深入剖析 Laravel 服务容器

    /**
     * Create a new Illuminate application instance.
     *
     * @see https://github.com/laravel/framework/blob/5.6/src/Illuminate/Foundation/Application.php#L162:27
     * @param  string|null  $basePath
     * @return void
     */
    public function __construct($basePath = null)
    {
        if ($basePath) {
            $this->setBasePath($basePath);
        }
        $this->registerBaseBindings();
        $this->registerBaseServiceProviders();
        $this->registerCoreContainerAliases();
    }Copy

    /**
     * Register the basic bindings into the container. 注册 App 实例本身到 App 容器
     *
     * @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()
        ));
    }Copy

<?php
$dependency = new ConfigDependency(config('cache.config.setting'));
$cache = new MemcachedCache($dependency);Copy

<?php
App::bind(Cache::class, function () {
    $dependency = new ConfigDependency(config('cache.config.setting'));
    return $cache = new MemcachedCache($dependency);
});Copy

<?php
$cache = App::make(Cache::class);Copy

App::singleton(Cache::class, function () {
    $dependency = new ConfigDependency(config('cache.config.setting'));
    return $cache = new MemcachedCache($dependency);
});Copy

<?php
// 创建一个用户实例
$artisan = new User('柳公子');

// 将实例绑定到服务容器
App::instance('login-user', $artisan);

// 获取用户实例
$artisan = App::make('login-user');Copy

use Illuminate\Support\Facades\Storage;
use App\Http\Controllers\PhotoController;
use App\Http\Controllers\VideoController;
use Illuminate\Contracts\Filesystem\Filesystem;

$this->app->when(PhotoController::class)
          ->needs(Filesystem::class)
          ->give(function () {
              return Storage::disk('local');
          });

$this->app->when(VideoController::class)
          ->needs(Filesystem::class)
          ->give(function () {
              return Storage::disk('s3');
          });Copy

function () {
    return Storage::disk('local');
}Copy

function () {
    return Storage::disk('s3');
}Copy

<?php
namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Models\User;
class UserController
{
    private $user = null;

    public function __construct(User $user)
    {
        $this->user = $user;
    }
}
Copy

    /**
     * Create a new Illuminate application instance.
     *
     * @see https://github.com/laravel/framework/blob/5.6/src/Illuminate/Foundation/Application.php#L162:27
     * @param  string|null  $basePath
     * @return void
     */
    public function __construct($basePath = null)
    {
        if ($basePath) {
            $this->setBasePath($basePath);
        }
        $this->registerBaseBindings();
        $this->registerBaseServiceProviders();
        $this->registerCoreContainerAliases();
    }Copy

    /**
     * Register all of the base service providers. 注册应用基础服务提供者
     *
     * @return void
     */
    protected function registerBaseServiceProviders()
    {
        $this->register(new EventServiceProvider($this));
        $this->register(new LogServiceProvider($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 = $this->resolveProvider($provider);
        }

        // 当服务提供者存在 register 方法时，执行 register 方法，完成绑定处理
        if (method_exists($provider, 'register')) {
            $provider->register();
        }

        $this->markAsRegistered($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 this developer's application logic.
        // 执行服务提供者 boot 方法启动程序
        if ($this->booted) {
            $this->bootProvider($provider);
        }

        return $provider;
    }

    /**
     * Boot the given service provider. 启动给定服务提供者
     *
     * @param  \Illuminate\Support\ServiceProvider  $provider
     * @return mixed
     */
    protected function bootProvider(ServiceProvider $provider)
    {
        if (method_exists($provider, 'boot')) {
            return $this->call([$provider, 'boot']);
        }
    }Copy

<?php

namespace Illuminate\Events;

use Illuminate\Support\ServiceProvider;
use Illuminate\Contracts\Queue\Factory as QueueFactoryContract;

class EventServiceProvider extends ServiceProvider
{
    /**
     * Register the service provider. 注册服务提供者
     *
     * @return void
     */
    public function register()
    {
        $this->app->singleton('events', function ($app) {
            return (new Dispatcher($app))->setQueueResolver(function () use ($app) {
                return $app->make(QueueFactoryContract::class);
            });
        });
    }
}
Copy

Route::get('/', function() {
    return 'Hello World';
});Copy

    /**
     * Register the core class aliases in the container. 在容器中注册核心服务的别名
     *
     * @return void
     */
    public function registerCoreContainerAliases()
    {
        foreach ([
            'app'                  => [\Illuminate\Foundation\Application::class, \Illuminate\Contracts\Container\Container::class, \Illuminate\Contracts\Foundation\Application::class,  \Psr\Container\ContainerInterface::class],
            'auth'                 => [\Illuminate\Auth\AuthManager::class, \Illuminate\Contracts\Auth\Factory::class],
            'auth.driver'          => [\Illuminate\Contracts\Auth\Guard::class],
            'blade.compiler'       => [\Illuminate\View\Compilers\BladeCompiler::class],
            'cache'                => [\Illuminate\Cache\CacheManager::class, \Illuminate\Contracts\Cache\Factory::class],
            'cache.store'          => [\Illuminate\Cache\Repository::class, \Illuminate\Contracts\Cache\Repository::class],
            'config'               => [\Illuminate\Config\Repository::class, \Illuminate\Contracts\Config\Repository::class],
            'cookie'               => [\Illuminate\Cookie\CookieJar::class, \Illuminate\Contracts\Cookie\Factory::class, \Illuminate\Contracts\Cookie\QueueingFactory::class],
            'encrypter'            => [\Illuminate\Encryption\Encrypter::class, \Illuminate\Contracts\Encryption\Encrypter::class],
            'db'                   => [\Illuminate\Database\DatabaseManager::class],
            'db.connection'        => [\Illuminate\Database\Connection::class, \Illuminate\Database\ConnectionInterface::class],
            'events'               => [\Illuminate\Events\Dispatcher::class, \Illuminate\Contracts\Events\Dispatcher::class],
            'files'                => [\Illuminate\Filesystem\Filesystem::class],
            'filesystem'           => [\Illuminate\Filesystem\FilesystemManager::class, \Illuminate\Contracts\Filesystem\Factory::class],
            'filesystem.disk'      => [\Illuminate\Contracts\Filesystem\Filesystem::class],
            'filesystem.cloud'     => [\Illuminate\Contracts\Filesystem\Cloud::class],
            'hash'                 => [\Illuminate\Contracts\Hashing\Hasher::class],
            'translator'           => [\Illuminate\Translation\Translator::class, \Illuminate\Contracts\Translation\Translator::class],
            'log'                  => [\Illuminate\Log\Writer::class, \Illuminate\Contracts\Logging\Log::class, \Psr\Log\LoggerInterface::class],
            'mailer'               => [\Illuminate\Mail\Mailer::class, \Illuminate\Contracts\Mail\Mailer::class, \Illuminate\Contracts\Mail\MailQueue::class],
            'auth.password'        => [\Illuminate\Auth\Passwords\PasswordBrokerManager::class, \Illuminate\Contracts\Auth\PasswordBrokerFactory::class],
            'auth.password.broker' => [\Illuminate\Auth\Passwords\PasswordBroker::class, \Illuminate\Contracts\Auth\PasswordBroker::class],
            'queue'                => [\Illuminate\Queue\QueueManager::class, \Illuminate\Contracts\Queue\Factory::class, \Illuminate\Contracts\Queue\Monitor::class],
            'queue.connection'     => [\Illuminate\Contracts\Queue\Queue::class],
            'queue.failer'         => [\Illuminate\Queue\Failed\FailedJobProviderInterface::class],
            'redirect'             => [\Illuminate\Routing\Redirector::class],
            'redis'                => [\Illuminate\Redis\RedisManager::class, \Illuminate\Contracts\Redis\Factory::class],
            'request'              => [\Illuminate\Http\Request::class, \Symfony\Component\HttpFoundation\Request::class],
            'router'               => [\Illuminate\Routing\Router::class, \Illuminate\Contracts\Routing\Registrar::class, \Illuminate\Contracts\Routing\BindingRegistrar::class],
            'session'              => [\Illuminate\Session\SessionManager::class],
            'session.store'        => [\Illuminate\Session\Store::class, \Illuminate\Contracts\Session\Session::class],
            'url'                  => [\Illuminate\Routing\UrlGenerator::class, \Illuminate\Contracts\Routing\UrlGenerator::class],
            'validator'            => [\Illuminate\Validation\Factory::class, \Illuminate\Contracts\Validation\Factory::class],
            'view'                 => [\Illuminate\View\Factory::class, \Illuminate\Contracts\View\Factory::class],
        ] as $key => $aliases) {
            foreach ($aliases as $alias) {
                $this->alias($key, $alias);
            }
        }
    }Copy

    /**
     * Register a binding with the container.
     *
     * @param  string  $abstract
     * @param  \Closure|string|null  $concrete
     * @param  bool  $shared
     * @return void
     */
    public function bind($abstract, $concrete = null, $shared = false)
    {
        // 如果未提供实现类 $concrete，我们直接将抽象类作为实现 $abstract。
        // 这之后，我们无需明确指定 $abstract 和 $concrete 是否为单例模式，
        // 而是通过 $shared 标识来决定它们是单例还是每次都需要实例化处理。
        $this->dropStaleInstances($abstract);

        if (is_null($concrete)) {
            $concrete = $abstract;
        }

        // 如果绑定时传入的实现类非闭包，即绑定时是直接给定了实现类的类名，
        // 这时要稍微处理下将类名封装成一个闭包，保证解析时处理手法的统一。
        if (! $concrete instanceof Closure) {
            $concrete = $this->getClosure($abstract, $concrete);
        }

        $this->bindings[$abstract] = compact('concrete', 'shared');

        // 最后如果抽象类已经被容器解析过，我们将触发 rebound 监听器。
        // 并且通过触发 rebound 监听器回调，将任何已被解析过的服务更新最新的实现到抽象接口。
        if ($this->resolved($abstract)) {
            $this->rebound($abstract);
        }
    }

    /**
     * Get the Closure to be used when building a type. 当绑定实现为类名时，则封装成闭包并返回。
     *
     * @param  string  $abstract
     * @param  string  $concrete
     * @return \Closure
     */
    protected function getClosure($abstract, $concrete)
    {
        return function ($container, $parameters = []) use ($abstract, $concrete) {
            if ($abstract == $concrete) {
                return $container->build($concrete);
            }

            return $container->make($concrete, $parameters);
        };
    }

    /**
     * Fire the "rebound" callbacks for the given abstract type. 依据给定的抽象服务接口，触发其 "rebound" 回调
     *
     * @param  string  $abstract
     * @return void
     */
    protected function rebound($abstract)
    {
        $instance = $this->make($abstract);

        foreach ($this->getReboundCallbacks($abstract) as $callback) {
            call_user_func($callback, $this, $instance);
        }
    }

    /**
     * Get the rebound callbacks for a given type. 获取给定抽象服务的回调函数。
     *
     * @param  string  $abstract
     * @return array
     */
    protected function getReboundCallbacks($abstract)
    {
        if (isset($this->reboundCallbacks[$abstract])) {
            return $this->reboundCallbacks[$abstract];
        }

        return [];
    }Copy

    /**
     * Resolve the given type from the container. 从容器中解析出给定服务具体实现
     *
     * @param  string  $abstract
     * @param  array  $parameters
     * @return mixed
     */
    public function make($abstract, array $parameters = [])
    {
        return $this->resolve($abstract, $parameters);
    }

    /**
     * Resolve the given type from the container. 从容器中解析出给定服务具体实现
     *
     * @param  string  $abstract
     * @param  array  $parameters
     * @return mixed
     */
    protected function resolve($abstract, $parameters = [])
    {
        $abstract = $this->getAlias($abstract);

        // 如果绑定时基于上下文绑定，此时需要解析出上下文实现类
        $needsContextualBuild = ! empty($parameters) || ! is_null(
            $this->getContextualConcrete($abstract)
        );

        // 如果给定的类型已单例模式绑定，直接从服务容器中返回这个实例而无需重新实例化
        if (isset($this->instances[$abstract]) && ! $needsContextualBuild) {
            return $this->instances[$abstract];
        }

        $this->with[] = $parameters;

        $concrete = $this->getConcrete($abstract);

        // 已准备就绪创建这个绑定的实例。下面将实例化给定实例及内嵌的所有依赖实例。
        // 到这里我们已经做好创建实例的准备工作。只有可以构建的服务才可以执行 build 方法去实例化服务；
        // 否则也就是说我们的服务还存在依赖，然后不断的去解析嵌套的依赖，知道它们可以去构建（isBuildable）。
        if ($this->isBuildable($concrete, $abstract)) {
            $object = $this->build($concrete);
        } else {
            $object = $this->make($concrete);
        }

        // 如果我们的服务存在扩展（extend）绑定，此时就需要去执行扩展。
        // 扩展绑定适用于修改服务的配置或者修饰（decorating）服务实现。
        foreach ($this->getExtenders($abstract) as $extender) {
            $object = $extender($object, $this);
        }

        // 如果我们的服务已单例模式绑定，此时无要将已解析的服务缓存到单例对象池中（instances），
        // 后续便可以直接获取单例服务对象了。
        if ($this->isShared($abstract) && ! $needsContextualBuild) {
            $this->instances[$abstract] = $object;
        }

        $this->fireResolvingCallbacks($abstract, $object);

        $this->resolved[$abstract] = true;

        array_pop($this->with);

        return $object;
    }

    /**
     * Determine if the given concrete is buildable. 判断给定的实现是否立马进行构建
     *
     * @param  mixed   $concrete
     * @param  string  $abstract
     * @return bool
     */
    protected function isBuildable($concrete, $abstract)
    {
        // 仅当实现类和接口相同或者实现为闭包时可构建
        return $concrete === $abstract || $concrete instanceof Closure;
    }

    /**
     * Instantiate a concrete instance of the given type. 构建（实例化）给定类型的实现类(匿名函数)实例
     *
     * @param  string  $concrete
     * @return mixed
     *
     * @throws \Illuminate\Contracts\Container\BindingResolutionException
     */
    public function build($concrete)
    {
        // 如果给定的实现是一个闭包，直接执行并闭包，返回执行结果
        if ($concrete instanceof Closure) {
            return $concrete($this, $this->getLastParameterOverride());
        }

        $reflector = new ReflectionClass($concrete);

        // 如果需要解析的类无法实例化，即试图解析一个抽象类类型如: 接口或抽象类而非实现类，直接抛出异常。
        if (! $reflector->isInstantiable()) {
            return $this->notInstantiable($concrete);
        }

        $this->buildStack[] = $concrete;

        // 通过反射获取实现类构造函数
        $constructor = $reflector->getConstructor();

        // 如果实现类并没有定义构造函数，说明这个实现类没有相关依赖。
        // 我们可以直接实例化这个实现类，而无需自动解析依赖（自动注入）。
        if (is_null($constructor)) {
            array_pop($this->buildStack);

            return new $concrete;
        }

        // 获取到实现类构造函数依赖参数
        $dependencies = $constructor->getParameters();

        // 解析出所有依赖
        $instances = $this->resolveDependencies(
            $dependencies
        );

        array_pop($this->buildStack);

        // 这是我们就可以创建服务实例并返回。
        return $reflector->newInstanceArgs($instances);
    }

    /**
     * Resolve all of the dependencies from the ReflectionParameters. 从 ReflectionParameters 解析出所有构造函数所需依赖
     *
     * @param  array  $dependencies
     * @return array
     */
    protected function resolveDependencies(array $dependencies)
    {
        $results = [];

        foreach ($dependencies as $dependency) {
            // If this dependency has a override for this particular build we will use
            // that instead as the value. Otherwise, we will continue with this run
            // of resolutions and let reflection attempt to determine the result.
            if ($this->hasParameterOverride($dependency)) {
                $results[] = $this->getParameterOverride($dependency);

                continue;
            }

            // 构造函数参数为非类时，即参数为 string、int 等标量类型或闭包时，按照标量和闭包解析；
            // 否则需要解析类。
            $results[] = is_null($dependency->getClass())
                            ? $this->resolvePrimitive($dependency)
                            : $this->resolveClass($dependency);
        }

        return $results;
    }

    /**
     * Resolve a non-class hinted primitive dependency. 依据类型提示解析出标量类型（闭包）数据
     *
     * @param  \ReflectionParameter  $parameter
     * @return mixed
     *
     * @throws \Illuminate\Contracts\Container\BindingResolutionException
     */
    protected function resolvePrimitive(ReflectionParameter $parameter)
    {
        if (! is_null($concrete = $this->getContextualConcrete('$'.$parameter->name))) {
            return $concrete instanceof Closure ? $concrete($this) : $concrete;
        }

        if ($parameter->isDefaultValueAvailable()) {
            return $parameter->getDefaultValue();
        }

        $this->unresolvablePrimitive($parameter);
    }

    /**
     * Resolve a class based dependency from the container. 从服务容器中解析出类依赖（自动注入）
     *
     * @param  \ReflectionParameter  $parameter
     * @return mixed
     *
     * @throws \Illuminate\Contracts\Container\BindingResolutionException
     */
    protected function resolveClass(ReflectionParameter $parameter)
    {
        try {
            return $this->make($parameter->getClass()->name);
        }

        catch (BindingResolutionException $e) {
            if ($parameter->isOptional()) {
                return $parameter->getDefaultValue();
            }

            throw $e;
        }
    }Copy