上次说了provider，那么这次来说说facade
首先是启动的源头，从laravel的kernel类中的$bootstrappers 数组，我们可以看到它的一些系统引导方法，其中的RegisterFacades便是用来注册facade门面类的了。
protected $bootstrappers = [
\Illuminate\Foundation\Bootstrap\LoadEnvironmentVariables::class,
\Illuminate\Foundation\Bootstrap\LoadConfiguration::class,
\Illuminate\Foundation\Bootstrap\HandleExceptions::class,
\Illuminate\Foundation\Bootstrap\RegisterFacades::class,
\Illuminate\Foundation\Bootstrap\RegisterProviders::class,
\Illuminate\Foundation\Bootstrap\BootProviders::class,
];
同样是有一个register类，通过这个类进行别名等注册操作
namespace Illuminate\Foundation\Bootstrap; use Illuminate\Foundation\AliasLoader;
use Illuminate\Support\Facades\Facade;
use Illuminate\Foundation\PackageManifest;
use Illuminate\Contracts\Foundation\Application; class RegisterFacades
{
/**
* Bootstrap the given application.
*
* @param \Illuminate\Contracts\Foundation\Application $app
* @return void
*/
public function bootstrap(Application $app)
{
//清除facade所有已绑定实例
Facade::clearResolvedInstances();
//将app存入对象
Facade::setFacadeApplication($app);
//将这些别名数组通过构造函数存入对象中
AliasLoader::getInstance(array_merge(
//通过Illuminate\Config\Repository获取config/app.php中的aliases数组
$app->make('config')->get('app.aliases', []),
//还记得最开始的博文中提到的那个包清单吗，这里也从中获取了它的aliases
$app->make(PackageManifest::class)->aliases()
//通过spl_autoload_register函数注册另一种自动加载函数
))->register();
}
}
public static function getInstance(array $aliases = [])
{
//注册时的实例是空的，会通过构造方法把刚刚传入的别名数组存入对象
if (is_null(static::$instance)) {
return static::$instance = new static($aliases);
} $aliases = array_merge(static::$instance->getAliases(), $aliases); static::$instance->setAliases($aliases); return static::$instance;
} private function __construct($aliases)
{
$this->aliases = $aliases;
}
public function register()
{
if (! $this->registered) {
$this->prependToLoaderStack(); $this->registered = true;
}
} /**
* Prepend the load method to the auto-loader stack.
*
* @return void
*/
protected function prependToLoaderStack()
{
//最后通过自动加载函数将本对象中的load方法放入自动加载队列的前端，在我们通过类名调用方法时，会触发自动加载函数队列，会优先触发这个函数，查找到对应文件的路径然后加载相应文件
spl_autoload_register([$this, 'load'], true, true);
}
public function load($alias)
{
//若传入的命名空间不为当前facade数组内才会通过这个方法加载
if (static::$facadeNamespace && strpos($alias, static::$facadeNamespace) === 0) {
$this->loadFacade($alias); return true;
}
//否则直接返回其别名
if (isset($this->aliases[$alias])) {
return class_alias($this->aliases[$alias], $alias);
}
} /**
* Load a real-time facade for the given alias.
*
* @param string $alias
* @return void
*/
protected function loadFacade($alias)
{
require $this->ensureFacadeExists($alias);
} /**
* Ensure that the given alias has an existing real-time facade class.
*
* @param string $alias
* @return string
*/
protected function ensureFacadeExists($alias)
{
//从缓存中返回路径
if (file_exists($path = storage_path('framework/cache/facade-'.sha1($alias).'.php'))) {
return $path;
} file_put_contents($path, $this->formatFacadeStub(
$alias, file_get_contents(__DIR__.'/stubs/facade.stub')
)); return $path;
}
由于laravel中composer的执行过程过于繁琐，这里就不做深究了。原理是一样的，通过别名找到命名空间的类名，再由composer的类名与文件路径映射关系，自动加载函数找到相应文件加载进来。
那么我们来自定义一个门面类试一下
1、新建一个facade类，这里返回的test是上一篇博客中定义的对象
namespace App\Facades; use Illuminate\Support\Facades\Facade; class Test extends Facade
{
protected static function getFacadeAccessor()
{
return 'App\Contracts\Test';
}
}
2、将它添加到config/app.php的aliases别名数组中
'aliases' => [
'App' => Illuminate\Support\Facades\App::class,
'Artisan' => Illuminate\Support\Facades\Artisan::class,
'Auth' => Illuminate\Support\Facades\Auth::class,
'Blade' => Illuminate\Support\Facades\Blade::class,
'Broadcast' => Illuminate\Support\Facades\Broadcast::class,
'Bus' => Illuminate\Support\Facades\Bus::class,
'Cache' => Illuminate\Support\Facades\Cache::class,
'Config' => Illuminate\Support\Facades\Config::class,
'Cookie' => Illuminate\Support\Facades\Cookie::class,
'Crypt' => Illuminate\Support\Facades\Crypt::class,
'DB' => Illuminate\Support\Facades\DB::class,
'Eloquent' => Illuminate\Database\Eloquent\Model::class,
'Event' => Illuminate\Support\Facades\Event::class,
'File' => Illuminate\Support\Facades\File::class,
'Gate' => Illuminate\Support\Facades\Gate::class,
'Hash' => Illuminate\Support\Facades\Hash::class,
'Lang' => Illuminate\Support\Facades\Lang::class,
'Log' => Illuminate\Support\Facades\Log::class,
'Mail' => Illuminate\Support\Facades\Mail::class,
'Notification' => Illuminate\Support\Facades\Notification::class,
'Password' => Illuminate\Support\Facades\Password::class,
'Queue' => Illuminate\Support\Facades\Queue::class,
'Redirect' => Illuminate\Support\Facades\Redirect::class,
'Redis' => Illuminate\Support\Facades\Redis::class,
'Request' => Illuminate\Support\Facades\Request::class,
'Response' => Illuminate\Support\Facades\Response::class,
'Route' => Illuminate\Support\Facades\Route::class,
'Schema' => Illuminate\Support\Facades\Schema::class,
'Session' => Illuminate\Support\Facades\Session::class,
'Storage' => Illuminate\Support\Facades\Storage::class,
'URL' => Illuminate\Support\Facades\URL::class,
'Validator' => Illuminate\Support\Facades\Validator::class,
'View' => Illuminate\Support\Facades\View::class,
//刚刚新建的facades
'Test' => \App\Facades\Test::class,
],3、在路由文件中调用它
Route::any('/index', function (){
Test::doing();
});我们会发现，即使我们没有通过app对象进行make也没有任何命名空间的引入，它就这样被调用了。
如果是在类中调用，那么就要麻烦一些了，需要ues这个别名，注意这一点
namespace App\Http\Controllers; use Illuminate\Http\Request;
//use App\Contracts\Test;
//注意这里只引入了别名，由于命名空间冲突，所以我注释了其他部分
use Test; class IndexController extends Controller
{
// public function __construct(Test $test)
// {
// $this->test = $test;
// } public function index(Test $test)
{
Test::doing();
// app()->make('App\Contracts\Test')->doing();
// echo '<br>';
//
// //只有通过构造方法进行自动加载依赖的方式才能触发契约的when绑定
// $this->test->doing();
//
// echo '<br>';
// //因为laravel中的上下文绑定只能具体到类，所以这里的$test实例依然为普通绑定
// $test->doing(); }
}
通过这个demo的实践，facade还是比较简单的。