Erlang REST framework


Simplistic REST framework that runs on top of mochiweb.


  • Routes Composable routing system that supports GET POST PUT and DELETE http verbs.
  • Middleware : Functions that have access to the request and the response, intercepting routes before and/or after execution.
  • Basic Authentication : Authentication module that can be easily integrated with Middleware.
  • HTTPS Support


  1. Download and install rebar3

  2. Create a new application using rebar

  3. Edit the file rebar.config and add the following lines inside deps:

{deps, [ {rooster, ".*", {git, "git://", {branch, "master"}}} ]}.

  1. Compile and download dependencies with rebar3 compile

Quick start

Create an entry file that will be the initialization module of your application:


start() ->
  rooster:start(#{port => 8080},
                #{routes => [hello()]}).

hello() ->
  {'GET', "/hello", fun(_) -> #{message => <>} end}.

Start it using the command:

  -pa ebin _build/default/lib/*/ebin 
  -boot start_sasl 
  -s server 
  -s reloader

Run curl localhost:8080/hello and it should return:

{"message": "hello world"}


Given the following functions, you will find how to define routes using generic or nested definition.


% custom header
get_products(_Req) ->
  {200, [#{..}, #{..}], [{"custom-header", "foo"}]}.

% request path param
get_product(#{params := params}) ->
  Id = maps:get(id, params),
  {200, #{id => Id, price => 8000}}.

% request payload
save_product(#{body := Body}) ->
  {201, Body}.

Is important to note that the function must have one parameter, that will contain the request information.

Generic definition

The simplest way of defining routes.

exports() ->
  [{'GET', "/products", fun get_products/1, [auth]},
   {'POST', "/products", fun save_product/1, [auth, admin]}
   {'GET', "/products/:id", fun get_product/1, [auth]}].

The exports method will provide the list of available endpoints that this module contains. Each tuple should have {HTTP verb, route path, route handler, list of middleware} , the list of middleware is not a required parameter as a specific route may use none.

Nested definition

For routes that gonna share a specific root path and or middleware, declaring routes in a nested way should be the proper solution.

exports() ->
  [{"/products", [auth],
    [{'GET', fun get_products/1},
     {'POST', fun save_product/1, [admin]}
     {'GET', "/:id", fun get_product/1}]}].

The nested definition should fit on the specification:

{root path, list of middleware,
   [{HTTP verb, *nested path*, route handler, *list of middleware*}]}

Ps: The parameters surround by * are not required.


The request that will be passed to the route handlers is a map as the one bellow:

#{path          => ...,
  method        => ...,
  headers       => ...,
  body          => ...,
  qs            => ...,
  params        => ...,
  cookies       => ...,
  authorization => ...}


The middleware map can have both leave and enter keys. The enter function will have access to the request information and will be able to change it, the leave function will have access to the response and will be able to change it as well. At any moment that a middleware returns {break, {status, response}} the chain of execution will terminate and the response will be evaluated as the request result.


Simple example using a middleware that intercepts the route handler response and add to it custom headers.


access_control() ->
  [{"access-control-allow-methods", "*"},
   {"access-control-allow-headers", "*"},
   {"access-control-allow-origin", "*"}].

cors() ->
  #{name  => cors,
    leave => fun({Status, Resp, Headers}) -> {Status, Resp, Headers ++ access_control()} end}.

Basic authentication

Intercepts the http request before the route handler executes and returns 403 if credentials do not match.


basic_auth(#{authorization := Auth} = Req) ->
  Authorizated = rooster_basic_auth:is_authorized(Auth, {"admin", "admin"}),
  case Authorizated of
    true ->
    _ ->
      {break, {403, #{reason => <>}}}

auth() ->
  #{name => auth,
    enter => fun basic_auth/1}.


After generating the SSL certificate for your domain, everything that needs to be done is to pass some extra parameters for the server configuration map: ( ssl and ssl_opts ).

#{port     => 8080,
  ssl      => {ssl, true},
  ssl_opts => {ssl_opts, [{certfile, "{PATH}/server_cert.pem"},
                          {keyfile, "{PATH}/server_key.pem"}]}}


  • mochiweb: HTTP server
  • jsx: JSON parser



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