providers.md

Service Providers

• Introduction
• Basic Provider Example
• Registering Providers
• Deferred Providers

Introduction

Service providers are the central place of all Laravel application bootstrapping. Your own application, as well as all of Laravel's core services are bootstrapped via service providers.

But, what do we mean by "bootstrapped"? In general, we mean registering things, including registering service container bindings, event listeners, filters, and even routes. Service providers are the central place to configure your application.

If you open the config/app.php file included with Laravel, you will see a providers array. These are all of the service provider classes that will be loaded for your application. Of course, many of them are "deferred" providers, meaning they will not be loaded on every request, but only when the services they provide are actually needed.

In this overview you will learn how to write your own service providers and register them with your Laravel application.

Basic Provider Example

All service providers extend the Illuminate\Support\ServiceProvider class. This abstract class requires that you define at least one method on your provider: register. Within the register method, you should only bind things into the service container. You should never attempt to register any event listeners, routes, or any other piece of functionality within the register method.

The Artisan CLI can easily generate a new provider via the make:provider command:

php artisan make:provider RiakServiceProvider

The Register Method

Now, let's take a look at a basic service provider:

<?php namespace App\Providers;

use Riak\Connection;
use Illuminate\Support\ServiceProvider;

class RiakServiceProvider extends ServiceProvider {

	/**
	 * Register bindings in the container.
	 *
	 * @return void
	 */
	public function register()
	{
		$this->app->singleton('Riak\Contracts\Connection', function($app)
		{
			return new Connection($app['config']['riak']);
		});
	}

}

This service provider only defines a register method, and uses that method to define an implementation of Riak\Contracts\Connection in the service container. If you don't understand how the service container works, don't worry, we'll cover that soon.

This class is namespaced under App\Providers since that is the default location for service providers in Laravel. However, you are free to change this as you wish. Your service providers may be placed anywhere that Composer can autoload them.

The Boot Method

So, what if we need to register an event listener within our service provider? This should be done within the boot method. This method is called after all other service providers have been registered, meaning you have access to all other services that have been registered by the framework.

<?php namespace App\Providers;

use Event;
use Illuminate\Support\ServiceProvider;

class EventServiceProvider extends ServiceProvider {

	/**
	 * Perform post-registration booting of services.
	 *
	 * @return void
	 */
	public function boot()
	{
		Event::listen('SomeEvent', 'SomeEventHandler');
	}

	/**
	 * Register bindings in the container.
	 *
	 * @return void
	 */
	public function register()
	{
		//
	}

}

We are able to type-hint dependencies for our boot method. The service container will automatically inject any dependencies you need:

use Illuminate\Contracts\Events\Dispatcher;

public function boot(Dispatcher $events)
{
	$events->listen('SomeEvent', 'SomeEventHandler');
}

Registering Providers

All service providers are registered in the config/app.php configuration file. This file contains a providers array where you can list the names of your service providers. By default, a set of Laravel core service providers are listed in this array. These providers bootstrap the core Laravel components, such as the mailer, queue, cache, and others.

To register your provider, simply add it to the array:

'providers' => [
	// Other Service Providers

	'App\Providers\AppServiceProvider',
],

Deferred Providers

If your provider is only registering bindings in the service container, you may choose to defer its registration until one of the registered bindings is actually needed. Deferring the loading of such a provider will improve the performance of your application, since it is not loaded from the filesystem on every request.

To defer the loading of a provider, set the defer property to true and define a provides method. The provides method returns the service container bindings that the provider registers:

<?php namespace App\Providers;

use Riak\Connection;
use Illuminate\Support\ServiceProvider;

class RiakServiceProvider extends ServiceProvider {

	/**
	 * Indicates if loading of the provider is deferred.
	 *
	 * @var bool
	 */
	protected $defer = true;

	/**
	 * Register the service provider.
	 *
	 * @return void
	 */
	public function register()
	{
		$this->app->singleton('Riak\Contracts\Connection', function($app)
		{
			return new Connection($app['config']['riak']);
		});
	}

	/**
	 * Get the services provided by the provider.
	 *
	 * @return array
	 */
	public function provides()
	{
		return ['Riak\Contracts\Connection'];
	}

}

Laravel compiles and stores a list of all of the services supplied by deferred service providers, along with the name of its service provider class. Then, only when you attempt to resolve one of these services does Laravel load the service provider.