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CGI::Session::Driver(3pm) User Contributed Perl Documentation CGI::Session::Driver(3pm)
NAME
CGI::Session::Driver - CGI::Session driver specifications
SYNOPSIS
require CGI::Session::Driver;
@ISA = qw( CGI::Session::Driver );
DESCRIPTION
CGI::Session::Driver is a base class for all CGI::Session's native drivers. It also
documents driver specifications for those willing to write drivers for different databases
not currently supported by CGI::Session.
WHAT IS A DRIVER
Driver is a piece of code that helps CGI::Session library to talk to specific database
engines, or storage mechanisms. To be more precise, driver is a .pm file that inherits
from CGI::Session::Driver and defines retrieve(), store() and remove() methods.
BLUEPRINT
The best way of learning the specs is to look at a blueprint of a driver:
package CGI::Session::Driver::your_driver_name;
use strict;
use base qw( CGI::Session::Driver CGI::Session::ErrorHandler );
sub init {
my ($self) = @_;
# optional
}
sub DESTROY {
my ($self) = @_;
# optional
}
sub store {
my ($self, $sid, $datastr) = @_;
# Store $datastr, which is an already serialized string of data.
}
sub retrieve {
my ($self, $sid) = @_;
# Return $datastr, which was previously stored using above store() method.
# Return $datastr if $sid was found. Return 0 or "" if $sid doesn't exist
}
sub remove {
my ($self, $sid) = @_;
# Remove storage associated with $sid. Return any true value indicating success,
# or undef on failure.
}
sub traverse {
my ($self, $coderef) = @_;
# execute $coderef for each session id passing session id as the first and the only
# argument
}
1;
All the attributes passed as the second argument to CGI::Session's new() or load() methods
will automatically be made driver's object attributes. For example, if session object was
initialized as following:
$s = CGI::Session->new("driver:your_driver_name", undef, {Directory=>'/tmp/sessions'});
You can access value of 'Directory' from within your driver like so:
sub store {
my ($self, $sid, $datastr) = @_;
my $dir = $self->{Directory}; # <-- in this example will be '/tmp/sessions'
}
Optionally, you can define "init()" method within your driver to do driver specific global
initialization. "init()" method will be invoked only once during the lifecycle of your
driver, which is the same as the lifecycle of a session object.
For examples of "init()" look into the source code of native CGI::Session drivers.
METHODS
This section lists and describes all driver methods. All the driver methods will receive
driver object ($self) as the first argument. Methods that pertain to an individual session
(such as "retrieve()", "store()" and "remove()") will also receive session id ($sid) as
the second argument.
Following list describes every driver method, including its argument list and what step of
session's life they will be invoked. Understanding this may help driver authors.
retrieve($self, $sid)
Called whenever a specific session is requested either via "CGI::Session->new()" or
"CGI::Session->load()" syntax. Method should try to retrieve data associated with
$sid and return it. In case no data could be retrieved for $sid 0 (zero) or ""
should be returned. undef must be returned only to signal error. Error message should
be set via set_error(), which can be inherited from CGI::Session::ErrorHandler.
Tip: set_error() always returns undef. Use it for your advantage.
store($self, $sid, $datastr)
Called whenever modified session data is to be stored back to disk. This happens
whenever CGI::Session->flush() is called on modified session. Since
CGI::Session->DESTROY() calls flush(), store() gets requested each time session object
is to be terminated.
" store() " is called both to store new sessions and to update already stored
sessions. It's driver author's job to figure out which operation needs to be
performed.
$datastr, which is passed as the third argument to represents already serialized
session data that needs to be saved.
store() can return any true value indicating success or undef on failure. Error
message should be passed to set_error()
remove($self, $sid)
Called whenever session data is to be deleted, which is when CGI::Session->delete() is
called. Should return any true value indicating success, undef on failure. Error
message should be logged in set_error().
traverse($self, \&coderef)
Called only from within CGI::Session->find(). Job of traverse() is to call \&coderef
for every single session stored in disk passing session's id as the first and only
argument: "$coderef->( $sid )"
init($self)
Optional. Called whenever driver object is to be initialized, which happens only once
during the lifecycle of CGI::Session object. Here you can do driver-wide
initialization, such as to open connection to a database server.
DESTROY($self)
Optional. Perl automatically calls this method on objects just before they are to be
terminated. This gives your driver chance to close any database connections or close
any open file handles.
NOTES
o All driver .pm files must be lowercase!
o DBI-related drivers are better off using CGI::Session::Driver::DBI as base, but don't
have to.
BACKWARDS COMPATIBILITY
Version 4.0 of CGI::Session's driver specification is NOT backward compatible with the
previous specification. If you already have a driver developed to work with the previous
version you're highly encouraged to upgrade your driver code to make it compatible with
the current version. Fortunately, current driver specs are a lot easier to adapt to.
For support information see CGI::Session
LICENSING
For support and licensing see CGI::Session.
perl v5.22.1 2016-01-15 CGI::Session::Driver(3pm)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2025-07-16 19:50 @18.97.14.81 CrawledBy CCBot/2.0 (https://commoncrawl.org/faq/)