xmpl - the API for browsers


We will take a closer look at the implementation for the API available to the browsers in xmpl. This post is part of a series.

In previous post xmpl - the key/value API we took a look at the basic API provided by xmpl, that is mainly geared at being consumed in a machine to machine way.

An example application, though, is also something useful to look at from the browser, which means generating HTML pages and leveraging GET and POST methods “only” (at least if we want to avoid using Javascript to keep things simple).

The GET verb is addressed by a function that gets all the key/value pairs as a hash and calls the render method, which will transform these data into a page according to the template provided by the function template_index:

get '/' => sub ($c) {
   my %args = (inline => template_index(), kvstore => kvstore()->origin);
   if (! ($args{kv} = eval { kvstore()->as_hash })) {
      $args{kv} = {};
      $args{error} = 'could not read key/value pairs from store';

We will not get into the details of the template, you an take a look at it here.

The POST verb is overloaded with two sub-actions, one for adding (or modifying) a key/value pair, one for deleting it. This is tracked via parameter sub-action:

post '/' => sub ($c) {
   eval {
      my $sub_action = $c->param('sub-action');
      if ($sub_action eq 'delete') {
         $c->flash(info => 'element removed');
      else {
         kvstore()->set($c->param('key'), $c->param('value'));
         $c->flash(info => 'element added');
   } or $c->flash(error => 'action failed');

This always redirects to the GET, so that we keep it simple.

The last part is the overriding of the favicon.ico icon, to add some sugar (the favicon function can be seen here):

get '/favicon.ico' => sub ($c) {
      status => 200,
      data => favicon(),
      format => 'png',

Except that… this does not work.

Mojolicious generats a favicon by itself, and the request never gets to hit the route above (which is somehow weird, in my opinion). The solution is to explicitly get rid of the internally generated one:

delete app->static->extra->{'favicon.ico'};

That’s it! An ugly, bare-bones, very 90-esque page that is shown in a real browser!

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