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---
layout: post
summary: In which we see that it's easy to create REST interface with Dancer.
title: Easily create REST interface with the Dancer 1.170
---
This week, with [Alexi](http://www.sukria.net/fr/)'s help, [I've been working on](http://github.com/sukria/Dancer) to add auto-(de)serialization to Dancer's request. This features will be available in the next [Dancer](http://perldancer.org/) version, the 1.170 (which will be out before April).
The basic idea was to provides to developer a simple way to access data that have been send in a serialized format, and to properly serialize the response.
At the moment, the supported serializers are :
* Dancer::Serialize::JSON
* Dancer::Serialize::YAML
* Dancer::Serialize::XML
* Dancer::Serialize::Mutable
## Configuring an application to use the serializer
To activate serialization in your application:
{% highlight perl %}
set serializer => 'JSON';
{% endhighlight %}
or in your configuration file:
{% highlight yaml %}
serializer: "JSON"
{% endhighlight %}
## A simple handler
Let's create a new dancer application (you can fetch the source on [GitHub](http://github.com/franckcuny/dancerREST) :
{% highlight bash %}
% dancer -a dancerREST
% cd dancerREST
% vim dancerREST.pm
{% endhighlight %}
then
{% highlight perl %}
package dancerREST;
use Dancer ':syntax';
my %users = ();
post '/api/user/' => sub {
my $params = request->params;
if ($params->{name} && $params->{id}) {
if (exists $users{$params->{id}}) {
return {error => "user already exists"};
}
$users{$params->{id}} = {name => $params->{name}};
return {id => $params->{id}, name => $params->{name}};
}
else {
return {error => "name is missing"};
}
};
true;
{% endhighlight %}
We can test if everything works as expected:
{% highlight bash %}
% plackup app.psgi &
% curl -H "Content-Type: application/json" -X POST http://localhost:5000/api/user/ -d '{"name":"foo","id":1}'
# => {"name":"foo","id":"1"}
{% endhighlight %}
Now we add a method to fetch a list of users, and a method to get a
specific user:
{% highlight perl %}
# return a specific user
get '/api/user/:id' => sub {
my $params = request->params;
if (exists $users{$params->{id}}) {
return $users{$params->{id}};
}
else {
return {error => "unknown user"};
}
};
# return a list of users
get '/api/user/' => sub {
my @users;
push @users, {name => $users{$_}->{name}, id => $_}
foreach keys %users;
return \@users;
};
{% endhighlight %}
If we want to fetch the full list:
{% highlight sh %}
curl -H "Content-Type: application/json" http://localhost:5000/api/user/
# => [{"name":"foo","id":"1"}]
{% endhighlight %}
and a specific user:
{% highlight sh %}
curl -H "Content-Type: application/json" http://localhost:5000/api/user/1
# => {"name":"foo"}
{% endhighlight %}
## The mutable serializer
The mutable serializer will try to load an appropriate serializer guessing from the **Content-Type** and **Accept-Type** header. You can also overload this by adding a **content_type=application/json** parameter to your request.
While setting your serializer to mutable, your let your user decide which format they prefer between YAML, JSON and XML.
## And the bonus
Dancer provides now a new method to the request object : `is_ajax`. Now you can write something like
{% highlight perl %}
get '/user/:id' => sub {
my $params = request->params;
my $user = $users{$params->{id}};
my $result;
if (!$user) {
_render_user({error => "unknown user"});
}
else {
_render_user($user);
}
};
sub _render_user {
my $result = shift;
if (request->is_ajax) {
return $result;
}
else {
template 'user.tt', $result;
}
}
{% endhighlight %}
If we want to simulate an AJAX query:
{% highlight bash %}
% curl -H "X-Requested-With: XMLHttpRequest" http://localhost:5000/user/1
{% endhighlight %}
and we will obtain our result in JSON. But we can also test without the X-Requested-With:
{% highlight bash %}
% curl http://localhost:5000/user/1
{% endhighlight %}
and the template will be rendered.
Hope you like this new features. I've also been working on something similar for [Tatsumaki](http://github.com/miyagawa/tatsumaki).
|
