Paul Evans <leonerd@leonerd.org.uk>