Re: DBI and modules
From: Doug Silver (dsilver_at_urchin.com)
Date: 10/17/03
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To: "Simon Taylor" <set@nortelnetworks.com>, "'dbi-users@perl.org'" <dbi-users@perl.org> Date: Fri, 17 Oct 2003 10:38:29 -0700
On Friday 17 October 2003 08:22 am, Simon Taylor wrote:
> I am trying to create a module that sets ups environment variables from
> another module, creates a database handle and passes it back to the calling
> script.
> I understand that an object exists as long as there is a reference to it
> but cant quite see why this code generates the following errors when it
> tries to destroy the dbh even though it is always an object in the hash?
> No doubt I am confused about a fundamental here.
>
> Issuing rollback() for database handle being DESTROY'd without explicit
> disconnect() at ./poe_ctrl.pl line 38.
> $VAR1 = bless( {
> '_dbh' => bless( {}, 'DBI::db' )
> }, 'SDU::DB' );
> Issuing rollback() for database handle being DESTROY'd without explicit
> disconnect().
>
> ---------------------------------------------------------------------------
>-
> ---------------------------------------------------------------------------
>- ------------------
> Script to create the connection poe_ctrl.pl
>
> use warnings;
> use strict;
> use Data::Dumper;
> use POE qw(Wheel::Run Filter::Reference);
> use SDU::CommandIterator;
> use SDU::DB;
> use SDU::Config;
> sub MAX_CONCURRENT_TASKS () { 5 }
>
>
> # Create database connection
> my $dbh = SDU::DB->new;
> print Dumper($dbh);
> exit;
>
> ---------------------------------------------------------------------------
>-
> ---------------------------------------------------------------------------
>- --------------------
> Package to create the connection
>
> package SDU::DB;
> require 5.008 ;
> use SDU::Config;
> use strict;
> use Carp;
> use Carp qw(cluck);
> use DBI;
> use DBI qw(:sql_types);
> use DBD::Oracle;
> use DBD::Oracle qw(:ora_types);
> use TNBException;
>
> sub new {
> my $class = shift;
> my $SC = SDU::Config->new;
> my $DB = { _dbh => &ConnectToOracle($SC)
> };
> my $DC = &ConnectToOracle($SC);
> my $self = bless $DB, $class;
> return $self;
> }
>
>
> sub ConnectToOracle{
> my ($SC) = @_;
> $ENV{ORACLE_HOME}=$SC->{ORA_HOME};
> $ENV{TWO_TASK}=$SC->{ORA_SID};
> $ENV{ORACLE_SID}=$SC->{ORA_SID};
> my $combined=$SC->{ORA_USER}."@".$SC->{ORA_SID};
> my $trace_level=0;
> my $dbh = undef;
> $dbh = DBI->connect('dbi:Oracle:',$combined , $SC->{ORA_PASS}) or throw
> TNBCriticalException($dbh->errstr);
> $dbh->func( 1000000, 'dbms_output_enable' );
> $dbh->{RaiseError} = 1;
> $dbh->{PrintError} = 0;
> $dbh->{AutoCommit} = 0;
> $dbh->trace($trace_level);
> return $dbh;
> }
>
> 1;
>
> Simon Taylor
> Managed Services Technology Consultant
> Nortel Networks
> p - 01279 404289 (ESN 742 4289)
> m - 07740 533743 (ESN 748 3743)
> e - set@nortelnetworks.com
>
> "I code therefore I am"
Hi Simon -
I am also in the process of writing something similar and came up with the
following:
#this will automatically handle all DBI calls that we make
#using this module, e.g. disconnect, selectrow_array, do, etc
sub AUTOLOAD {
my $self = shift;
my $name = our $AUTOLOAD;
$name=~s/.*::DB::(.*)/$1/;
#safely do a db disconnect if the script is not called
#from the web server
return $self->disconnect if $name=~/DESTROY$/ && ! defined
$ENV{SERVER_SOFTWARE};
return $self->{dbh}->$name(@_);
}
If you run some tests, particularly from command line, you'll see that when
the script ends, it always calls the DESTROY method, and that's where the
AUTOLOAD comes into play and it will safely disconnect from the database
handle.
Of course, YMMV!
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Doug Silver Network Manager Urchin Software Corp. http://www.urchin.com ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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