Accessing the Component Router class

If you're not familiar with Joomla Dependency Injection and Extension classes then you may find it useful to read Extension and Dispatcher Classes and Dependency Injection before tackling this section. Since Joomla 4 the preferred way to access the component router class is by using a RouterFactory class which is injected as a dependency to the component. This means that in the component's services/provider.php file we have (eg in administrator/components/com_content/services/provider.php):

use Joomla\CMS\Extension\Service\Provider\RouterFactory;
...
public function register(Container $container)
{
    ...
    $container->registerServiceProvider(new RouterFactory('\\Joomla\\Component\\Content'));

    $container->set(
        ComponentInterface::class,
        function (Container $container) {
            $component = new ContentComponent(,,,));
            ...
            $component->setRouterFactory($container->get(RouterFactoryInterface::class));

            return $component;
        }
    );
}

Note that here the RouterFactory refers to the class Joomla\CMS\Extension\Service\Provider\RouterFactory which is in libraries/src/Extension/Service/Provider/RouterFactory.php.

The line:

$container->registerServiceProvider(new RouterFactory('\\Joomla\\Component\\Content'));

basically creates an instance of this class, passing in the namespace to use, and calls register() on the class instance:

public function register(Container $container)
{
    $container->set(
        RouterFactoryInterface::class,
        function (Container $container) {
            $categoryFactory = null;

            if ($container->has(CategoryFactoryInterface::class)) {
                $categoryFactory = $container->get(CategoryFactoryInterface::class);
            }

            return new \Joomla\CMS\Component\Router\RouterFactory(
                $this->namespace,
                $categoryFactory,
                $container->get(DatabaseInterface::class)
            );
        }
    );
}

This results in another entry in the Dependency Injection Container (DIC), keyed by RouterFactoryInterface::class (which is just a string of the fully qualified name of that class).

When the com_content component is instantiated Joomla gets it out of the DIC and then these lines are run:

function (Container $container) {
    $component = new ContentComponent(,,,));
    ...
    $component->setRouterFactory($container->get(RouterFactoryInterface::class));

    return $component;
}

The ContentComponent is instantiated - this is the com_content Extension class which is in administrator/components/com_content/src/Extension/ContentComponent.php. If you have a look at the code in that file, then you'll see:

// outside the class definition
use Joomla\CMS\Component\Router\RouterServiceTrait;

class ContentComponent extends MVCComponent implements
  ...
// inside the class definition
use RouterServiceTrait;

(The PHP use statement has different meanings depending upon whether it's used inside or outside a class.) This RouterServiceTrait in libraries/src/Component/Router/RouterServiceTrait.php has 2 key functions, which through this use statement become methods of the com_content Extension class:

1. setRouterFactory - this is immediately used in the line:

$component->setRouterFactory($container->get(RouterFactoryInterface::class));

which also gets the RouterFactoryInterface::class entry out of the DIC. Referring back to the code in libraries/src/Extension/Service/Provider/RouterFactory.php you can see that getting the entry out of the DIC will result in a new \Joomla\CMS\Component\Router\RouterFactory - this now is the genuine RouterFactory class. The setRouterFactory call now stores this instance locally within the com_content Extension as $this->routerFactory.

2. createRouter - this function is called when Joomla wants to get the com_content component router. As you can see from the RouterServiceTrait code, this retrieves the stored routerFactory and calls createRouter on it:

return $this->routerFactory->createRouter($application, $menu);

(As you can see, there are 2 createRouter functions in different classes here!)

This will result in the createRouter function of the genuine RouterFactory being called. The code is in libraries/src/Component/Router/RouterFactory.php:

public function createRouter(CMSApplicationInterface $application, AbstractMenu $menu): RouterInterface
{
    $className = trim($this->namespace, '\\') . '\\' . ucfirst($application->getName()) . '\\Service\\Router';

    if (!class_exists($className)) {
        throw new \RuntimeException('No router available for this application.');
    }

    return new $className($application, $menu, $this->categoryFactory, $this->db);
}

This forms the classname from :

• the stored namespace (for com_content this is '\\Joomla\\Component\\Content', passed in the registerServiceProvider call within the com_content services/provider.php file)
• $application->getName() which when we're running on the Joomla site front-end returns "site".

The final class name for com_content is \Joomla\Component\Content\Site\Service\Router`, and from the PSR4 namespacing rules this is found in components/com_content/src/Service/Router.php.

You should follow this pattern whenever you have a component router for your own component.

Your Choice of Component Router

As described above, Joomla will expect to find your component router in the class \<Your namespace>\Site\Service\Router in the file components/com_yourcomponent/src/Service/Router.php, and will expect it to implement the interface Joomla\CMS\Component\Router\RouterInterface.

At this stage you have the choice of whether to use the traditional router with preprocess(), build() and parse() functions, or to use the RouterView option.

If you're using a traditional router then you will have to fill out the skeleton code below:

use Joomla\CMS\Component\Router\RouterInterface;
use Joomla\CMS\Categories\CategoryFactoryInterface;
use Joomla\Database\DatabaseInterface;
class Router implements RouterInterface
{
    public function __construct($application, $menu, CategoryFactoryInterface $categoryFactory, DatabaseInterface $db) {}
    public function build(&$query) {}
    public function parse(&$segments) {}
    public function preprocess($query) {}
}

If you're using the RouterView approach then your class extends Joomla\CMS\Component\Router\RouterView, and this latter class implements RouterInterface. You provide the RouterView configurations as described in RouterView Configurations.

Using the Site Router in the Joomla back-end

There may be occasions where you want to display on the administrator back-end the result of building a SEF URL which will be present on the site front-end. To enable this, Joomla provides the link() method within the Joomla\CMS\Router\Route class. It's basically the same as the Route::_() function, except that it has an additional parameter "client" at p1, which you would set to "site" to enable a site SEF URL to be built.

However to get this to work in your component you do need to do some extra work.

If you're using a traditional router with preprocess, build and parse functions then the only change you're probably going to have to make is how you obtain the set of site menuitems. When you're running the site application you can use:

$sitemenu = $app->getMenu();

However, if you're running the administrator application then you need to explicitly get the site menuitems, and load them:

use Joomla\CMS\Factory;
$app = Factory::getApplication();
$sitemenu = $app->getMenu('site');
$sitemenu->load();

as described in Menus and Menuitems. You only need to load them once.

If your component router uses RouterView then you need to ensure that the site menuitems are pre-loaded before you make the link() call. The SiteRouter code correctly looks for the site menuitems, even if you're running the functionality from the administrator back-end, but it doesn't perform a load(). You may find the routing doesn't work quite as expected; I'm not sure why this is - it may be because the routing algorithm takes into account the current site web page that the user is on (ie the "active" menuitem), which of course is not set if you're calling this functionality from the administrator back-end.