Raisin - A REST API microframework for Perl.


version 0.94


    use HTTP::Status qw(:constants);
    use List::Util qw(max);
    use Raisin::API;
    use Types::Standard qw(HashRef Any Int Str);

    my %USERS = (
        1 => {
            first_name => 'Darth',
            last_name => 'Wader',
            password => 'deathstar',
            email => '',
        2 => {
            first_name => 'Luke',
            last_name => 'Skywalker',
            password => 'qwerty',
            email => '',

    plugin 'Logger', fallback => 1;
    app->log( debug => 'Starting Raisin...' );

    middleware 'CrossOrigin',
        origins => '*',
        methods => [qw/DELETE GET HEAD OPTIONS PATCH POST PUT/],
        headers => [qw/accept authorization content-type api_key_token/];

    plugin 'Swagger';

        title => 'A POD synopsis API',
        description => 'An example of API documentation.',
        #terms_of_service => '',

        contact => {
            name => 'Artur Khabibullin',
            url => '',
            email => '',

        license => {
            name => 'Perl license',
            url => '',

    desc 'Users API';
    resource users => sub {
        summary 'List users';
            optional('start', type => Int, default => 0, desc => 'Pager (start)'),
            optional('count', type => Int, default => 10, desc => 'Pager (count)'),
        get sub {
            my $params = shift;

            my @users
                = map { { id => $_, %{ $USERS{$_} } } }
                  sort { $a <=> $b } keys %USERS;

            my $max_count = scalar(@users) - 1;
            my $start = $params->{start} > $max_count ? $max_count : $params->{start};
            my $end = $params->{count} > $max_count ? $max_count : $params->{count};

            my @slice = @users[$start .. $end];
            { data => \@slice }

        summary 'List all users at once';
        get 'all' => sub {
            my @users
                = map { { id => $_, %{ $USERS{$_} } } }
                  sort { $a <=> $b } keys %USERS;
            { data => \@users }

        summary 'Create new user';
            requires('user', type => HashRef, desc => 'User object', group {
                requires('first_name', type => Str, desc => 'First name'),
                requires('last_name', type => Str, desc => 'Last name'),
                requires('password', type => Str, desc => 'User password'),
                optional('email', type => Str, default => undef, regex => qr/.+\@.+/, desc => 'User email'),
        post sub {
            my $params = shift;

            my $id = max(keys %USERS) + 1;
            $USERS{$id} = $params->{user};

            { success => 1 }

        desc 'Actions on the user';
        params requires('id', type => Int, desc => 'User ID');
        route_param 'id' => sub {
            summary 'Show user';
            get sub {
                my $params = shift;
                $USERS{ $params->{id} };

            summary 'Delete user';
            del sub {
                my $params = shift;
                delete $USERS{ $params->{id} };



Raisin is a REST API microframework for Perl. It's designed to run on Plack, providing a simple DSL to develop RESTful APIs easily. It was inspired by Grape.

CPAN version




Returns the Raisin app. Seldom needed, because most Raisin::API methods invoke the app directly.


Adds a route to an application. namespace is a synonym for resource.

    resource user => sub { ... };


Defines a route parameter as a resource id which can be anything if type isn't specified for it.

    route_param id => sub { ... };

Raisin allows you to nest route_param:

    params requires => { name => 'id', type => Int };
    route_param id => sub {
        get sub { ... };

        params requires => { name => 'sub_id', type => Int };
        route_param sub_id => sub {


Specifies the content types produced by resource.

    produces ['text', 'json'];

The argument is an array reference of strings corresponding to the keys used by register_encoder. This array is compared with the Accept header of the request to decide what content-type will actually be returned from a given invocation of resource.

del, get, patch, post, put, head, options

Shortcuts to add a route restricted to the corresponding HTTP method.

    get sub { 'GET' };

    del 'all' => sub { 'OK' };

        requires('id', type => Int),
        optional('key', type => Str),
    get sub { 'GET' };

    desc 'Put data';
        required('id', type => Int),
        optional('name', type => Str),
    put 'all' => sub {


Adds a description to resource or any of the HTTP methods. Useful for OpenAPI as it's shown there as a description of an action.

    desc 'Some long explanation about an action';
    put sub { ... };

    desc 'Some exaplanation about a group of actions',
    resource => 'user' => sub { ... }


Same as "desc" but shorter.

    summary 'Some summary';
    put sub { ... };


Tags can be used for logical grouping of operations by resources or any other qualifier. Using in API description.

    tags 'delete', 'user';
    delete sub { ... };

By default tags are added automatically based on it's namespace but you always can overwrite it using the function.


Describes response object which will be used to generate OpenAPI description.

    entity 'MusicApp::Entity::Album';
    get {
        my $albums = $schema->resultset('Album');
        present data => $albums, with => 'MusicApp::Entity::Album';


Defines validations and coercion options for your parameters. Can be applied to any HTTP method and/or "route_param" to describe parameters.

        requires('name', type => Str),
        optional('start', type => Int, default => 0),
        optional('count', type => Int, default => 10),
    get sub { ... };

        requires('id', type => Int, desc => 'User ID'),
    route_param 'id' => sub { ... };

For more see "Validation-and-coercion" in Raisin.


Specifies default API format mode when formatter isn't specified by API user. E.g. if URI is asked without an extension (json, yaml) or Accept header isn't specified the default format will be used.

Default value: YAML.

    api_default_format 'json';

See also "API-FORMATS" in Raisin.


Restricts API to use only specified formatter to serialize and deserialize data.

Already exists Raisin::Encoder::JSON, Raisin::Encoder::YAML, and Raisin::Encoder::Text, but you can always register your own using "register_encoder".

    api_format 'json';

See also "API-FORMATS" in Raisin.


Sets up an API version header.

    api_version 1.23;


Loads a Raisin module. A module options may be specified after the module name. Compatible with Kelp modules.

    plugin 'Swagger';


Adds a middleware to your application.

    middleware '+Plack::Middleware::Session' => { store => 'File' };
    middleware '+Plack::Middleware::ContentLength';
    middleware 'Runtime'; # will be loaded Plack::Middleware::Runtime


Mounts multiple API implementations inside another one. These don't have to be different versions, but may be components of the same API.


    package RaisinApp;

    use Raisin::API;

    api_format 'json';

    mount 'RaisinApp::User';
    mount 'RaisinApp::Host';



Registers a third-party parser (decoder).

    register_decoder(xml => 'My::Parser::XML');

See also Raisin::Decoder.


Registers a third-party formatter (encoder).

    register_encoder(xml => 'My::Formatter::XML');

See also Raisin::Encoder.


Returns the PSGI application.



Provides quick access to the Raisin::Request object for the current route.

Use req to get access to request headers, params, env, etc.

    use DDP;
    p req->headers;
    p req->params;
    p req->env;

    say req->header('X-Header');

See also Plack::Request.


Provides quick access to the Raisin::Response object for the current route.

Use res to set up response parameters.

    res->headers(['X-Application' => 'Raisin Application']);

See also Plack::Response.


Returns request parameters. Without an argument will return an array of all input parameters. Otherwise it will return the value of the requested parameter.

Returns Hash::MultiValue object.

    say param('key'); # -> value
    say param(); # -> { key => 'value', foo => 'bar' }


Returns all declared parameters even if there is no value for a param.

See "Declared-parameters" in Raisin.


Returns psgix.session hash. When it exists, you can retrieve and store per-session data.

    # store param
    session->{hello} = 'World!';

    # read param
    say session->{name};


Raisin hash a built-in present method, which accepts two arguments: an object to be presented and an options associated with it. The options hash may include with key, which is defined the entity to expose. See Raisin::Entity.

    my $artists = $schema->resultset('Artist');

    present data => $artists, with => 'MusicApp::Entity::Artist';
    present count => $artists->count;

Raisin::Entity supports DBIx::Class and Rose::DB::Object.

For details see examples in examples/music-app and Raisin::Entity.


When you add a route for a resource, a route for the OPTIONS method will also be added. The response to an OPTIONS request will include an "Allow" header listing the supported methods.

    get 'count' => sub {
        { count => $count };

        requires('num', type => Int, desc => 'Value to add to the count.'),
    put 'count' => sub {
        my $params = shift;
        $count += $params->{num};
        { count: $count };

    curl -v -X OPTIONS http://localhost:5000/count

    > OPTIONS /count HTTP/1.1
    > Host: localhost:5000
    * HTTP 1.0, assume close after body
    < HTTP/1.1 204 No Content
    < Allow: GET, OPTIONS, PUT

If a request for a resource is made with an unsupported HTTP method, an HTTP 405 (Method Not Allowed) response will be returned.

    curl -X DELETE -v http://localhost:3000/count

    > DELETE /count HTTP/1.1
    > Host: localhost:5000
    * HTTP 1.0, assume close after body
    < HTTP/1.1 405 Method Not Allowed
    < Allow: OPTIONS, GET, PUT


Request parameters are available through the params HASH. This includes GET, POST and PUT parameters, along with any named parameters you specify in your route strings.

Parameters are automatically populated from the request body on POST and PUT for form input, JSON and YAML content-types.

The request:

    curl localhost:5000/data -H Content-Type:application/json -d '{"id": "14"}'

The Raisin endpoint:

    post data => sub { param('id') };

Multipart POSTs and PUTs are supported as well.

In the case of conflict between either of:

  • path parameters;

  • GET, POST and PUT parameters;

  • contents of request body on POST and PUT;

Path parameters have precedence.

Query string and body parameters will be merged (see "parameters" in Plack::Request)

Declared parameters

Raisin allows you to access only the parameters that have been declared by you in "params" in Raisin block.

By default you can get all declared parameter as a first argument passed to your route subroutine.


    api_format 'json';

    post data => sub {
        my $params = shift;
        { data => $params };


    curl -X POST -H "Content-Type: application/json" localhost:5000/signup -d '{"id": 42}'


    { "data": nil }

Once we add parameters block, Raisin will start return only the declared parameters.


    api_format 'json';

        requires('id', type => Int),
        optional('email', type => Str)
    post data => sub {
        my $params = shift;
        { data => $params };


    curl -X POST -H "Content-Type: application/json" localhost:5000/signup -d '{"id": 42, "key": "value"}'


    { "data": { "id": 42 } }

By default declared parameters don't contain parameters which have no value. If you want to return all parameters you can use the include_missing function.


    api_format 'json';

        requires('id', type => Int),
        optional('email', type => Str)
    post data => sub {
        my $params = shift;
        { data => include_missing($params) };


    curl -X POST -H "Content-Type: application/json" localhost:5000/signup -d '{"id": 42, "key": "value"}'


    { "data": { "id": 42, "email": null } }

Validation and coercion

You can define validations and coercion options for your parameters using a "params" in Raisin block.

Parameters can requires value or can be optional. optional parameters can have default value.

        requires('name', type => Str),
        optional('count', type => Int, default => 10),
    get sub {
        my $params = shift;
        "$params->{count}: $params->{name}";

Note that default values will NOT be passed through to any validation options specified.

Available arguments:

  • name

  • type

  • default

  • desc

  • regex

  • in

Nested Parameters


Use a keyword group to define a group of parameters which is enclosed to the parent HashRef parameter.

        requires('name', type => HashRef, group {
            requires('first_name', type => Str),
            requires('last_name', type => Str),


Use ArrayRef[*] types from your compatible type library to define arrays.

    requires('list', type => ArrayRef[Int], desc => 'List of integers')


Raisin supports Moo(se)-compatible type constraint so you can use any of the Moose, Moo or Type::Tiny type constraints.

By default Raisin depends on Type::Tiny and it's Types::Standard type contraint library.

You can create your own types as well. See Type::Tiny::Manual and Moose::Manual::Types.


Those blocks can be executed before or/and after every API call, using before, after, before_validation and after_validation.

Callbacks execute in the following order:

  • before

  • before_validation

  • after_validation

  • after

The block applies to every API call

    before sub {
        my $self = shift;
        say $self->req->method . "\t" . $self->req->path;

    after_validation sub {
        my $self = shift;
        say $self->res->body;

Steps after_validation and after are executed only if validation succeeds.

Every callback has only one argument as an input parameter which is Raisin object. For more information of available methods see "CONTROLLER" in Raisin.


By default, Raisin supports YAML, JSON, and TEXT content types. Default format is YAML.

Response format can be determined by Accept header or route extension.

Serialization takes place automatically. So, you do not have to call encode_json in each JSON API implementation.

The response format (and thus the automatic serialization) is determined in the following order:

  • Use the file extension, if specified. If the file is .json, choose the JSON format.

  • Attempt to find an acceptable format from the Accept header.

  • Use the default format, if specified by the default_format option.

  • Default to YAML.

Your API can declare to support only one serializator by using "api_format" in Raisin.

Custom formatters for existing and additional types can be defined with a Raisin::Encoder/Raisin::Decoder.


Call JSON::encode_json and JSON::decode_json.


Call YAML::Dump and YAML::Load.


Call Data::Dumper->Dump if output data is not a string.

The order for choosing the format is the following.

  • Use the route extension.

  • Use the value of the Accept header.

  • Fallback to default.


Raisin has a built-in logger and supports for Log::Dispatch. You can enable it by:

    plugin 'Logger', outputs => [['Screen', min_level => 'debug']];

Or use Raisin::Logger with a fallback option:

    plugin 'Logger', fallback => 1;

The plugin registers a log subroutine to Raisin. Below are examples of how to use it.

    app->log(debug => 'Debug!');
    app->log(warn => 'Warn!');
    app->log(error => 'Error!');

app is a Raisin instance, so you can use $self instead of app where it is possible.

See Raisin::Plugin::Logger.


Raisin script

You can see application routes with the following command:

    $ raisin examples/pod-synopsis-app/
    GET     /user
    GET     /user/all
    POST    /user
    GET     /user/:id
    DELETE  /user/:id
    PUT     /user/:id
    GET     /echo

Including parameters:

    $ raisin --params examples/pod-synopsis-app/
    GET     /user
       start Int{0}
       count Int{10}
    GET     /user/all
    POST    /user
      *name     Str
      *password Str
    email    Str
    GET     /user/:id
      *id Int
    DELETE  /user/:id
      *id Int
    PUT     /user/:id
      *id Int
    GET     /echo
      *data Any{ёй}


Swagger compatible API documentations.

    plugin 'Swagger';

Documentation will be available on http://<url>/swagger.json URL. So you can use this URL in Swagger UI.

See Raisin::Plugin::Swagger.


You can easily add any Plack middleware to your application using middleware keyword. See "middleware" in Raisin.


Raisin can be extended using custom modules. Each new module must be a subclass of the Raisin::Plugin namespace. Modules' job is to initialize and register new methods into the web application class.

For more see "plugin" in Raisin and Raisin::Plugin.


See Plack::Test, Test::More and etc.

    my $app = Plack::Util::load_psgi("$Bin/../script/");

    test_psgi $app, sub {
        my $cb  = shift;
        my $res = $cb->(GET '/user');

        subtest 'GET /user' => sub {
            if (!is $res->code, 200) {
                diag $res->content;
                BAIL_OUT 'FAILED!';
            my $got = Load($res->content);
            isdeeply $got, $expected, 'Data!';


Deploying a Raisin application is done the same way any other Plack application is deployed:

    $ plackup -E deployment -s Starman app.psgi


    use Plack::Builder;
    use RaisinApp;
    use KelpApp;

    builder {
        mount '/' => KelpApp->new->run;
        mount '/api/rest' => RaisinApp->new;


    use Plack::Builder;
    use Dancer ':syntax';
    use Dancer::Handler;
    use RaisinApp;

    my $dancer = sub {
        setting appdir => '/home/dotcloud/current';
        load_app 'My::App';
        my $env = shift;
        my $req = Dancer::Request->new(env => $env);

    builder {
        mount '/' => $dancer;
        mount '/api/rest' => RaisinApp->new;


    use Plack::Builder;
    use RaisinApp;

    builder {
        mount '/' => builder {
            enable 'Deflater';
            require '';

        mount '/api/rest' => RaisinApp->new;

See also Plack::Builder, Plack::App::URLMap.


Raisin comes with three instance in example directory:


Basic example.


Shows the possibility of using "present" in Raisin with DBIx::Class and Rose::DB::Object.


Shows an example of complex application.


  • Versioning support;

  • Mount API's in any place of resource block;



This module was inspired both by Grape and Kelp, which was inspired by Dancer, which in its turn was inspired by Sinatra.


Artur Khabibullin


This software is copyright (c) 2019 by Artur Khabibullin.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.