Laravel: Difference Between Route Middleware and Policy

Question

Developing an app with laravel I realised that what can be done with Policy can exactly be done with Middleware. Say I want to prevent a user from updating a route if he/she is not the owner of the information, I can easily check from the route and can do the same from the policy.

So my question is why should I use policy over middleware and vice versa

Solution 1

I'm currently going through a small refactor with my roles, permissions and routes and asked myself the same question.

At the surface level, it appears true middleware and policies perform the same general idea. Check if a user can do what they are doing.

For reference here's the laravel docs...

Middleware "May I see this? May I go here?"

HTTP middleware provide a convenient mechanism for filtering HTTP requests entering your application. For example, Laravel includes a middleware that verifies the user of your application is authenticated. If the user is not authenticated, the middleware will redirect the user to the login screen. However, if the user is authenticated, the middleware will allow the request to proceed further into the application.

Of course, additional middleware can be written to perform a variety of tasks besides authentication. A CORS middleware might be responsible for adding the proper headers to all responses leaving your application. A logging middleware might log all incoming requests to your application.

https://laravel.com/docs/master/middleware#introduction

In my reading, Middleware is about operating at the request level. In the terms of "Can this user see a page?", or "Can this user do something here?"

If so, it goes to the controller method associated with that page. Interestingly enough, Middleware may say, "Yes you may go there, but I'll write down that you are going." Etc.

Once it's done. It has no more control or say in what the user is doing. Another way I think of it as the middleperson.

Policies "Can I do this? Can I change this?"

In addition to providing authentication services out of the box, Laravel also provides a simple way to organize authorization logic and control access to resources. There are a variety of methods and helpers to assist you in organizing your authorization logic, and we'll cover each of them in this document.

https://laravel.com/docs/master/authorization#introduction

Policies however, appear to be more concerned with doing. Can the user update any entry, or only theirs?

These questions seem fit for a controller method where all the calls to action on a resource are organized. Retrieve this object, store or update the article.

As tjbb mentioned, middleware can make routes very messy and hard to manage. This is an example from my routes file:

The problem

    Route::group(['middleware' =>'role:person_type,person_type2',], function () {
        Route::get('download-thing/{thing}', [
             'as' => 'download-thing', 
             'uses' => 'ThingController@download'
        ]);
    }); 

This gets very hard to read in my route file!

Another approach with policies

//ThingController
public function download(Thing $thing)
{
    //Policy method and controller method match, no need to name it
    $this->authorize($thing);

    //download logic here....
}

Solution 2

Route middleware allows you to apply request handling to a large range of routes, instead of repeating the code in every controller action - checking authentication and redirecting guests is a good example. Controllers instead contain logic unique to specific routes/actions - you could use middleware for this, but you'd need separate middleware for every route's logic and it would all get very messy.

Policies/abilities are simply a way of checking user permissions - you can query them from a controller, or from middleware, or anywhere else. They only return true or false, so they aren't equivalent to controllers or middleware. Most of the time abilities will be comparing a user to another model, which will have been loaded based on an identifier sent to a controller action, but there are probably some applications for use with middleware too.