HTTP Middlewares

HTTP Middlewares allow you to put code that will run before or after. These might be used for authentication, logging, caching, request processing, and many other purposes. Note this interface replaces the SilverStripe 3 interface RequestFilter, which still works but is deprecated.

To create a middleware class, implement SilverStripe\Control\Middleware\HTTPMiddleware and define the process(HTTPRequest $request, callable $delegate) method. You can do anything you like in this method, but to continue normal execution, you should call $response = $delegate($request) at some point in this method.

In addition, you should return an HTTPResponse object. In normal cases, this should be the $response object returned by $delegate, perhaps with some modification. However, sometimes you will deliberately return a different response, e.g. an error response or a redirection.

app/code/CustomMiddleware.php

use SilverStripe\Control\Middleware\HTTPMiddleware;
use SilverStripe\Control\HTTPRequest;

class CustomMiddleware implements HTTPMiddleware
{
    public $Secret = 'SECRET';

    public function process(HTTPRequest $request, callable $delegate)
    {
        // You can break execution by not calling $delegate.
        if ($request->getHeader('X-Special-Header') !== $this->Secret) {
            return new HTTPResponse('You missed the special header', 400);
        }

        // You can modify the request before
        // For example, this might force JSON responses
        $request->addHeader('Accept', 'application/json');

        // If you want normal behaviour to occur, make sure you call $delegate($request)
        $response = $delegate($request);

        // You can modify the response after it has been generated
        $response->addHeader('X-Middleware-Applied', 'CustomMiddleware');

        // Don't forget to the return the response!
        return $response;
    }
}

Once you have created your middleware class, you must attach it to the Director config to make use of it.

Global middleware

By adding the service or class name to the Director.Middlewares property via injector, array, a middleware will be executed on every request:

app/_config/app.yml

---
Name: myrequestprocessors
After:
  - requestprocessors
---
SilverStripe\Core\Injector\Injector:
  SilverStripe\Control\Director:
    properties:
      Middlewares:
        CustomMiddleware: %$CustomMiddleware

Because these are service names, you can configure properties into a custom service if you would like:

app/_config/app.yml

SilverStripe\Core\Injector\Injector:
  SilverStripe\Control\Director:
    properties:
      Middlewares:
        CustomMiddleware: %$ConfiguredMiddleware
  ConfiguredMiddleware:
   class: 'CustomMiddleware'
   properties:
     Secret: "DIFFERENT-ONE"

Route-specific middleware

Alternatively, you can apply middlewares to a specific route. These will be processed after the global middlewares. You can do this by using the RequestHandlerMiddlewareAdapter class as a replacement for your controller, and register it as a service with a Middlewares property. The controller which does the work should be registered under the RequestHandler property.

app/_config/app.yml

SilverStripe\Core\Injector\Injector:
  SpecialRouteMiddleware:
    class: SilverStripe\Control\Middleware\RequestHandlerMiddlewareAdapter
    properties:
      RequestHandler: %$MyController
      Middlewares:
        - %$CustomMiddleware
        - %$AnotherMiddleware
SilverStripe\Control\Director:
  rules:
    special\section:
      Controller: %$SpecialRouteMiddleware

Application middleware

Some use cases will require a middleware to run before the Silverstripe CMS has been fully bootstrapped (e.g.: Updating the HTTPRequest before Silverstripe CMS routes it to a controller). This can be achieved by editing the Silverstripe CMS entry point file.

This file will be located in your own codebase at public/index.php, or directly in your project root at index.php if your project doesn't use the public web root. Find the line that instantiate HTTPApplication. Call the addMiddleware method on the HTTPApplication instance and pass it an instance of your middleware. This must be done before the request is handled.

// Default application
$kernel = new CoreKernel(BASE_PATH);
$app = new HTTPApplication($kernel);

$app->addMiddleware(new MyApplicationMiddleware());

$response = $app->handle($request);
$response->output();

Beware that by this point, the Silverstripe framework features you normally rely on won't be available in your middleware or in index.php because they won't have been initialised yet. (e.g.: ORM, Injector, services configured by Injector)

For example, Silverstripe's autoloading functionality won't work in index.php. So you might have to take additional steps to load your custom middleware class.

Configuring autoloading in your composer.json file is the best way to achieve this. Remember to call composer dump-autoload to regenerate your autoloader.

Alternatively, you can manually include the file containing your custom middleware with a require call. e.g.: require __DIR__.'/../app/src/MyApplicationMiddleware.php';

API Documentation