看 Laravel 源代碼瞭解 ServiceProvider 的加載

使用 Laravel 開始，咱們老是繞不開 ServiceProvider 這個概念。在 Laravel 框架裏處處充斥着 ServiceProvider —— AppServiceProvider、AuthServiceProvider、BroadcastServiceProvider、EventServiceProvider 和 RouteServiceProvider 等等。

還有咱們在安裝一些第三方插件時，都時不時有這麼句話，將****ServiceProvider 加入到 config/app.php 的 providers 數組中。

難道我們就不想知道 Laravel 是如何加載這些 ServiceProviders 的嗎？

因此今天從源代碼的運行來看看是怎麼實現加載的？

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看 Application 類

咱們都知道 Laravel 的入口文件在 public/index.php

<?php
...
require __DIR__.'/../vendor/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);

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這裏先看載入 require_once __DIR__.'/../bootstrap/app.php'，建立 app 對象。

<?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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直接返回的是 new Illuminate\Foundation\Application( realpath(__DIR__.'/../') Application 對象。

這個對象就是 Laravel 的「容器」。咱們開始看看 Application 是怎麼發現 ServiceProvider 的？

/** * Create a new Illuminate application instance. * * @param string|null $basePath * @return void */
public function __construct($basePath = null) {
    if ($basePath) {
        $this->setBasePath($basePath);
    }

    $this->registerBaseBindings();

    $this->registerBaseServiceProviders();

    $this->registerCoreContainerAliases();
}
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主要是完成這四個方法。第一個和最後一個方法暫且不表；咱們主要看：

$this->registerBaseBindings(); $this->registerBaseServiceProviders();

registerBaseBindings()

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

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

    $this->instance(Container::class, $this);

    $this->instance(PackageManifest::class, new PackageManifest(
        new Filesystem, $this->basePath(), $this->getCachedPackagesPath()
    ));
}
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前兩個主要是綁定 Application 對象和 Container 對象。重點分析 PackageManifest 對象以前，咱們看看 $this->getCachedPackagesPath()這個函數：

/** * Get the path to the cached packages.php file. * * @return string */
public function getCachedPackagesPath() {
    return $this->bootstrapPath().'/cache/packages.php';
}
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這個就是咱們 bootstrap/cache/packages.php文件，這個文件的內容咱們看看：

<?php return array (
  'fideloper/proxy' => 
  array (
    'providers' => 
    array (
      0 => 'Fideloper\\Proxy\\TrustedProxyServiceProvider',
    ),
  ),
  'encore/laravel-admin' => 
  array (
    'providers' => 
    array (
      0 => 'Encore\\Admin\\AdminServiceProvider',
    ),
    'aliases' => 
    array (
      'Admin' => 'Encore\\Admin\\Facades\\Admin',
    ),
  ),
  'laravel/tinker' => 
  array (
    'providers' => 
    array (
      0 => 'Laravel\\Tinker\\TinkerServiceProvider',
    ),
  ),
  'rebing/graphql-laravel' => 
  array (
    'providers' => 
    array (
      0 => 'Rebing\\GraphQL\\GraphQLServiceProvider',
    ),
    'aliases' => 
    array (
      'GraphQL' => 'Rebing\\GraphQL\\Support\\Facades\\GraphQL',
    ),
  ),
  'tymon/jwt-auth' => 
  array (
    'aliases' => 
    array (
      'JWTAuth' => 'Tymon\\JWTAuth\\Facades\\JWTAuth',
      'JWTFactory' => 'Tymon\\JWTAuth\\Facades\\JWTFactory',
    ),
    'providers' => 
    array (
      0 => 'Tymon\\JWTAuth\\Providers\\LaravelServiceProvider',
    ),
  ),
  'noh4ck/graphiql' => 
  array (
    'providers' => 
    array (
      0 => 'Graphiql\\GraphiqlServiceProvider',
    ),
  ),
  'rollbar/rollbar-laravel' => 
  array (
    'providers' => 
    array (
      0 => 'Rollbar\\Laravel\\RollbarServiceProvider',
    ),
    'aliases' => 
    array (
      'Rollbar' => 'Rollbar\\Laravel\\Facades\\Rollbar',
    ),
  ),
  'fanly/log2dingding' => 
  array (
    'providers' => 
    array (
      0 => 'Fanly\\Log2dingding\\FanlyLog2dingdingServiceProvider',
    ),
  ),
);
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經過分析，能夠看出這個文件主要是放着咱們本身引入第三方的 ServiceProviders 和 aliases，咱們對照項目根路徑的 composer.json 你就能夠證明了：

"require": {
    "php": ">=7.0.0",
    "encore/laravel-admin": "1.5.*",
    "fanly/log2dingding": "^0.0.2",
    "fideloper/proxy": "~3.3",
    "guzzlehttp/guzzle": "^6.3",
    "laravel/framework": "5.5.*",
    "laravel/tinker": "~1.0",
    "noh4ck/graphiql": "@dev",
    "overtrue/phplint": "^1.1",
    "rebing/graphql-laravel": "^1.10",
    "rollbar/rollbar-laravel": "^2.3",
    "tymon/jwt-auth": "^1.0@dev"
},
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至於這個 bootstrap/cache/packages.php 文件內容怎麼產生的，咱們後面會說到。

咱們回來分析 new PackageManifest()，類中的幾個函數的做用，顯而易見：

/** * 這個函數是將 package.php 文件的插件數組的 `providers`整合成一個 Collection 輸出 */
public function providers() {}
    
/** * 插件中的 `aliases` 整合成 Collection 輸出。 * * @return array */
public function aliases() {}

/** * 這個是關鍵，從 verdor/composer/installed.json 文件中獲取全部經過 composer 安裝的插件數組，而後再經過用 `name` 綁定對應的 `ServiceProvider`，構成數組，而後再排除每一個插件的 `dont-discover` 和項目 composer.json 填入的 `dont-discover`。 * 這也是 Laravel 包自動發現的核心所在。 * */
public function build() {
    $packages = [];

    if ($this->files->exists($path = $this->vendorPath.'/composer/installed.json')) {
        $packages = json_decode($this->files->get($path), true);
    }

    $ignoreAll = in_array('*', $ignore = $this->packagesToIgnore());

    $this->write(collect($packages)->mapWithKeys(function ($package) {
        return [$this->format($package['name']) => $package['extra']['laravel'] ?? []];
    })->each(function ($configuration) use (&$ignore) {
        $ignore = array_merge($ignore, $configuration['dont-discover'] ?? []);
    })->reject(function ($configuration, $package) use ($ignore, $ignoreAll) {
        return $ignoreAll || in_array($package, $ignore);
    })->filter()->all());
}

/** * 最後就把上面的知足的 ServiceProvider 寫入到文件中，就是上文咱們說的 `bootstrap/cache/packages.php` */
protected function write(array $manifest) {}
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到目前爲止，咱們找到了須要加載的第三方的 ServiceProvider 了。

registerBaseServiceProviders()

接下來咱們看看這個 registerBaseServiceProviders() 方法了。

/** * 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));
}
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這裏主要註冊三個 ServiceProvider，具體功能後面詳聊。

Kernel

咱們簡單過了一遍 new Application，咱們回到 index.php 繼續往下看：

$kernel = $app->make(Illuminate\Contracts\Http\Kernel::class);

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

$response->send();
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這個 $kernel 就是 Laravel 的「核」，而 $kernel->handle() 方法就是 Laravel 的「核中之核」了 —— 即，根據輸入的 Request，輸出 response。完成請求到響應的過程。

咱們進入 $kernel->handle() 方法。

/** * Handle an incoming HTTP request. * * @param \Illuminate\Http\Request $request * @return \Illuminate\Http\Response */
public function handle($request) {
    try {
        $request->enableHttpMethodParameterOverride();

        $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;
}
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排除其它「干擾」東西，眼睛關注到這行代碼：

$response = $this->sendRequestThroughRouter($request);
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這也暴露了，網絡請求的三要素：request、router 和 response。

/** * Send the given request through the middleware / router. * * @param \Illuminate\Http\Request $request * @return \Illuminate\Http\Response */
protected function sendRequestThroughRouter($request) {
    $this->app->instance('request', $request);

    Facade::clearResolvedInstance('request');

    $this->bootstrap();

    return (new Pipeline($this->app))
                ->send($request)
                ->through($this->app->shouldSkipMiddleware() ? [] : $this->middleware)
                ->then($this->dispatchToRouter());
}
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但今天咱們說的不是考慮執行的問題，咱們須要知道何時加載咱們的 ServiceProviders 因此在 return 執行以前的代碼 ($this->bootstrap();) 就是初始化 ServiceProviders等信息的過程

/** * Bootstrap the application for HTTP requests. * * @return void */
public function bootstrap() {
    if (! $this->app->hasBeenBootstrapped()) {
        $this->app->bootstrapWith($this->bootstrappers());
    }
}
    
// Application 類：

/** * Run the given array of bootstrap classes. * * @param array $bootstrappers * @return void */
public function bootstrapWith(array $bootstrappers) {
    $this->hasBeenBootstrapped = true;

    foreach ($bootstrappers as $bootstrapper) {
        $this['events']->fire('bootstrapping: '.$bootstrapper, [$this]);

        $this->make($bootstrapper)->bootstrap($this);

        $this['events']->fire('bootstrapped: '.$bootstrapper, [$this]);
    }
}
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到此咱們知道，實際上遍歷執行 $bootstrappers->bootstrap($this)

此時咱們看看 $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,
    ];
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這六個類的做用主要是：加載環境變量、config、異常處理、註冊 facades、和最後咱們關注的 ServiceProvider 的 register和 boot。

咱們分別來看看。

RegisterProviders

class RegisterProviders {
    /** * Bootstrap the given application. * * @param \Illuminate\Contracts\Foundation\Application $app * @return void */
    public function bootstrap(Application $app) {
        $app->registerConfiguredProviders();
    }
}
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其實是調用 Application 的 registerConfiguredProviders()：

/** * Register all of the configured providers. * * @return void */
public function registerConfiguredProviders() {
    $providers = Collection::make($this->config['app.providers'])
                    ->partition(function ($provider) {
                        return Str::startsWith($provider, 'Illuminate\\');
                    });

    $providers->splice(1, 0, [$this->make(PackageManifest::class)->providers()]);

    (new ProviderRepository($this, new Filesystem, $this->getCachedServicesPath()))
                ->load($providers->collapse()->toArray());
}
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這個就厲害了。加載全部已配置的 ServiceProvider，主要包含了在配置文件 config/app.php 裏的 providers，上文講述的第三方全部知足的 ServiceProviders，以及在 boostrap/cached/service.php 中的全部 Providers。

最後執行 ProviderRepository::load 方法，進行遍歷 register：

/** * Register the application service providers. * * @param array $providers * @return void */
public function load(array $providers) {
    $manifest = $this->loadManifest();

    // First we will load the service manifest, which contains information on all
    // service providers registered with the application and which services it
    // provides. This is used to know which services are "deferred" loaders.
    if ($this->shouldRecompile($manifest, $providers)) {
        $manifest = $this->compileManifest($providers);
    }

    // Next, we will register events to load the providers for each of the events
    // that it has requested. This allows the service provider to defer itself
    // while still getting automatically loaded when a certain event occurs.
    foreach ($manifest['when'] as $provider => $events) {
        $this->registerLoadEvents($provider, $events);
    }

    // We will go ahead and register all of the eagerly loaded providers with the
    // application so their services can be registered with the application as
    // a provided service. Then we will set the deferred service list on it.
    foreach ($manifest['eager'] as $provider) {
        $this->app->register($provider);
    }

    $this->app->addDeferredServices($manifest['deferred']);
}


/** * Register the load events for the given provider. * * @param string $provider * @param array $events * @return void */
protected function registerLoadEvents($provider, array $events) {
    if (count($events) < 1) {
        return;
    }

    $this->app->make('events')->listen($events, function () use ($provider) {
        $this->app->register($provider);
    });
}
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register 以後，咱們能夠看看 boot 方法了。

BootProviders

class BootProviders {
    /** * Bootstrap the given application. * * @param \Illuminate\Contracts\Foundation\Application $app * @return void */
    public function bootstrap(Application $app) {
        $app->boot();
    }
}
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咱們按圖索驥：

/** * Boot the application's service providers. * * @return void */
public function boot() {
    if ($this->booted) {
        return;
    }

    // Once the application has booted we will also fire some "booted" callbacks
    // for any listeners that need to do work after this initial booting gets
    // finished. This is useful when ordering the boot-up processes we run.
    $this->fireAppCallbacks($this->bootingCallbacks);

    array_walk($this->serviceProviders, function ($p) {
        $this->bootProvider($p);
    });

    $this->booted = true;

    $this->fireAppCallbacks($this->bootedCallbacks);
}

...

/** * Boot the given service provider. * * @param \Illuminate\Support\ServiceProvider $provider * @return mixed */
protected function bootProvider(ServiceProvider $provider) {
    if (method_exists($provider, 'boot')) {
        return $this->call([$provider, 'boot']);
    }
}
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也就是說遍歷執行全部 ServiceProviders 的 boot() (前提是該 ServiceProvider 有定義該方法)。

總結

經過分析 index.php 執行過程，發現 Application 主要是發現各類 ServiceProviders，而 $kernel 更多的是在處理 Request請求以前，把全部的 ServiceProvider進行註冊 (register)，而後再 boot。把全部的 ServiceProviders裝載進系統內存中，供處理各式各樣的 Request 使用。

而每個 ServiceProvider 各司其職，負責各自不一樣的職能，來知足 Laravel 系統的各類須要。

下文咱們將重點說說這些 ServiceProvider 的含義和做用。敬請期待！

未完待續