【Laravel-海贼王系列】第十二章，Facade 模式解析

我们经常这样使用一些类

namespace App\Http\Controllers;

use Illuminate\Support\Facades\Log;

class IndexController extends Controller
{
    public function index()
    {
        Log::info('hahaha~');
    }
}
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注册别名

先看对应的 Log 类在框架中注册的部分，在 app.php 文件中的别名数组

'aliases' => [
        'App' => Illuminate\Support\Facades\App::class,
        'Artisan' => Illuminate\Support\Facades\Artisan::class,
        'Auth' => Illuminate\Support\Facades\Auth::class,
        'Blade' => Illuminate\Support\Facades\Blade::class,
        'Broadcast' => Illuminate\Support\Facades\Broadcast::class,
        'Bus' => Illuminate\Support\Facades\Bus::class,
        'Cache' => Illuminate\Support\Facades\Cache::class,
        'Config' => Illuminate\Support\Facades\Config::class,
        'Cookie' => Illuminate\Support\Facades\Cookie::class,
        'Crypt' => Illuminate\Support\Facades\Crypt::class,
        'DB' => Illuminate\Support\Facades\DB::class,
        'Eloquent' => Illuminate\Database\Eloquent\Model::class,
        'Event' => Illuminate\Support\Facades\Event::class,
        'File' => Illuminate\Support\Facades\File::class,
        'Gate' => Illuminate\Support\Facades\Gate::class,
        'Hash' => Illuminate\Support\Facades\Hash::class,
        'Lang' => Illuminate\Support\Facades\Lang::class,
        'Log' => Illuminate\Support\Facades\Log::class,
        'Mail' => Illuminate\Support\Facades\Mail::class,
        'Notification' => Illuminate\Support\Facades\Notification::class,
        'Password' => Illuminate\Support\Facades\Password::class,
        'Queue' => Illuminate\Support\Facades\Queue::class,
        'Redirect' => Illuminate\Support\Facades\Redirect::class,
        'Redis' => Illuminate\Support\Facades\Redis::class,
        'Request' => Illuminate\Support\Facades\Request::class,
        'Response' => Illuminate\Support\Facades\Response::class,
        'Route' => Illuminate\Support\Facades\Route::class,
        'Schema' => Illuminate\Support\Facades\Schema::class,
        'Session' => Illuminate\Support\Facades\Session::class,
        'Storage' => Illuminate\Support\Facades\Storage::class,
        'URL' => Illuminate\Support\Facades\URL::class,
        'Validator' => Illuminate\Support\Facades\Validator::class,
        'View' => Illuminate\Support\Facades\View::class,
    ],
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所以调用的时候实际容器会去解析

lluminate\Support\Facades\Log::class 这个类

我们来看这个类

<?php

namespace Illuminate\Support\Facades;

/**
 * @method static void emergency(string $message, array $context = [])
 * @method static void alert(string $message, array $context = [])
 * @method static void critical(string $message, array $context = [])
 * @method static void error(string $message, array $context = [])
 * @method static void warning(string $message, array $context = [])
 * @method static void notice(string $message, array $context = [])
 * @method static void info(string $message, array $context = [])
 * @method static void debug(string $message, array $context = [])
 * @method static void log($level, string $message, array $context = [])
 * @method static mixed channel(string $channel = null)
 * @method static \Psr\Log\LoggerInterface stack(array $channels, string $channel = null)
 *
 * @see \Illuminate\Log\Logger
 */
class Log extends Facade
{
    protected static function getFacadeAccessor()
    {
        return 'log';
    }
}

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调用分析

最开始我们的调用方法是 Log::info 这里要追踪到父类 Facade 里面

方便阅读精简一些方法

<?php

namespace Illuminate\Support\Facades;

use Closure;
use Mockery;
use RuntimeException;
use Mockery\MockInterface;

abstract class Facade
{
    protected static $app;

    protected static $resolvedInstance;
    
    ...
    
    public static function __callStatic($method, $args)
    {
        $instance = static::getFacadeRoot();

        if (! $instance) {
            throw new RuntimeException('A facade root has not been set.');
        }

        return $instance->$method(...$args);
    }
}

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这里的调用逻辑是通过 __callStatic 这个魔术方法来实现的

public static function __callStatic($method, $args)
    {
        $instance = static::getFacadeRoot();

        if (! $instance) {
            throw new RuntimeException('A facade root has not been set.');
        }

        return $instance->$method(...$args);
    }
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这里也就解释了为什么我们能以静态调用的方式调用对应的方法。

开始分析

$instance = static::getFacadeRoot();
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看样子是要解析一个实例出来,这里要注意的是

static 调用会指向调用的类，其次才是继承的类。

public static function getFacadeRoot()
    {
        return static::resolveFacadeInstance(static::getFacadeAccessor());
    }
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所以这里的 static::getFacadeAccessor() 实际指向 Log 类

protected static function getFacadeAccessor()
    {
        return 'log';
    }
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原来是获取一个别名，那么推测后面就是通过别名从容器拿对象了

继续看看如何拿对象

protected static function resolveFacadeInstance($name)
    {
        if (is_object($name)) {
            return $name;
        }

        if (isset(static::$resolvedInstance[$name])) {
            return static::$resolvedInstance[$name];
        }

        return static::$resolvedInstance[$name] = static::$app[$name];
    }
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看到这里就知道最主要是 static::$app[$name] 来获取对象

拓展- $app 来自哪里?

但是疑问来了， $app 如果是 Application 对象的话又是在什么地方赋值？

回到内核 Kernel 来看看解答,如何启动请回顾 【Laravel-海贼王系列】第四章，Kernel 类解析 的 handle 方法。

protected $bootstrappers = [
        ...
        \Illuminate\Foundation\Bootstrap\RegisterFacades::class,
        ...
    ];
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直接上代码

<?php

namespace Illuminate\Foundation\Bootstrap;

use Illuminate\Foundation\AliasLoader;
use Illuminate\Support\Facades\Facade;
use Illuminate\Foundation\PackageManifest;
use Illuminate\Contracts\Foundation\Application;

class RegisterFacades
{
    public function bootstrap(Application $app)
    {
        Facade::clearResolvedInstances();

        Facade::setFacadeApplication($app);

        AliasLoader::getInstance(array_merge(
            $app->make('config')->get('app.aliases', []),
            $app->make(PackageManifest::class)->aliases()
        ))->register();
    }
}
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真香~, Facade::setFacadeApplication($app); 在这儿传入的 Application 。

这里又涉及到了一些问题，那我怎么知道 $app['log'] 里面的对象是谁呢？

拓展-容器的绑定和解析！

哈哈这里去看 【Laravel-海贼王系列】第三章，Container 类解析 ，里面的 bind() 方法就是在容器中绑定抽象和实现的功能，这里也是容器的知识。 这里的 log 是 Application 在启动的时候提前以及帮我们搞定了~

位于 Application 的 __construct() 中

public function __construct($basePath = null)
    {
        ...
        $this->registerBaseServiceProviders();
        ...
    }
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protected function registerBaseServiceProviders()
    {
        ...
        $this->register(new LogServiceProvider($this));
        ...
    }
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<?php

namespace Illuminate\Log;

use Illuminate\Support\ServiceProvider;

class LogServiceProvider extends ServiceProvider
{
    public function register()
    {
        $this->app->singleton('log', function () {
            return new LogManager($this->app);
        });
    }
}
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最后就看到了真正的对象 return new LogManager($this->app);