Class::DBI::FromCGI (3pm)

  package Film;
  use Class::DBI::FromCGI;
  use base 'Class::DBI';
  # set up as any other Class::DBI class.

  _\|_PACKAGE_\|_->untaint_columns(
    printable => [qw/Title Director/],
    integer   => [qw/DomesticGross NumExplodingSheep/],
    date      => [qw/OpeningDate/],
  );

  # Later on, over in another package ...

  my $h = CGI::Untaint->new( ... );
  my $film = Film->retrieve('Godfather II');
     $film->update_from_cgi($h);

  my $new_film = Film->create_from_cgi($h);

  if (my %errors = $film->cgi_update_errors) {
    while (my ($field, $problem) = each %errors) {
      warn "Problem with $field: $problem\n";
    }
  }

  # or
  $film->update_from_cgi($h => @columns_to_update);

  # or
  $film->update_from_cgi($h => { ignore => \@cols_to_ignore,
                                 required => \@cols_needed,
                                 all => \@columns_which_may_be_empty });


  my $how = $film->untaint_type('Title'); # printable

Lots of times, Class::DBI is used in web-based applications. (In fact, coupled with a templating system that allows you to pass objects, such as Template::Toolkit, Class::DBI is very much your friend for these.)

And, as we all know, one of the most irritating things about writing web-based applications is the monotony of writing much of the same stuff over and over again. And, where there's monotony there's a tendency to skip over stuff that we all know is really important, but is a pain to write - like Taint Checking and sensible input validation. (Especially as we can still show a 'working' application without it!). So, we now have CGI::Untaint to take care of a lot of that for us.

It so happens that CGI::Untaint also plays well with Class::DBI. Class::DBI::FromCGI is a little wrapper that ties these two together.

untaint_columns

All you need to do is to 'use Class::DBI::FromCGI' in your class (or in your local Class::DBI subclass that all your other classes inherit from. You do do that, don't you?).

Then, in each class in which you want to use this, you declare how you want to untaint each column:

_\|_PACKAGE_\|_->untaint_columns( printable => [qw/Title Director/], integer => [qw/DomesticGross NumExplodingSheep/], date => [qw/OpeningDate/], );

(where the keys are the CGI::Untaint package to be used, and the values a listref of the relevant columns).

update_from_cgi

When you want to update based on the values coming in from a web-based form, you just call:

$obj->update_from_cgi($h => @columns_to_update);

If every value passed in gets through the CGI::Untaint process, the object will be updated (but not committed, in case you want to do anything else with it). Otherwise the update will fail (there are no partial updates), and $obj->cgi_update_errors will tell you what went wrong (as a hash of problem field => error from CGI::Untaint).

create_from_cgi

Similarly, if you wish to create a new object, then you can call:

my $obj = Class->create_from_cgi($h => @columns_to_update);

If this fails, $obj will be a defined object, containing the errors, as with an update, but will not contain the values submitted, nor have been written to the database.

untaint_type

my $how = $film->untaint_type('Title'); # printable

This tells you how we're going to untaint a given column.

cgi_update_errors

if (my %errors = $film->cgi_update_errors) { while (my ($field, $problem) = each %errors) { warn "Problem with $field: $problem\n"; } }

This returns a hash of any errors when updating. Despite its name it also applies when inserting.

As Class::DBI knows all its columns, you don't even have to say what columns you're interested in, unless it's a subset, as we can auto-fill these:

$obj->update_from_cgi($h);

You can also specify columns which must be present, or columns to be ignored even if they are present:

$film->update_from_cgi($h => { all => \@all_columns, # auto-filled if left blank ignore => \@cols_to_ignore, required => \@cols_needed, });

Doesn't this all make your life so much easier?

Don't try to update the value of your primary key. Class::DBI doesn't like that. If you try to do this it will be silently skipped.

If you haven't set up any 'untaint_column' information for a column which you later attempt to untaint, then we try to call $self->column_type to ascertain the default handler to use. Currently this will only use if you're using Class::DBI::mysql, and only for certain column types.

Class::DBI. CGI::Untaint. Template.

Tony Bowden

Please direct all correspondence regarding this module to:

  [email protected]

Copyright (C) 2001-2005 Kasei. All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.