CGI::Application::Plugin::DBH - Easy DBI access from CGI::Application

       Mark Stosberg <mark@stosberg.com>

       This software is copyright (c) 2013 by Mark Stosberg.

       This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5
       programming language system itself.

perl v5.36.0                                       2022-10-14                 CGI::Application::Plugin::DBH(3pm)

       CGI::Application::Plugin::DBH adds easy access to a DBI database handle to your CGI::Application modules.
       Lazy loading is used to prevent a database connection from being made if the "dbh" method is not called
       during the request.  In other words, the database connection is not created until it is actually needed.

dbh()
        my $date = $self->dbh->selectrow_array("SELECT CURRENT_DATE");
        # again with a named handle
        $date = $self->dbh('my_handle')->selectrow_array("SELECT CURRENT_DATE");

        # OR ...

        my $dbh = $self->dbh;
        # again with a named handle
        $dbh = $self->dbh('my_other_handle');
        my $date = $dbh->selectrow_array("SELECT CURRENT_DATE");

       This method will return the current DBI database handle.  The database handle is created on the first
       call to this method, and any subsequent calls will return the same handle.

   dbh_config()
        sub cgiapp_init  {
           my $self = shift;

           # use the same args as DBI->connect();
           $self->dbh_config($data_source, $username, $auth, \%attr);

           # or to use more than one dbh
           $self->dbh_config('my_handle',
                   [ $data_source, $user, $auth, \%attr ]);
           $self->dbh_config('my_other_handle',
                   [ $data_source, $user, $auth, \%attr ]);

           # ...or use some existing handle you have
           $self->dbh_config($DBH);
           $self->dbh_config('my_handle', $DBH);   # this works too

           # Use a callback to create your owh handle that is still lazy loaded
           $self->dbh_config(sub { DBI->connect_cached(); });
        }

       Used to provide your DBI connection parameters. You can either pass in an existing DBI database handle,
       or provide the usual parameters used for DBI->connect().

       The recommended place to call "dbh_config" is in the "cgiapp_init" stage of CGI::Application.  If this
       method is called after the database handle has already been accessed, then it will die with an error
       message.

       AutomaticconfigurationusingCGI::Appinstanceparameters

       An alternative to explicitly calling "dbh_config" in your application is to rely on the presence of
       specific instance parameters that allow the plugin to configure itself.

       If you set the CGI::App parameter "::Plugin::DBH::dbh_config" to an array reference the contents of that
       array will be used as parameters to "dbh_config" (if it has not been explicitly called before).

       The code in the synopsis can be rewritten as

         use CGI::Application::Plugin::DBH (qw/dbh/);
           # no longer a need to import dbh_config

         sub cgiapp_init  {
            # you do not need to do anything here
         }

         sub my_run_mode {

           # this part stays unchanged

           ....

         }

       and in the instance script ( or instance configuration file, if you have)

          $app->param('::Plugin::DBH::dbh_config' =>
               [ $data_source, $username, $auth, \%attr ] );

       If you want to configure more than one handle, set up a hash with the handle names as keys:

           $app->param('::Plugin::DBH::dbh_config' =>
               { my_handle => [ $data_source, $username, $auth, \%attr ] ,
                 my_other_handle => [ $data_source, $username, $auth, \%attr ]
               }  );

       AutomaticconfigurationwithDBIenvironmentvariables

       If you do not set any parameters, and do not call "dbh_config", this plugin checks to see if you set the
       DBI environment variable "DBI_DSN". If present, this DSN will be used for the default handle. Note that
       the DBI documentation does not encourage using this method (especially in the context of web
       applications), that you will most likely have to also set "DBI_USER" and "DBI_PASS", and that this can
       only be used for the default handle.

   dbh_default_name()
        sub my_runmode {
           my $self = shift;

           my $old_handle_name = $self->dbh_default_name('my_handle');
           $self->some_legacy_code();  # some_legacy_code() will get "my_handle"
                                       # when it calls $self->dbh() without parameters

           $self->dbh_default_name($old_handle_name);    # Return to normal.
        }

       Can be used to alter the name of the handle that is returned by dbh() when called with no parameters. It
       can even be used to alter the name used for the unnamed handle if called before dbh_config().

       Using this method is completely optional. If you don't have a use for it don't use it. Internally the
       handle name "__cgi_application_plugin_dbh" is used to keep track of the unnamed handle unless it is
       changed by dbh_default_name() before a call to dbh_config() without a name parameter.

       CGI::Application::Plugin::DBH - Easy DBI access from CGI::Application

       Ima::DBI is similar, but has much more complexity and features.

       CGI::Application, DBI, CGI::Application::Plugin::ValidateRM

        use CGI::Application::Plugin::DBH (qw/dbh_config dbh/);

        sub cgiapp_init  {
           my $self = shift;

           # use the same args as DBI->connect();
           $self->dbh_config($data_source, $username, $auth, \%attr);

           # or to use more than one dbh
           $self->dbh_config('my_handle',
                   [ $data_source, $user, $auth, \%attr ]);
           $self->dbh_config('my_other_handle',
                   [ $data_source, $user, $auth, \%attr ]);
        }

        sub my_run_mode {
           my $self = shift;

           my $date = $self->dbh->selectrow_array("SELECT CURRENT_DATE");
           # again with a named handle
           $date = $self->dbh('my_handle')->selectrow_array("SELECT CURRENT_DATE");

           # OR ...

           my $dbh = $self->dbh;
           # again with a named handle
           $dbh = $self->dbh('my_other_handle');
           my $date = $dbh->selectrow_array("SELECT CURRENT_DATE");
        }

       version 4.04