sub new {
  ref (my $class = shift) && croak 'class name needed in constructor';
  my $self = {@_};
  $self->{$_} = $self->{$_} || '' for(qw/db user pass/);
  bless $self, $class;
  $self->connect();
  $self;
}

sub connect {
  my $self = shift;
  my $dbh = DBI->connect("dbi:mysql:$self->{'db'}", 
                                                $self->{'user'}, 
                                                $self->{'pass'})
                     || croak "DB-error: $DBI::errstr\n";
  $self->{'db_handle'} = $dbh;
}

my %parameter = @_;

my %option = (
                '-db'   => 'required',
                '-user' => 'required',
                '-pass' => 'required',
                '-extra'        => 'optional',
        );

foreach my $parameter (keys %parameter){
        unless (exists $option{$parameter}){
                warn "Unknown parameter '$parameter'";
                next;
        }

        # und so weiter...
}

sub check_mysql_params {
    my( $self ) = @_;

    foreach my $attr ( qw( db username pass ) ) {
        unless( defined $self->$attr ) {
            croak( "Error: attribute '$attr' not set" );
        }
    }
    # eventuell hier noch den connect testen

    return $self;
} # check_mysql_params

sub init {
    my( $self, %params ) = @_;

    # parameter hier setzen
    
    my $driver = $self->driver || 'mysql';
    
    my $checkDriverParamsMethod = "check_${driver}_params";
    if( $self->can( $checkDriverParamsMethod ) {
        $self->$checkDriverParamsMethod;
    }
    else {
        croak "Error: no method '$checkDriverParamsMethod' existing";
    }

} # init

my @objectInterfaceMethods = qw( db user pass db_handle );

foreach my $method ( @objectInterfaceMethods ) {

    # anonyme sub erzeugen
    my $sub = sub {
        my( $self, @params ) = @_;

        $self->{ $method } = $params[0] if @params;

        return $self->{ $method };
    }; # sub

    # sub in der symboltabelle unter dem Namen $method verankern
    no strict 'refs';
    *{ $method } = $sub;

} # foreach

sub new {
    my( $class, @params ) = @_;

    croak 'class name needed in constructor' if ref $class;

    my $self = bless( {}, $class );

    $self->init( @params ) if scalar @params;

    return $self;
}

sub init {
    my( $self, %params ) = @_;

    foreach my $param ( keys %params ) {
        if( $self->can( $param ) ) {
            $self->$param( $params{$param} );
        }
        else {
            croak( "Invalid param '$param'" );
        }
    } # foreach

   # hier eventuell noch ueberpruefen, ob alle benoetigten parameter gesetzt sind
   # ...

  $self->connect();

  return $self;
}

sub connect {
    my $self = shift;
    my $dbh = DBI->connect("dbi:mysql:" . $self->db, 
                                                $self->user, 
                                                $self->pass)
                     or croak "DB-error: $DBI::errstr\n";
    $self->db_handle( $dbh );

    return $self;
}