Middlewares

Middleware is logic that is run before and after each request and is modeled after Django's Middleware system. It offers the following hooks:

beforeController: This is executed before a controller method is being executed. This allows you to plug additional checks or logic before that method, like for instance security checks
afterException: This is being run when either the beforeController method or the controller method itself is throwing an exception. The middleware is asked in reverse order to handle the exception and to return a response. If the middleware can't handle the exception, it throws the exception again
afterController: This is being run after a successful controller method call and allows the manipulation of a Response object. The middleware is run in reverse order
beforeOutput: This is being run after the response object has been rendered and allows the manipulation of the outputted text. The middleware is run in reverse order

To generate your own middleware, simply inherit from the Middleware class and overwrite the methods that should be used.

<?php

namespace OCA\MyApp\Middleware;

use \OCP\AppFramework\Middleware;


class CensorMiddleware extends Middleware {

    /**
     * this replaces "bad words" with "********" in the output
     */
    public function beforeOutput($controller, $methodName, $output): string {
        return str_replace('bad words', '********', $output);
    }

}

The middleware can be registered in the app's Application class:

Global Middlewares

Registered middleware will only intercept requests of the same app by default. To make a middleware global and trigger for other apps' middleware, add true as the second argument of the registerMiddleware call:

Dependency Injection Container Registration

Middleware can also be added using the registerMiddleware method of the container:

Parsing annotations

Sometimes it is useful to conditionally execute code before or after a controller method. This can be done by defining custom annotations. An example would be to add a custom authentication method or simply add an additional header to the response. To access the parsed annotations, inject the ControllerMethodReflector class:

<?php

namespace OCA\MyApp\Middleware;

use OCP\AppFramework\Middleware;
use OCP\AppFramework\Utility\IControllerMethodReflector;
use OCP\AppFramework\Http\Response;

class HeaderMiddleware extends Middleware {

  private $reflector;

  public function __construct(IControllerMethodReflector $reflector) {
      $this->reflector = $reflector;
  }

  /**
   * Add custom header if @MyHeader is used
   */
  public function afterController($controller, $methodName, Response $response): Response {
      if($this->reflector->hasAnnotation('MyHeader')) {
          $response->addHeader('My-Header', 3);
      }
      return $response;
  }
}