Defining a controller to provide a custom page

Whenever an HTTP request is made to a Drupal site, the path for the URL is routed to a controller. Controllers are responsible for returning the response for a path that has been defined as a route. Generally, these controllers return render arrays for Drupal’s render system to convert into HTML.

In this recipe, we will define a controller that returns a render array to display a message on the page.

How to do it…

1. First, we need to create the src/Controller directory in the module’s directory. We will put our controller class in this directory, which gives our controller class the Controller namespace:

   mkdir -p src/Controller

2. Create a file named HelloWorldController.php in the controller directory. This will hold our HelloWorldController controller class.
3. Our HelloWorldController class will extend the ControllerBase base class provided by Drupal core:

   <?php

   namespace Drupal\mymodule\Controller...