I want to do something when a node gets updated. To keep it simple, lets say display a drupal message.

**hello\_world.routing.yml**

```
hello_world:
    path: /node/{node}
    defaults:
        _controller: Drupal\hello_world\Controller\HelloWorldController::hello_world_entity_update
    requirements:
        _permission: 'access content'

```

Not sure if the path should be `/node/{node}/edit` instead.

**HelloWorldController.php**

```
<?php
/**
 * @file
 * Contains \Drupal\hello_world\Controller\HelloController.
 */

namespace Drupal\hello_world\Controller;

use Drupal\Core\Controller\ControllerBase;

class HelloWorldController extends ControllerBase {

  public function hello_world_entity_update(Drupal\Core\Entity\EntityInterface $entity) { 

    drupal_set_message(t('Something @var just happened.', array('@var' => 'cool')));  

  }
}

```

Since hook\_node\_update() was depreciated, I assume we now have to use hook\_entity\_update().

I am not getting the message upon updating a node, what I'm I missing or doing wrong?

---

### Update

> 
> Just so I don't confuse anyone.
> I was brainwashed into thinking I needed a routing file and a
> controller. All the D8 examples out there use them.
> 
> 
> **Since I was not creating any pages**,
> turns out **I did not need a routing.yml file nor a Controller.php file**
> nor the /src folder. All I had to do is approach this like Drupal 7,
> all that I needed was the .info.yml file and a .module file
> to put the hook.
> 
> 
>