Framework Documentation - Preload Package

Overview

The Preload package provides a set of utility classes for managing HTTP/2 preload relations.

Usage

The Joomla\Preload\PreloadManager class is used to assemble the data to build a "Link" header to include in your application's response with all HTTP/2 related resources and their relations (actions to be taken).

The Joomla\Preload\EventListener\PreloadSubscriber class is used to register an event listener for any Joomla\Application\AbstractWebApplication to attach this "Link" header to your response.

The Joomla\Preload\Service\PreloadProvider class is used to integrate these classes into your application's dependency injection container when using Joomla\DI\Container.

Example Integration

The below example assumes you are using Twig in your application, have registered the PreloadProvider to your dependency injection container to expose the manager service and send the "Link" header, and you want to specify your CSS or JavaScript resources have a HTTP/2 relation on them.

<link href="{{ http2_link('media/css/app.css', 'preload', {'as' => 'stylesheet'}) }}" rel="stylesheet">
<script src="{{ http2_link('media/js/app.js', 'preload', {'as' => 'script'}) }}"></script>

use Joomla\Preload\PreloadManager;
use Twig\Extension\AbstractExtension;
use Twig\TwigFunction;

final class PreloadExtension extends AbstractExtension
{
	private $preloadManager;
	
	public function __construct(PreloadManager $preloadManager)
	{
		$this->preloadManager = $preloadManager;
	}
	
	public function getFunctions()
	{
		return [
			new TwigFunction('http2_link', [$this, 'linkAsset']),
		];
	}
	
	/**
	 * Preload a resource
	 *
	 * @param   string  $uri         The URI for the resource to preload
	 * @param   string  $linkType    The preload method(s) to apply
	 * @param   array   $attributes  The attributes of this link (e.g. "array('as' => true)", "array('pr' => 0.5)")
	 *
	 * @return  string  The resource URI, useful for chaining this function with another Twig function in your template
	 */
	public function linkAsset(string $uri, string $linkType = 'preload', array $attributes = []): string
	{
		$this->preloadManager->link($uri, $linkType, $attributes);

		return $uri;
	}