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WebfactoryHttpCacheBundle is a Symfony bundle that features a more powerful HTTP cache validation via the last modified header than the #[Cache] attribute contained in the symfony/http-kernel package.

The #[ReplaceWithNotModifiedResponse] attribute lets you write small LastModifiedDeterminators for each one of the underlying resources of the requested page. They can be reused and combined freely and can even be defined as services.

Consider this controller code:

<?php

// ...
use Webfactory\HttpCacheBundle\NotModified\Attribute\ReplaceWithNotModifiedResponse;

class MyController {
    // Routing etc. configuration skipped for brevity
     
    #[ReplaceWithNotModifiedResponse(["@app_caching_post", "@app_caching_latest_posts"])]
    public function indexAction(Post $post): Response
    {
        // your code
        // won't be called in case of a 304
    }
}

When Symfony's routing has chosen this controller action, all of the LastModifiedDeterminators are called to return their respective last modified date.

In this case, both LastModifiedDeterminators are configured as services: @app_caching_post and @app_caching_latest_posts. The first one returns the update date of the requests $post, the second one may use the PostRepository injected from the DI container to return the last update date of the x latest posts.

#[ReplaceWithNotModifiedResponse] combines all of the LastModifiedDeterminators dates to determine to last modified date of the overall page. Finally, if the request contains an appropriate if-not-modified-since header, the execution of the controller action will be skipped and an empty response with a "304 Not Modified" status code will be sent. If your LastModifiedDeterminators are fast, this can improve your performance greatly.

What we like about the LastModifiedDeterminators is that they encourage to separate the concerns nicely and encapsulate the tasks into small units that are easy to understand, reusable and unit test.

Note: #[ReplaceWithNotModifiedResponse] does not alter or add Cache-Control header settings. So, by default your response will remain private and end up in browser caches only. If you want it to be kept in surrogate caches (like Varnish or the Symfony Http Cache), you can add #[Cache(smaxage: 0)]. This will make the response public, but also requires a revalidation on every request as the response is always considered stale. Learn more about Symonfy's HTTP caching.

Usage

Choose a controller action you want to possibly replace with a 304 Not Modified response. Write one LastModifiedDeterminator for each of the different underlying resources, implementing the Webfactory\HttpCacheBundle\NotModified\LastModifiedDeterminator interface.

<?php
// src/Caching/PostsLastModifiedDeterminator.php
namespace App\Caching;

use App\Entity\PostRepository;
use Symfony\Component\HttpFoundation\Request;
use Webfactory\HttpCacheBundle\NotModified\LastModifiedDeterminator;

/**
 * Returns the publishing date of the latest posts.
 */
final class PostsLastModifiedDeterminator implements LastModifiedDeterminator
{
    public function __construct(
        private readonly BlogPostRepository $blogPostRepository,
    ) {
    
    public function getLastModified(Request $request): ?\DateTime
    {
        $post = $this->blogPostRepository->findLatest();
        
        return $post?->getPublishingDate();
    }
}

You can use the $request in the getLastModified e.g. to get route parameters, which is necessary e.g. if you have some filters coded in the requested URL.

If your LastModifiedDeterminator has dependencies you'd like to be injected, configure it as a service.

Then, add the #[ReplaceWithNotModifiedResponse] attribute to the chosen controller method and parameterize it with your LastModifiedDeterminators:

<?php

namespace src\Controller;

use Symfony\Component\HttpFoundation\Response;
use Webfactory\HttpCacheBundle\NotModified\Attribute\ReplaceWithNotModifiedResponse;

final class MyController
{
     #[ReplaceWithNotModifiedResponse([...])]
    public function indexAction()
    {
        // ...
        return new Response(...);
    }
}

The most simple form of adding a LastModifiedDeterminator is passing its fully qualfified class name:

#[ReplaceWithNotModifiedResponse([\App\Caching\MySimpleLastModifiedDeterminator::class])]

If your LastModifiedDeterminator needs simple constructor arguments, you can pass them in array form:

#[ReplaceWithNotModifiedResponse([\App\Caching\MyLastModifiedDeterminator::class => ["key1" => 1, "key2" => ["*"]]])]

This would pass the array ['key1' => 1, 'key2' => ['*']] as an argument to MyLastModifiedDeterminator's constructor.

If your LastModifiedDeterminator has more sophisticated dependencies, you can define the LastModifiedDeterminator as a service, e.g.:

yaml // services.yml services: app_caching_latest_posts: class: App\Caching\PostsLastModifiedDeterminator arguments: - @repository_post

and put the service name into the attribute:

#[ReplaceWithNotModifiedResponse(["@app_caching_latest_posts"])]

To combine multiple LastModifiedDeterminators, simply add all of them to the attribute:

#[ReplaceWithNotModifiedResponse([
    "@app_caching_latest_posts",
    \App\Caching\MySimpleLastModifiedDeterminator::class,
    [\App\Caching\MyLastModifiedDeterminator::class => ["key1" = 1, "key2" => ["*"]]
])]

The latest last modified date determines the last modified date of the response.

Credits, Copyright and License

This bundle was started at webfactory GmbH, Bonn.

webfactory / http-cache-bundle

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Credits, Copyright and License