乐正

Actions speak louder than words.

Laravel 源码解读

为WEB艺术家创造的框架

由SitePoint发起的2015年最流行WEB框架的调查中,Laravel已巨大的优势获得了商用使用 数量、个人项目使用数量的第一名。当之无愧是目前最好的WEB框架之一。那么就让我们来 一步一步探究这样优秀的框架究竟是如何实现的吧。

最流行框架投票

目录

入口文件 index.php

一个基于Laravel的应用,当WEB服务器接受到来自外部的请求后,会将这个这个请求解析到 应用根目录的 public/index.php 中。

Laravel源码解读-index.php (laravel_index.php) download
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<?php
/**
 * Laravel - A PHP Framework For Web Artisans
 *
 * @package  Laravel
 * @author   Taylor Otwell <taylorotwell@gmail.com>
 */

/*
|--------------------------------------------------------------------------
| Register The Auto Loader
|--------------------------------------------------------------------------
|
| Composer provides a convenient, automatically generated class loader for
| our application. We just need to utilize it! We'll simply require it
| into the script here so that we don't have to worry about manual
| loading any of our classes later on. It feels nice to relax.
|
*/

require __DIR__.'/../bootstrap/autoload.php';

/*
|--------------------------------------------------------------------------
| Turn On The Lights
|--------------------------------------------------------------------------
|
| We need to illuminate PHP development, so let us turn on the lights.
| This bootstraps the framework and gets it ready for use, then it
| will load up this application so that we can run it and send
| the responses back to the browser and delight our users.
|
*/

$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);

第二十一行代码

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require __DIR__.'/../bootstrap/autoload.php';

为Laravel应用引入了由Composer提供的类加载器,这样Laravel应用便无需再手动加载任 何的类。其加载原理不是此次探究的目标,所以仅仅这样使用就好了。接下的代码,便是重 点。

Illuminate\Foundation\Application 类

该类的继承结构如下:

类继承结构

第三十五行代码

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$app = require_once __DIR__.'/../bootstrap/app.php';

它将我的视线引入到了另外一个文件中,去看看到底发生了什么吧。

Laravel源码解读-app.php (laravel_app.php) download
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<?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;

看第十四行,原来$app是一个 Illuminate\Foundation\Application 对象,那么在创 建这个对象的时候又发生了什么呢?

从它的构造方法看起:

Illuminate\Foundation\Application 构造方法
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/**
 * Create a new Illuminate application instance.
 *
 * @param  string|null  $basePath
 * @return void
 */
public function __construct($basePath = null)
{
    $this->registerBaseBindings();

    $this->registerBaseServiceProviders();

    $this->registerCoreContainerAliases();

    if ($basePath) {
        $this->setBasePath($basePath);
    }
}

顺着函数调用,往下看。在这个构造函数中,首先调用了registerBaseBindings方法。

Illuminate\Foundation\Application#registerBaseBindings
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/**
  * Register the basic bindings into the container.
  *
  * @return void
  */
protected function registerBaseBindings()
{
    static::setInstance($this);

    $this->instance('app', $this);

    $this->instance('Illuminate\Container\Container', $this);
}

这段代码,是将实例对象注入到容器中。那么,这个容器是什么呢?答案还是要从这段调用 中去寻找。

static::setInstance($this) 所做的就是将 $this 赋值给自身的 instance 静态变 量。重点看 $this->instance('app', $this)

instance 函数的作用是绑定一个已有对象到容器中,这个对象在容器中共享并且可以通 过键获取。

Illuminate\Container\Container#instance
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/**
  * Register an existing instance as shared in the container.
  *
  * @param  string  $abstract
  * @param  mixed   $instance
  * @return void
  */
public function instance($abstract, $instance)
{
    if (is_array($abstract)) {
        // $abstract 是这样的一个数组 ['actual key' => 'alias']
        list($abstract, $alias) = $this->extractAlias($abstract);

        // 实际上的行为是 $this->aliases[$alias] = $abstract;
        $this->alias($abstract, $alias);
    }

    unset($this->aliases[$abstract]);

    // 检查是否有这个键是否已经注册到容器中
    // $bound 是一个boolean值
    $bound = $this->bound($abstract);

    $this->instances[$abstract] = $instance;

    if ($bound) {
        $this->rebound($abstract);
    }
}

视线重新回到Application类中,接下来调用了这个方法 $this->registerBaseServiceProviders()

Illuminate\Foundation\Application#registerBaseServiceProviders
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/**
  * Register all of the base service providers.
  *
  * @return void
  */
protected function registerBaseServiceProviders()
{
    $this->register(new EventServiceProvider($this));

    $this->register(new RoutingServiceProvider($this));
}

/**
  * Register a service provider with the application.
  *
  * @param  \Illuminate\Support\ServiceProvider|string  $provider
  * @param  array  $options
  * @param  bool   $force
  * @return \Illuminate\Support\ServiceProvider
  */
public function register($provider, $options = [], $force = false)
{
    if ($registered = $this->getProvider($provider) && !$force) {
        return $registered;
    }

    // If the given "provider" is a string, we will resolve it, passing in the
    // application instance automatically for the developer. This is simply
    // a more convenient way of specifying your service provider classes.
    if (is_string($provider)) {
        $provider = $this->resolveProviderClass($provider);
    }

    $provider->register();

    // Once we have registered the service we will iterate through the options
    // and set each of them on the application so they will be available on
    // the actual loading of the service objects and for developer usage.
    foreach ($options as $key => $value) {
        $this[$key] = $value;
    }

    $this->markAsRegistered($provider);

    // If the application has already booted, we will call this boot method on
    // the provider class so it has an opportunity to do its boot logic and
    // will be ready for any usage by the developer's application logics.
    if ($this->booted) {
        $this->bootProvider($provider);
    }

    return $provider;
}

其中,EventServiceProvider和RoutingServiceProvider分别是

  • Illuminate\Events\EventServiceProvider
  • Illuminate\Routing\RoutingServiceProvider

这些ServiceProvider是 Illuminate\Support\ServiceProvider 的子类,它接受一个 Application 对象作为构造函数参数,存储在实例变量 $app 中。

注入所有基础 Service Provider

register 方法中,每个ServiceProvider被调用了自身的 register 方法。首先看 看 EventServiceProvider 中的吧。

Illuminate\Events\EventServiceProvider#register
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public function register()
{
    $this->app->singleton('events', function ($app) {
        return (new Dispatcher($app))->setQueueResolver(function () use ($app) {
            return $app->make('Illuminate\Contracts\Queue\Factory');
        });
    });
}

上面方法体将一个 Illuminate\Events\Dispatcher 对象以键 events 绑定到了容器 中,它负责实现事件的调度。

再看看 Illuminate\Routing\RoutingServiceProvider:

Illuminate\Routing\RoutingServiceProvider#register
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public function register()
{
    $this->registerRouter();

    $this->registerUrlGenerator();

    $this->registerRedirector();

    $this->registerPsrRequest();

    $this->registerPsrResponse();

    $this->registerResponseFactory();
}

首页是在Laravel中接触的最多的 route 被注册,它是 Illuminate\Routing\Router 对象。

技术

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