Laravel框架生命周期与原理分析

　　本文实例讲述了Laravel框架生命周期与原理。分享给大家供大家参考，具体如下：

　　引言：

　　如果你对一件工具的使用原理了如指掌，那么你在用这件工具的时候会充满信心！

　　正文：

　　一旦用户（浏览器）发送了一个HTTP请求，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开始的，我们先来看一看这个文件代码。

　　 <?php require __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 clients 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);

　　作者在注释里谈了kernel的作用，kernel的作用，kernel处理来访的请求，并且发送相应返回给用户浏览器。

　　这里又涉及到了一个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\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;

　　请看app变量是Illuminate\Foundation\Application类的对象，所以调用了这个类的构造函数，具体做了什么事，我们看源码。

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

　　构造器做了3件事，前两件事很好理解，创建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，侧面体现程序员是聪明的懒人。

　　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]); // Well 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，分别是HttpKernel，ConsoleKernel，ExceptionHandler。请注意，这里并没有创建对象，只是声明，也只是起了一个“别名”。

　　大家有没有发现，index.php中也有一个$kernel变量，但是只保存了make出来的HttpKernel变量，因此本文不再讨论，ConsoleKernel，ExceptionHandler。。。

　　继续在文件夹下找到App\Http\Kernel.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究竟做了哪些事？

　　 <?php namespace App\Http; use Illuminate\Foundation\Http\Kernel as HttpKernel; class Kernel extends HttpKernel { /** * The applications 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 applications 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 applications 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里定义了中间件数组。

　　该做的做完了，就开始了请求到响应的过程，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，简单归纳整个过程就是：

　　 \bootstrap\app.php，在Application类的构造函数中创建Container，注册了ServiceProvider，定义了别名数组，然后用app变量保存构造函数构造出来的对象。

　　2.使用app这个对象，创建1个单例模式的对象HttpKernel，在创建HttpKernel时调用了构造函数，完成了中间件的声明。

　　3.以上这些工作都是在请求来访之前完成的，接下来开始等待请求，然后就是：接受到请求-->处理请求-->发送响应-->中止app变量

　　更多关于Laravel相关内容感兴趣的读者可查看本站专题：《Laravel框架入门与进阶教程》、《php优秀开发框架总结》、《php面向对象程序设计入门教程》、《php+mysql数据库操作入门教程》及《php常见数据库操作技巧汇总》

　　希望本文所述对大家基于Laravel框架的PHP程序设计有所帮助。