Facades 类别名设置流程 (class_alias)

mjczz 的个人博客 / 1434 / 0 / 创建于 5年前 / 更新于 5年前

Facade类别名设置

场景描述：

// web.php中
Route::get('/', function () {
    return view('welcome');
});

为何能直接使用Route,其实是调用了Illuminate\Support\Facades\Route类。然后通过facade获取对象执行对象方法（看我上一篇文章facade原理）
为何调用Route也就调用了Illuminate\Support\Facades\Route类，这就是这篇文章的核心：
class_alias：为一个类创建别名

核心代码类：Illuminate\Foundation\AliasLoader

public function load($alias)
    {
        if (static::$facadeNamespace && strpos($alias, static::$facadeNamespace) === 0) {
            $this->loadFacade($alias);

            return true;
        }

      // $alias来自于config/app.php中aliases数组中的一个键值队如：       
      // 'Route' => Illuminate\Support\Facades\Route::class 中的键“Route”
        if (isset($this->aliases[$alias])) {
            //'Route' => Illuminate\Support\Facades\Route::class,
            // class_alias:为一个类创建别名
            return class_alias($this->aliases[$alias], $alias);
        }
    }

具体流程如下：

入口文件index.php

// 此处才包含了设置facade类别名的操作
$response = $kernel->handle(
$request = Illuminate\Http\Request::capture()
);

进入Illuminate\Foundation\Http\Kernel类(Kernel.php)

/**
 * Handle an incoming HTTP request.
 *
 * @param  \Illuminate\Http\Request  $request
 * @return \Illuminate\Http\Response
 */
public function handle($request)
{
    try {
        $request->enableHttpMethodParameterOverride();
        // 进入这行
        $response = $this->sendRequestThroughRouter($request);
    } catch (Exception $e) {
        $this->reportException($e);

        $response = $this->renderException($request, $e);
    } catch (Throwable $e) {
        $this->reportException($e = new FatalThrowableError($e));

        $response = $this->renderException($request, $e);
    }

    $this->app['events']->dispatch(
        new Events\RequestHandled($request, $response)
    );

    return $response;
}

进入方法sendRequestThroughRouter

protected function sendRequestThroughRouter($request)
{
    // 将request对象绑定到容器$app的instances数组里面，实现单例模式
    $this->app->instance('request', $request);

    // 实际执行了这行 unset(static::$resolvedInstance["request"]);
    Facade::clearResolvedInstance('request');

    // 重点：这里的操作包含执行了Facade类的别名设置
    $this->bootstrap();

    return (new Pipeline($this->app))
                ->send($request)
                ->through($this->app->shouldSkipMiddleware() ? [] : $this->middleware)
                ->then($this->dispatchToRouter());
}

进入bootstrap方法

public function bootstrap()
{
    if (! $this->app->hasBeenBootstrapped()) {
        // 执行容器实例$app里面的bootstrapWith，携带参数是$this->bootstrappers()
        // $this->bootstrappers()最终返回的数组是Kernel实例的属性$bootstrappers
        // 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,
        // ];
        $this->app->bootstrapWith($this->bootstrappers());
    }
}

进入Illuminate\Foundation\Application类的bootstrapWith方法

public function bootstrapWith(array $bootstrappers)
{

    $this->hasBeenBootstrapped = true;

    foreach ($bootstrappers as $bootstrapper) {
        $this['events']->dispatch('bootstrapping: '.$bootstrapper, [$this]);
        // 当循环到\Illuminate\Foundation\Bootstrap\RegisterFacades::class
        // Illuminate\Foundation\Bootstrap\RegisterFacades解析出类的RegisterFacades的实例对象
        // 调用RegisterFacades的bootstrap方法
        $this->make($bootstrapper)->bootstrap($this);

        $this['events']->dispatch('bootstrapped: '.$bootstrapper, [$this]);
    }
}

进入Illuminate\Foundation\Bootstrap\RegisterFacades类，进入bootstrap方法

/**
 * Bootstrap the given application.
 *
 * @param  \Illuminate\Contracts\Foundation\Application  $app
 * @return void
 */
public function bootstrap(Application $app)
{
    Facade::clearResolvedInstances();

    Facade::setFacadeApplication($app);
    // 这里就是上面所说的 核心代码
    // 将config/app.php 里的aliases数组里面的Facades类设置别名
    AliasLoader::getInstance(array_merge(
        $app->make('config')->get('app.aliases', []),
        $app->make(PackageManifest::class)->aliases()
    ))->register();
}