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# $Id$
# BioPerl module for Bio::DB::DBI::TransactionListener
# Please direct questions and support issues to <>
# Cared for by Hilmar Lapp <hlapp at>
# Copyright Hilmar Lapp
# You may distribute this module under the same terms as perl itself
# (c) Hilmar Lapp, hlapp at, 2003.
# (c) GNF, Genomics Institute of the Novartis Research Foundation, 2003.
# You may distribute this module under the same terms as perl itself.
# Refer to the Perl Artistic License (see the license accompanying this
# software package, or see
# for the terms under which you may use, modify, and redistribute this module.
# POD documentation - main docs before the code
=head1 NAME
Bio::DB::DBI::TransactionListener - a simple transaction listener
# see method section
This object is the contract and at the same time a simple (neutral)
implementation of a transaction listener.
Transaction listeners are notified before and after commit and
rollback on transactions as represented by a
Bio::DB::DBI::Transaction objects.
Note that this is a very loose contract in the sense that it is not
enforced. Therefore it serves more as a guideline of what you *can*
do rather than what you have to do.
You may currently choose between 3 different options on how to listen
to transactions:
- write your own transaction listener that inherits from this
class and overrides methods as suitable, then use your class to
add listeners to Transactions
- let your adaptor or persistent object module inherit from this
class and thereby make it a listener-compliant object that you
can then use to register with Transactions
- register any object with Transaction that implements at least
one of the methods defined here (if it implements none then
what's the point?). Transaction will only call the methods
defined here if the listener actually implements them.
=head2 Mailing Lists
User feedback is an integral part of the evolution of this and other
Bioperl modules. Send your comments and suggestions preferably to
the Bioperl mailing list. Your participation is much appreciated. - General discussion - About the mailing lists
=head2 Support
Please direct usage questions or support issues to the mailing list:
rather than to the module maintainer directly. Many experienced and
reponsive experts will be able look at the problem and quickly
address it. Please include a thorough description of the problem
with code and data examples if at all possible.
=head2 Reporting Bugs
Report bugs to the Bioperl bug tracking system to help us keep track
of the bugs and their resolution. Bug reports can be submitted via
the web:
=head1 AUTHOR - Hilmar Lapp
Email hlapp at
Describe contact details here
Additional contributors names and emails here
The rest of the documentation details each of the object methods.
Internal methods are usually preceded with a _
# Let the code begin...
package Bio::DB::DBI::TransactionListener;
use vars qw(@ISA);
use strict;
# Object preamble - inherits from Bio::Root::Root
use Bio::Root::Root;
@ISA = qw(Bio::Root::Root );
my $counter = 1;
=head2 new
Title : new
Usage : my $obj = Bio::DB::DBI::TransactionListener->new();
Function: Builds a new Bio::DB::DBI::TransactionListener object
Returns : an instance of Bio::DB::DBI::TransactionListener
Args :
sub new {
my($class,@args) = @_;
my $self = $class->SUPER::new(@args);
return $self;
=head2 register_sub
Title : register_sub
Usage :
Function: Register an anonymous code block for being executed in
one of the listener methods.
This method is probably mostly useful for testing purposes,
but who knows.
You may call this as a class method or an object method.
Example :
Returns : an instance of this class with the supplied anonymous
function overriding the specified listener method
Args : the code reference to register
the name(s) of the interface method(s) to register it for
(optional, if not specified the code block will be
registered for all 4 methods)
sub register_sub{
my ($class,$code,@meths) = @_;
@meths = ("before_commit","after_commit",
"before_rollback","after_rollback") unless @meths;
$class = ref($class) || $class;
$class .= ++$counter;
my $obj = bless {}, $class;
foreach my $meth (@meths) {
*{"$class::$meth"} = $code;
return $obj;
=head1 TransactionListener interface methods
The following methods define the interface for TransactionListeners.
=head2 before_commit
Title : before_commit
Usage :
Function: Called before a commit is issued.
Any listener may veto a pending commit by returning
false. The default implementation returns true.
Example :
Returns : TRUE if the transaction is good to be committed, and
FALSE if it is vetoed.
Args : none
sub before_commit{
return 1;
=head2 after_commit
Title : after_commit
Usage :
Function: Called after a commit was issued.
The default implementation here does nothing.
Example :
Returns : ignored
Args : none
sub after_commit{
return 1;
=head2 before_rollback
Title : before_rollback
Usage :
Function: Called before a rollback is issued.
A listener cannot veto a pending rollback. The return value
and even thrown exceptions will be ignored by Transaction.
Example :
Returns : ignored
Args : none
sub before_rollback{
return 1;
=head2 after_rollback
Title : after_rollback
Usage :
Function: Called after a rollback is issued.
Example :
Returns : ignored
Args : none
sub after_rollback{
return 1;
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