+---

+date: 2010-03-19T00:00:00Z

+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/perldancer/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:

+

+```perl

+set serializer => 'JSON';

+```

+

+or in your configuration file:

+

+```yaml

+serializer: "JSON"

+```

+

+## A simple handler

+

+Let's create a new dancer application (you can fetch the source on [my git server](http://git.lumberjaph.net/p5-dancer-rest.git/) :

+

+```bash

+% dancer -a dancerREST

+% cd dancerREST

+% vim dancerREST.pm

+```

+

+then

+

+```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;

+```

+

+We can test if everything works as expected:

+

+```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"}

+```

+

+Now we add a method to fetch a list of users, and a method to get a

+specific user:

+

+```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;

+};

+```

+

+If we want to fetch the full list:

+

+```sh

+curl -H "Content-Type: application/json" http://localhost:5000/api/user/

+# => [{"name":"foo","id":"1"}]

+```

+

+and a specific user:

+

+```sh

+curl -H "Content-Type: application/json" http://localhost:5000/api/user/1

+# => {"name":"foo"}

+```

+

+## 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

+

+```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;

+ }

+}

+```

+

+If we want to simulate an AJAX query:

+

+```bash

+% curl -H "X-Requested-With: XMLHttpRequest" http://localhost:5000/user/1

+```

+

+and we will obtain our result in JSON. But we can also test without the X-Requested-With:

+

+```bash

+% curl http://localhost:5000/user/1

+```

+

+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).