Apache::Session help storing a complex data structure

[B-A-T]

Hi, I am trying to store a data structure in using Apache::Session::MySQL.
The session creation and retrieval works fine for scalar values,HoH or Array etc,
but the session is not written if i try to store a tree data structure (N-ary tree http://search.cpan.org/~rkinyon/Tree-1.01/lib/Tree.pm) The code is as follows: --

my %session;

tie %session,'Apache::Session::MySQL', undef, { 
    DataSource => 'dbi:mysql:sessions',
   UserName => 'login',
    Password => 'pass',
    LockDataSource => 'dbi:mysql:sessions',
    LockUserName   => 'login',
    LockPassword   => 'pass' };

my $id = $session{_session_id};
$session{TIMESTAMP} =time;
$session{tree} = $treeP; ## $treeP is a N-ary Tree

$session{uname} = $uname;
untie(%session) || die " Cant untie! \n";

##-- in another code
my %session1;

tie %session1,'Apache::Session::MySQL', undef, {
    DataSource => 'dbi:mysql:sessions',
   UserName => 'login',
    Password => 'pass',
    LockDataSource => 'dbi:mysql:sessions',
    LockUserName   => 'login',
    LockPassword   => 'pass' };


my $u = $session1{uname}; ## this value is undef if I try to store the
+ tree as well in the above code

print STDERR "name $u \n"; 
untie(%session1) or die "CANT CLOSE!! \n";

========

Can anyone help?

Thanks in advance...

cheers!

[ikegami]

The docs for Apache::Session say that Storable (and more specifically nfreeze and thaw) are used to serialize the data. But when I try to freeze a Tree, I get a fatal error.

use strict;
use warnings;

use Tree         qw( );
use Storable     qw( nfreeze thaw );
use Data::Dumper qw( Dumper );

my $tree = Tree->new( 'root' );
my $child = Tree->new( 'child' );
$tree->add_child( $child );

print(Dumper(thaw(nfreeze($tree))));

Can't store CODE items at ..\..\lib\Storable.pm (autosplit into ..\..\
+lib\auto\Storable\_freeze.al) line 339, at script.pl line 12

Are you getting any errors? I haven't tried actually using Apache::Session. Can that be used from a command line script?

[B-A-T]

Thankyou for replying,and Yes, the Command line script works. But, you are correct - the problem is with serializing the Tree, and not Apache::Session. I couldnt catch it myself.


So, the only option with me is: creating/using another data structure?

It would have been immense help, if Tree could work.

Thanks!

[CountZero]

Did you try other serializers?

Apache::Session::Flex allows you to choose other serializers (such as Apache::Session::Serialize::YAML) that may perhaps be able to work with trees.

Update: Using ikegami's script but replacing Storable with YAML seems to work:

use strict;
use warnings;

use Tree         qw( );
use YAML         qw( Dump Load );
use Data::Dumper qw( Dumper );

my $tree = Tree->new( 'root' );
my $child = Tree->new( 'child' );
$tree->add_child( $child );

print(Dumper(Load(Dump($tree))));

Output:

$VAR1 = bless( {
                 '_parent' => \undef,
                 '_value' => 'root',
                 '_children' => [
                                  bless( {
                                           '_parent' => $VAR1,
                                           '_value' => 'child',
                                           '_children' => [],
                                           '_meta' => {},
                                           '_depth' => '1',
                                           '_error_handler' => sub { "
+DUMMY" },
                                           '_width' => '1',
                                           '_handlers' => {
                                                            'value' =>
+ [],
                                                            'add_child
+' => [],
                                                            'remove_ch
+ild' => []
                                                          },
                                           '_root' => $VAR1,
                                           '_height' => '1',
                                           '_last_error' => undef
                                         }, 'Tree' )
                                ],
                 '_meta' => {},
                 '_depth' => '0',
                 '_error_handler' => $VAR1->{'_children'}[0]{'_error_h
+andler'},
                 '_width' => '1',
                 '_handlers' => {
                                  'value' => [],
                                  'add_child' => [],
                                  'remove_child' => []
                                },
                 '_root' => $VAR1,
                 '_height' => '2',
                 '_last_error' => undef
               }, 'Tree' );

[B-A-T]

no it dint work ! :( But a little improvement the other variables(name, timestamp) are stored normally, only the tree is not being written. :|

..

[jasonk]

You don't indicate what the error messages are, but Tree objects include code references. In order to serialize them with Storable, you either need to have a recent version of Storable (after 2.05) and set $Storable::Deparse to a true value, to allow Storable to serialize the code reference, or prevent the code references from being serialized (see STORABLE_freeze and STORABLE_thaw in Storable).