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Connector(3)	      User Contributed Perl Documentation	  Connector(3)

NAME
       Connector - a generic connection	to a hierarchical-structured data set

DESCRIPTION
       The Connector is	generic	connection to a	data set, typically
       configuration data in a hierarchical structure. Each connector object
       accepts the get(KEY) method, which, when	given a	key, returns the
       associated value	from the connector's data source.

       Typically, a connector acts as a	proxy to a simple data source like
       YAML, Config::Std, Config::Versioned, or	to a more complex data source
       like an LDAP server or Proc::SafeExec. The standard calling convention
       via get(KEY) makes the connectors interchangeable.

       In addition, a set of meta-connectors may be used to combine multiple
       connectors into more complex chains. The	Connector::Multi, for example,
       allows for redirection to delegate connectors via symbolic links. If
       you have	a list of connectors and want to use them in a load-balancing,
       round-robin fashion or have the list iterated until a value is found,
       use Connector::List and choose the algorithm to perform.

SYNOPSIS
	   use Connector::MODULENAME;

	   my $conn = Connector::MODULENAME->new( {
	       LOCATION	=> $path_to_config_for_module,
	   });

	   my $val = $conn->get('full.name.of.key');

   Connector Class
       This is the base	class for all Connector	implementations. It provides
       common helper methods and performs common sanity	checking.

       Usually this class should not be	instantiated directly.

CONFIGURATION
   die_on_undef
       Set to true if you want the connector to	die when a query reaches a
       non-exisiting node. This	will affect calls to get/get_list/get_hash and
       will not	affect values that are explicitly set to undef (if supported
       by the connector!).

       Each accessor method is valid only on special types of nodes. If	you
       call them on a wrong type of node, the connector	may retunr unexpected
       result or simply	die.

   exists
   get
       Basic method to obtain a	scalar value at	the leaf of the	config tree.

	 my $value = $connector->get('smartcard.owners.tokenid.bob');

       Each implementation must	also accept an arrayref	as path. The path is
       contructed from the elements. The default behaviour allows strings
       using the delimiter character inside an array element. If you want each
       array element to	be parsed, you need to pass "RECURSEPATH => 1" to the
       constructor.

	 my $value = $connector->get( [	'smartcard','owners','tokenid','bob.builder' ] );

       Some implementations accept control parameters, which can be passed by
       params, which is	a hash ref of key => value pairs.

	 my $value = $connector->get( 'smartcard.owners.tokenid.bob' , { version => 1 }	);

   get_list
       This method is only valid if it is called on a "n-1" depth node
       representing an ordered list of items (array). The return value is an
       array with all values present below the node.

	 my @items = $connector->get_list( 'smartcard.owners.tokenid'  );

   get_size
       This method is only valid if it is called on a "n-1" depth node
       representing an ordered list of items (array). The return value is the
       number of elements in this array	(including undef elements if they are
       explicitly given).

	 my $count = $connector->get_size( 'smartcard.owners.tokens.bob' );

       If the node does	not exist, 0 is	returned.

   get_hash
       This method is only valid if it is called on a "n-1" depth node
       representing a key => value list	(hash).	The return value is a hash
       ref.

	 my %data = %{$connector->get_hash( 'smartcard.owners.tokens.bob' )};

   get_keys
       This method is only valid if it is called on a "n-1" depth node
       representing a key => value list	(hash).	The return value is an array
       holding the values of all keys (including undef elements	if they	are
       explicitly given).

	 my @keys = $connector->get_keys( 'smartcard.owners.tokens.bob'	);

       If the node does	not exist, an empty list is returned.

   get_reference
       Rarely used, returns the	value of a reference node. Currently used by
       Connector::Multi	in combination with
       Connector::Proxy::Config::Versioned to create internal links and
       cascaded	connectors. See	Connector::Multi for details.

   set
       The set method is a "all	in one"	implementation,	that is	used for
       either type of value. If	the value is not a scalar, it must be passed
       by reference.

	 $connector->set('smartcard.owners.tokenid.bob', $value, $params);

       The value parameter holds a scalar or ref to an array/hash with the
       data to be written. params is a hash ref	which holds additional
       parameters for the operation and	can be undef if	not needed.

STRUCTURAL METHODS
   get_meta
       This method returns some	structural information about the current node
       as hash ref. At minimum it must return the type of node at the current
       path.

       Valid values are	scalar,	list, hash, reference. The types match the
       accessor	methods	given above (use "get" for scalar).

	   my $meta = $connector->get_meta( 'smartcard.owners' );
	   my $type = $meta->{TYPE};

       When you	call a proxy connector without sufficient arguments to perform
       the query, you will receive a value of connector	for type. Running a
       get_* method against such a node	will cause the connector to die!

IMPLEMENTATION GUIDELINES
       You SHOULD use the _node_not_exists method if the requested path	does
       not exist or has	an undefined value. This will internally take care of
       the die_on_undef	setting	and throw an exception or return undef.	So you
       can just	write:

	   if (path not	exists || not defined val) {
	       return $self->_node_not_exists( pathspec	);
	   }

   path	building
       You should always pass the first	parameter to the private "_build_path"
       method. This method converts any	valid path spec	representation to a
       valid path. It takes care of the	RECURSEPATH setting and	returns	the
       path elements as	list.

   Supported methods
       The methods get,	get_list, get_size, get_hash, get_keys,	set, get_meta
       are routed to the appropriate connector.

       You MUST	implement at minimum one of the	three data getters, if
       get_list/get_keys is omited, the	base class will	do a get_list/get_keys
       call and	return the info	which will be a	correct	result but might be
       expensive, so you can provide your own implementiation if required.

       You MUST	also implement the get_meta method. If you have	a connector
       with a fixed type, you MAY check	if the particular path exists and
       return the result of _node_not_exists.

AUTHORS
       Scott Hardin <mrscotty@cpan.org>

       Martin Bartosch

       Oliver Welter

COPYRIGHT
       Copyright 2013 OpenXPKI Foundation

       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

POD ERRORS
       Hey! The	above document had some	coding errors, which are explained
       below:

       Around line 360:
	   Unknown directive: =head

perl v5.24.1			  2016-12-13			  Connector(3)

NAME | DESCRIPTION | SYNOPSIS | CONFIGURATION | STRUCTURAL METHODS | IMPLEMENTATION GUIDELINES | AUTHORS | COPYRIGHT | POD ERRORS

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