How to Load Service Configuration inside a Bundle

In Symfony, you’ll find yourself using many services. These services can be registered in the app/config directory of your application. But when you want to decouple the bundle for use in other projects, you want to include the service configuration in the bundle itself. This article will teach you how to do that.

Creating an Extension Class

In order to load service configuration, you have to create a Dependency Injection Extension for your bundle. This class has some conventions in order to be detected automatically. But you’ll later see how you can change it to your own preferences. By default, the Extension has to comply with the following conventions:

• It has to live in the DependencyInjection namespace of the bundle;
• The name is equal to the bundle name with the Bundle suffix replaced by Extension (e.g. the Extension class of the AppBundle would be called AppExtension and the one for AcmeHelloBundle would be called AcmeHelloExtension).

The Extension class should implement the ExtensionInterface, but usually you would simply extend the Extension class:

// src/Acme/HelloBundle/DependencyInjection/AcmeHelloExtension.php
namespace Acme\HelloBundle\DependencyInjection;

use Symfony\Component\HttpKernel\DependencyInjection\Extension;
use Symfony\Component\DependencyInjection\ContainerBuilder;

class AcmeHelloExtension extends Extension
{
    public function load(array $configs, ContainerBuilder $container)
    {
        // ... you'll load the files here later
    }
}

Manually Registering an Extension Class

When not following the conventions, you will have to manually register your extension. To do this, you should override the Bundle::getContainerExtension() method to return the instance of the extension:

// ...
use Acme\HelloBundle\DependencyInjection\UnconventionalExtensionClass;

class AcmeHelloBundle extends Bundle
{
    public function getContainerExtension()
    {
        return new UnconventionalExtensionClass();
    }
}

Since the new Extension class name doesn’t follow the naming conventions, you should also override Extension::getAlias() to return the correct DI alias. The DI alias is the name used to refer to the bundle in the container (e.g. in the app/config/config.yml file). By default, this is done by removing the Extension prefix and converting the class name to underscores (e.g. AcmeHelloExtension‘s DI alias is acme_hello).

Using the load() Method

In the load() method, all services and parameters related to this extension will be loaded. This method doesn’t get the actual container instance, but a copy. This container only has the parameters from the actual container. After loading the services and parameters, the copy will be merged into the actual container, to ensure all services and parameters are also added to the actual container.

In the load() method, you can use PHP code to register service definitions, but it is more common if you put these definitions in a configuration file (using the Yaml, XML or PHP format). Luckily, you can use the file loaders in the extension!

For instance, assume you have a file called services.xml in the Resources/config directory of your bundle, your load method looks like:

use Symfony\Component\DependencyInjection\Loader\XmlFileLoader;
use Symfony\Component\Config\FileLocator;

// ...
public function load(array $configs, ContainerBuilder $container)
{
    $loader = new XmlFileLoader(
        $container,
        new FileLocator(__DIR__.'/../Resources/config')
    );
    $loader->load('services.xml');
}

Other available loaders are the YamlFileLoader, PhpFileLoader and IniFileLoader.

注解

The IniFileLoader can only be used to load parameters and it can only load them as strings.

Using Configuration to Change the Services

The Extension is also the class that handles the configuration for that particular bundle (e.g. the configuration in app/config/config.yml). To read more about it, see the “How to Create Friendly Configuration for a Bundle” article.