laravel5.5源码笔记（三、门面类facade）

上次说了provider，那么这次来说说facade

首先是启动的源头，从laravel的kernel类中的$bootstrappers 数组，我们可以看到它的一些系统引导方法，其中的registerfacades便是用来注册facade门面类的了。

    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,
    ];

 

 同样是有一个register类，通过这个类进行别名等注册操作

namespace illuminate\foundation\bootstrap;

use illuminate\foundation\aliasloader;
use illuminate\support\facades\facade;
use illuminate\foundation\packagemanifest;
use illuminate\contracts\foundation\application;

class registerfacades
{
    /**
     * bootstrap the given application.
     *
     * @param  \illuminate\contracts\foundation\application  $app
     * @return void
     */
    public function bootstrap(application $app)
    {
        //清除facade所有已绑定实例
        facade::clearresolvedinstances();
        //将app存入对象
        facade::setfacadeapplication($app);
        //将这些别名数组通过构造函数存入对象中
        aliasloader::getinstance(array_merge(
            //通过illuminate\config\repository获取config/app.php中的aliases数组
            $app->make('config')->get('app.aliases', []),
            //还记得最开始的博文中提到的那个包清单吗，这里也从中获取了它的aliases
            $app->make(packagemanifest::class)->aliases()
        //通过spl_autoload_register函数注册另一种自动加载函数
        ))->register();
    }
}

    public static function getinstance(array $aliases = [])
    {
        //注册时的实例是空的，会通过构造方法把刚刚传入的别名数组存入对象
        if (is_null(static::$instance)) {
            return static::$instance = new static($aliases);
        }

        $aliases = array_merge(static::$instance->getaliases(), $aliases);

        static::$instance->setaliases($aliases);

        return static::$instance;
    }

    private function __construct($aliases)
    {
        $this->aliases = $aliases;
    }

    public function register()
    {
        if (! $this->registered) {
            $this->prependtoloaderstack();

            $this->registered = true;
        }
    }

    /**
     * prepend the load method to the auto-loader stack.
     *
     * @return void
     */
    protected function prependtoloaderstack()
    {
        //最后通过自动加载函数将本对象中的load方法放入自动加载队列的前端，在我们通过类名调用方法时，会触发自动加载函数队列，会优先触发这个函数，查找到对应文件的路径然后加载相应文件
        spl_autoload_register([$this, 'load'], true, true);
    }

    public function load($alias)
    {
        //若传入的命名空间不为当前facade数组内才会通过这个方法加载
        if (static::$facadenamespace && strpos($alias, static::$facadenamespace) === 0) {
            $this->loadfacade($alias);

            return true;
        }
        //否则直接返回其别名
        if (isset($this->aliases[$alias])) {
            return class_alias($this->aliases[$alias], $alias);
        }
    }

    /**
     * load a real-time facade for the given alias.
     *
     * @param  string  $alias
     * @return void
     */
    protected function loadfacade($alias)
    {
        require $this->ensurefacadeexists($alias);
    }

    /**
     * ensure that the given alias has an existing real-time facade class.
     *
     * @param  string  $alias
     * @return string
     */
    protected function ensurefacadeexists($alias)
    {
        //从缓存中返回路径
        if (file_exists($path = storage_path('framework/cache/facade-'.sha1($alias).'.php'))) {
            return $path;
        }
        
        file_put_contents($path, $this->formatfacadestub(
            $alias, file_get_contents(__dir__.'/stubs/facade.stub')
        ));

        return $path;
    }

 由于laravel中composer的执行过程过于繁琐，这里就不做深究了。原理是一样的，通过别名找到命名空间的类名，再由composer的类名与文件路径映射关系，自动加载函数找到相应文件加载进来。

 

那么我们来自定义一个门面类试一下

1、新建一个facade类，这里返回的test是上一篇博客中定义的对象

namespace app\facades;

use illuminate\support\facades\facade;

class test extends facade
{
    protected static function getfacadeaccessor()
    {
        return 'app\contracts\test';
    }
}

2、将它添加到config/app.php的aliases别名数组中

'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,
        //刚刚新建的facades
        'test' => \app\facades\test::class,
    ],

3、在路由文件中调用它

route::any('/index', function (){
    test::doing();
});

我们会发现，即使我们没有通过app对象进行make也没有任何命名空间的引入，它就这样被调用了。

如果是在类中调用，那么就要麻烦一些了，需要ues这个别名，注意这一点

namespace app\http\controllers;

use illuminate\http\request;
//use app\contracts\test;
//注意这里只引入了别名，由于命名空间冲突，所以我注释了其他部分
use test;

class indexcontroller extends controller
{
//    public function __construct(test $test)
//    {
//        $this->test = $test;
//    }

    public function index(test $test)
    {
        test::doing();
//        app()->make('app\contracts\test')->doing();
//        echo '<br>';
//
//        //只有通过构造方法进行自动加载依赖的方式才能触发契约的when绑定
//        $this->test->doing();
//
//        echo '<br>';
//        //因为laravel中的上下文绑定只能具体到类，所以这里的$test实例依然为普通绑定
//        $test->doing();

    }
}

 通过这个demo的实践，facade还是比较简单的。