A Simple Plack/DBI Example

This is a very old article. It has been imported from older blogging software, and the formatting, images, etc may have been lost. Some links may be broken. Some of the information may no longer be correct. Opinions expressed in this article may no longer be held.

In A Simple Mojolicious/DBI Example Joel Berger demonstrates how to build a very simple CRUD web app (well, a CR one anyway) using Mojolicious and DBI. I was impressed at how concise it was, and wondered how my preferred technology stack would compare.

I’m not a fan of template languages, preferring DOM manipulation. And rather than Mojo, I’m using Plack here. Anyway, this is what I came up with…

#!/usr/bin/env plackup

use v5.14;
use DBI;
use HTML::HTML5::Parser;
use HTML::HTML5::Writer;
use Plack::Request;
use Plack::Response;

# connect to database
my $dbh = 'DBI'->connect("dbi:SQLite:database.db","","") or die "Could not connect";
my ($insert, $select);

while (1) {
   # create insert and select statements
   $insert = eval { $dbh->prepare('INSERT INTO people VALUES (?,?)') };
   $select = eval { $dbh->prepare('SELECT * FROM people') };
   # break out of loop if statements prepared
   last if $insert && $select;

   # if statements didn't prepare, assume its because the table doesn't exist
   warn "Creating table 'people'\n";
   $dbh->do('CREATE TABLE people (name varchar(255), age int);');

my $template = 'HTML::HTML5::Parser'->load_html(IO => \*DATA);
my $writer   = 'HTML::HTML5::Writer'->new(markup => 'html', polyglot => 1);

# the PSGI app itself
my $app = sub {
   my $req = 'Plack::Request'->new(shift);
   my $res = 'Plack::Response'->new(200);

   if ($req->method eq 'POST') {
      $insert->execute(map $req->parameters->{$_}, qw( name age ));
      $res->redirect( $req->base );
   else {
      my $page  = $template->cloneNode(1);
      my $table = $page->getElementsByTagName('table')->get_node(1);
      while (my @row = $select->fetchrow_array) {
         my $tr = $table->addNewChild($table->namespaceURI, 'tr');
         $tr->appendTextChild(td => $_) for @row;
      $res->body( $writer->document($page) );


<!DOCTYPE html>
<form action="insert" method="post">
   Name: <input type="text" name="name"> 
   Age: <input type="text" name="age">
   <input type="submit" value="Add">
Data: <br>
<table border="1">