Laravel框架生命周期与道理剖析

本文实例讲述了Laravel框架生命周期与道理。分享给大家供大家参考，详细如下：

引言：

如果你对一件工具的使用道理了如指掌，那么你在用这件工具的时候会充满信念！

正文：

一旦会员（阅读器）发送了一个HTTP恳求，我们的apache或者nginx一般都转到index.php，因此，之后的一系列步骤都是从index.php开端的，我们先来看一看这个文件代码。

make(Illuminate\Contracts\Http\Kernel::class);
$response = $kernel->handle(
  $request = Illuminate\Http\Request::capture()
);
$response->send();
$kernel->terminate($request, $response);

作者在注释里谈了kernel的作用，kernel的作用，kernel处置来访的恳求，并且发送响应返回给会员阅读器。

这里又触及到了一个app对象，所以附上app对象，所以附上app对象的源码，这份源码是bootstrapapp.php

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;

请看app变量是IlluminateFoundationApplication类的对象，所以调用了这个类的结构函数，详细做了什么事，我们看源码。

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

结构器做了3件事，前两件事很好理解，创立Container，注册了ServiceProvider，看代码

/**
 * 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，是做了个很大的数组，定义了大量的别名，侧面表现程序员是聪明的懒人。

/**
 * 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);
    }
  }
}

这里出现了一个instance函数，其实这并不是Application类的函数，而是Application类的父类Container类的函数

/**
 * 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的子类，所以$app不仅是Application类的对象，还是Container的对象，所以，新出现的singleton函数我们就可以到Container类的源代码文件里查。bind函数和singleton的区别见这篇博文。

singleton这个函数，前一个参数是实际类名，后一个参数是类的“别名”。

$app对象声明了3个单例模型对象，离别是HttpKernel，ConsoleKernel，ExceptionHandler。请留意，这里并没有创立对象，只是声明，也只是起了一个“别名”。

大家有没有发明，index.php中也有一个$kernel变量，但是只留存了make出来的HttpKernel变量，因此本文不再计议，ConsoleKernel，ExceptionHandler。。。

继续在文件夹下找到AppHttpKernel.php，既然我们把实际的HttpKernel做的事情都写在这个php文件里，就从这份代码里看看毕竟做了哪些事？

 [
      \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里定义了中心件数组。

该做的做完了，就开端了恳求到响应的历程，见index.php

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

最后在中止，释放所有资源。

/**
* 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();
}

总结一下，简便归纳整个历程就是：

1.index.php加载bootstrapapp.php，在Application类的结构函数中创立Container，注册了ServiceProvider，定义了别名数组，然后用app变量留存结构函数结构出来的对象。

2.使用app这个对象，创立1个单例模式的对象HttpKernel，在创立HttpKernel时调用了结构函数，完成了中心件的声明。

3.以上这些工作都是在恳求来访此前完成的，接下来开端等候恳求，然后就是：接受到恳求-->处置恳求-->发送响应-->中止app变量