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¶
- •
- All driver .pm files must be lowercase!
- •
- 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.