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如果你對一件工具的使用原理了如指掌，那么你在用這件工具的時候會充滿信心！

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一旦用戶（瀏覽器）發送了一個HTTP請求，我們的apache或者nginx一般都轉到index.php，因此，之后的一系列步驟都是從index.php開始的，我們先來看一看這個文件代碼。

<?phprequire __DIR__.'/../bootstrap/autoload.php';$app = require_once __DIR__.'/../bootstrap/app.php';/* |-------------------------------------------------------------------------- | Run The Application |-------------------------------------------------------------------------- | | Once we have the application, we can handle the incoming request | through the kernel, and send the associated response back to | the client's browser allowing them to enjoy the creative | and wonderful application we have prepared for them. | */$kernel = $app->make(Illuminate\Contracts\Http\Kernel::class);$response = $kernel->handle($request = Illuminate\Http\Request::capture() );$response->send();$kernel->terminate($request, $response);

作者在注釋里談了$kernel的作用，$kernel處理來訪的請求，并且發送相應返回給用戶瀏覽器。

這里又涉及到了一個$app對象，所以附上$app對象的源碼，這份源碼是\bootstrap\app.php

<?php /* |-------------------------------------------------------------------------- | Create The Application |-------------------------------------------------------------------------- | | The first thing we will do is create a new Laravel application instance | which serves as the "glue" for all the components of Laravel, and is | the IoC container for the system binding all of the various parts. | */ $app = new Illuminate\Foundation\Application(realpath(__DIR__.'/../') ); /* |-------------------------------------------------------------------------- | Bind Important Interfaces |-------------------------------------------------------------------------- | | Next, we need to bind some important interfaces into the container so | we will be able to resolve them when needed. The kernels serve the | incoming requests to this application from both the web and CLI. | */ $app->singleton(Illuminate\Contracts\Http\Kernel::class,App\Http\Kernel::class ); $app->singleton(Illuminate\Contracts\Console\Kernel::class,App\Console\Kernel::class ); $app->singleton(Illuminate\Contracts\Debug\ExceptionHandler::class,App\Exceptions\Handler::class ); /* |-------------------------------------------------------------------------- | Return The Application |-------------------------------------------------------------------------- | | This script returns the application instance. The instance is given to | the calling script so we can separate the building of the instances | from the actual running of the application and sending responses. | */ return $app;

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請看app變量是Illuminate\Foundation\Application類的對象，所以調用了這個類的構造函數，具體做了什么事，我們看源碼。

public function __construct($basePath = null){if ($basePath) {$this->setBasePath($basePath);}$this->registerBaseBindings();$this->registerBaseServiceProviders();$this->registerCoreContainerAliases();}

構造器做了3件事，前兩件事很好理解，創建Container，注冊了ServiceProvider，看代碼

/*** Register the basic bindings into the container.** @return void*/protected function registerBaseBindings(){static::setInstance($this);$this->instance('app', $this);$this->instance(Container::class, $this);}/*** Register all of the base service providers.** @return void*/protected function registerBaseServiceProviders(){$this->register(new EventServiceProvider($this));$this->register(new LogServiceProvider($this));$this->register(new RoutingServiceProvider($this));}

最后一件事，是做了個很大的數組，定義了大量的別名，側面體現程序員是聰明的懶人。

/*** Register the core class aliases in the container.** @return void*/public function registerCoreContainerAliases(){$aliases = ['app' => [\Illuminate\Foundation\Application::class, \Illuminate\Contracts\Container\Container::class, \Illuminate\Contracts\Foundation\Application::class],'auth' => [\Illuminate\Auth\AuthManager::class, \Illuminate\Contracts\Auth\Factory::class],'auth.driver' => [\Illuminate\Contracts\Auth\Guard::class],'blade.compiler' => [\Illuminate\View\Compilers\BladeCompiler::class],'cache' => [\Illuminate\Cache\CacheManager::class, \Illuminate\Contracts\Cache\Factory::class],'cache.store' => [\Illuminate\Cache\Repository::class, \Illuminate\Contracts\Cache\Repository::class],'config' => [\Illuminate\Config\Repository::class, \Illuminate\Contracts\Config\Repository::class],'cookie' => [\Illuminate\Cookie\CookieJar::class, \Illuminate\Contracts\Cookie\Factory::class, \Illuminate\Contracts\Cookie\QueueingFactory::class],'encrypter' => [\Illuminate\Encryption\Encrypter::class, \Illuminate\Contracts\Encryption\Encrypter::class],'db' => [\Illuminate\Database\DatabaseManager::class],'db.connection' => [\Illuminate\Database\Connection::class, \Illuminate\Database\ConnectionInterface::class],'events' => [\Illuminate\Events\Dispatcher::class, \Illuminate\Contracts\Events\Dispatcher::class],'files' => [\Illuminate\Filesystem\Filesystem::class],'filesystem' => [\Illuminate\Filesystem\FilesystemManager::class, \Illuminate\Contracts\Filesystem\Factory::class],'filesystem.disk' => [\Illuminate\Contracts\Filesystem\Filesystem::class],'filesystem.cloud' => [\Illuminate\Contracts\Filesystem\Cloud::class],'hash' => [\Illuminate\Contracts\Hashing\Hasher::class],'translator' => [\Illuminate\Translation\Translator::class, \Illuminate\Contracts\Translation\Translator::class],'log' => [\Illuminate\Log\Writer::class, \Illuminate\Contracts\Logging\Log::class, \Psr\Log\LoggerInterface::class],'mailer' => [\Illuminate\Mail\Mailer::class, \Illuminate\Contracts\Mail\Mailer::class, \Illuminate\Contracts\Mail\MailQueue::class],'auth.password' => [\Illuminate\Auth\Passwords\PasswordBrokerManager::class, \Illuminate\Contracts\Auth\PasswordBrokerFactory::class],'auth.password.broker' => [\Illuminate\Auth\Passwords\PasswordBroker::class, \Illuminate\Contracts\Auth\PasswordBroker::class],'queue' => [\Illuminate\Queue\QueueManager::class, \Illuminate\Contracts\Queue\Factory::class, \Illuminate\Contracts\Queue\Monitor::class],'queue.connection' => [\Illuminate\Contracts\Queue\Queue::class],'queue.failer' => [\Illuminate\Queue\Failed\FailedJobProviderInterface::class],'redirect' => [\Illuminate\Routing\Redirector::class],'redis' => [\Illuminate\Redis\RedisManager::class, \Illuminate\Contracts\Redis\Factory::class],'request' => [\Illuminate\Http\Request::class, \Symfony\Component\HttpFoundation\Request::class],'router' => [\Illuminate\Routing\Router::class, \Illuminate\Contracts\Routing\Registrar::class, \Illuminate\Contracts\Routing\BindingRegistrar::class],'session' => [\Illuminate\Session\SessionManager::class],'session.store' => [\Illuminate\Session\Store::class, \Illuminate\Contracts\Session\Session::class],'url' => [\Illuminate\Routing\UrlGenerator::class, \Illuminate\Contracts\Routing\UrlGenerator::class],'validator' => [\Illuminate\Validation\Factory::class, \Illuminate\Contracts\Validation\Factory::class],'view' => [\Illuminate\View\Factory::class, \Illuminate\Contracts\View\Factory::class],];foreach ($aliases as $key => $aliases) {foreach ($aliases as $alias) {$this->alias($key, $alias);}}}

這里出現了一個instance函數，其實這并不是Application類的函數，而是Application類的父類Container類的函數

/*** Register an existing instance as shared in the container.** @param string $abstract* @param mixed $instance* @return void*/public function instance($abstract, $instance){$this->removeAbstractAlias($abstract);unset($this->aliases[$abstract]);// We'll check to determine if this type has been bound before, and if it has// we will fire the rebound callbacks registered with the container and it// can be updated with consuming classes that have gotten resolved here.$this->instances[$abstract] = $instance;if ($this->bound($abstract)) {$this->rebound($abstract);}}

Application是Container的子類，所以$app不僅是Application類的對象，還是Container的對象，所以，新出現的singleton函數我們就可以到Container類的源代碼文件里查。bind函數和singleton的區別見這篇博文。

singleton這個函數，前一個參數是實際類名，后一個參數是類的“別名”。

$app對象聲明了3個單例模型對象，分別是HttpKernel，ConsoleKernel，ExceptionHandler。請注意，這里并沒有創建對象，只是聲明，也只是起了一個“別名”。

大家有沒有發現，index.php中也有一個$kernel變量，但是只保存了make出來的HttpKernel變量，因此本文不再討論，ConsoleKernel，ExceptionHandler。。。

繼續在文件夾下找到App\Http\Kernel.php，既然我們把實際的HttpKernel做的事情都寫在這個php文件里，就從這份代碼里看看究竟做了哪些事？

<?phpnamespace App\Http;use Illuminate\Foundation\Http\Kernel as HttpKernel;class Kernel extends HttpKernel {/*** The application's global HTTP middleware stack.** These middleware are run during every request to your application.** @var array*/protected $middleware = [\Illuminate\Foundation\Http\Middleware\CheckForMaintenanceMode::class,//\App\Http\Middleware\MyMiddleware::class,];/*** The application's route middleware groups.** @var array*/protected $middlewareGroups = ['web' => [\App\Http\Middleware\EncryptCookies::class,\Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse::class,\Illuminate\Session\Middleware\StartSession::class,\Illuminate\View\Middleware\ShareErrorsFromSession::class,\App\Http\Middleware\VerifyCsrfToken::class,],'api' => ['throttle:60,1',],];/*** The application's route middleware.** These middleware may be assigned to groups or used individually.** @var array*/protected $routeMiddleware = ['auth' => \App\Http\Middleware\Authenticate::class,'auth.basic' => \Illuminate\Auth\Middleware\AuthenticateWithBasicAuth::class,'guest' => \App\Http\Middleware\RedirectIfAuthenticated::class,'throttle' => \Illuminate\Routing\Middleware\ThrottleRequests::class,'mymiddleware'=>\App\Http\Middleware\MyMiddleware::class,]; }

一目了然，HttpKernel里定義了中間件數組。

該做的做完了，就開始了請求到響應的過程，見index.php

$response = $kernel->handle($request = Illuminate\Http\Request::capture() ); $response->send();

最后在中止，釋放所有資源。

/*** Call the terminate method on any terminable middleware.** @param \Illuminate\Http\Request $request* @param \Illuminate\Http\Response $response* @return void*/public function terminate($request, $response){$this->terminateMiddleware($request, $response);$this->app->terminate();}

　　

總結一下，簡單歸納整個過程就是：

1.index.php加載\bootstrap\app.php，在Application類的構造函數中創建Container，注冊了ServiceProvider，定義了別名數組，然后用app變量保存構造函數構造出來的對象。

2.使用app這個對象，創建1個單例模式的對象HttpKernel，在創建HttpKernel時調用了構造函數，完成了中間件的聲明。

3.以上這些工作都是在請求來訪之前完成的，接下來開始等待請求，然后就是：接受到請求-->處理請求-->發送響應-->中止app變量

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轉載于:https://www.cnblogs.com/sweng/p/6391542.html

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