Corsica v1.1.3 Corsica.Router View Source

A router to handle and respond to CORS requests.

This module provides facilities for creating Plug.Router-based routers that handle CORS requests. A generated router will handle a CORS request by:

  • responding to it if it's a preflight request (refer to Corsica.send_preflight_resp/4 for more information) or
  • adding the right CORS headers to the Plug.Conn connection if it's a valid CORS request.

When a module calls use Corsica.Router, it can pass the same options that can be passed to the Corsica plug to the use call. Look at the documentation for the Corsica module for more information about these options.

CORS rules in a Corsica.Router can be defined through the resource/2 macro.


defmodule MyApp.CORS do
  use Corsica.Router,
    origins: ["", ""],
    allow_credentials: true,
    max_age: 600

  resource "/*"

  # We can override single settings as well.
  resource "/public/*", allow_credentials: false

Now in your application's endpoint:

defmodule MyApp.Endpoint do
  plug Plug.Head
  plug MyApp.CORS
  plug MyApp.Router

Note that a Corsica.Router router will always define a match-all route after the resource routes; this match-all route will simply return the connection unchanged, effectively continuing with the plug pipeline.

Link to this section Summary


Defines a CORS-enabled resource.

Link to this section Functions

Link to this macro

resource(route, opts \\ [])

View Source (macro)

Defines a CORS-enabled resource.

This macro takes advantage of the macros defined by Plug.Router (like options/3 and match/3) in order to define regular Plug.Router-like routes that efficiently match on the request url; the bodies of the autogenerated routes just perform a couple of checks before calling either Corsica.put_cors_simple_resp_headers/2 or Corsica.send_preflight_resp/4.

Note that if the request is a CORS preflight request (whether it's a valid one or not), a response is immediately sent to the client (whether the request is a valid one or not). This behaviour, combined with the definition of an additional OPTIONS route to route, makes Corsica.Router ideal to just put before any router in a plug pipeline, letting it handle preflight requests by itself.

The options given to resource/2 are merged with the default options like it happens with the rest of the functions in the Corsica module. The resource/2 macro also accepts the following options (similar to Plug.Router.match/3):

  • :host - the host which the route should match. Defaults to nil, meaning no host match, but can be a string like "" or a string ending with ., like "subdomain.", for a subdomain match.


resource "/foo", origins: "*"
resource "/wildcards/are/ok/*", max_age: 600
resource "/only/on/subdomain", host: "mysubdomain."