Symfony 4：DependencyInjection 组件 - 未捕获的 ReflectionException：类不存在

Question

我正在尝试将 Symfony（版本 4.0.0）中的 DependencyInjection Component 实施到我的项目中。为此，我遵循以下简单步骤，以了解autowiring 流程：

• 在composer.json 中：将命名空间App 分配给src 文件夹。
• 在services.yaml 中：将命名空间App 分配给src 文件夹。
• 在命名空间App\Controller 下的src 文件夹中定义MyController 类。
• 在bootstrap.php 中：创建ContainerBuilder 实例($container)。
• 在bootstrap.php中：创建一个YamlFileLoader对象并将配置文件services.yaml加载到其中。
• 在bootstrap.php 中：从$container 中获取MyController 的实例并将其显示在屏幕上。

但我不断收到以下错误：

( ! ) Fatal error: Uncaught ReflectionException: Class does not exist in <path-to-my-project-root>/vendor/symfony/dependency-injection/ContainerBuilder.php on line 1051
( ! ) ReflectionException: Class does not exist in <path-to-my-project-root>/vendor/symfony/dependency-injection/ContainerBuilder.php on line 1051
Call Stack
#   Time    Memory  Function    Location
1   0.0160  354632  {main}( )   .../index.php:0
2   0.0166  357928  require_once( '<path-to-my-project-root>/bootstrap.php' ) .../index.php:7
3   0.0872  1752040 Symfony\Component\DependencyInjection\ContainerBuilder->get( )  .../bootstrap.php:16
4   0.0872  1752040 Symfony\Component\DependencyInjection\ContainerBuilder->doGet( )    .../ContainerBuilder.php:522
5   0.0872  1752816 Symfony\Component\DependencyInjection\ContainerBuilder->createService( )    .../ContainerBuilder.php:555
6   0.0873  1752928 __construct ( ) .../ContainerBuilder.php:1051

错误发生在ContainerBulder::createService方法的这一行(1051)，因为$definition->getClass()返回NULL：

private function createService(Definition $definition, array &$inlineServices, $id = null, $tryProxy = true) {
    // Line 1051:    
    $r = new \ReflectionClass($class = $parameterBag->resolveValue($definition->getClass()));

    //..
}

在Automatic Service Loading in services.yaml章节中，据我了解，通过仅使用services.yaml中的那些设置而不使用任何其他设置，DI容器将知道如何创建MyController的实例。也许我错了？...

您能帮我一下吗？非常感谢。

---

我的项目由以下结构和文件组成：

项目结构

bootstrap.php
composer.json
config/
    services.yaml
src/
    Controller/
        MyController
vendor/
    symfony/
        config/
        dependency-injection/
        filesystem/
        polyfill-mbstring/
        yaml/

composer.json

"require": {
    "php": ">=5.5.0",
    "symfony/dependency-injection": "^4.0",
    "symfony/config": "^4.0",
    "symfony/yaml": "^4.0",
},
"autoload": {
    "psr-4": {
        "App\\": "src/"
    }
}

bootstrap.php

<?php

use App\Controller\MyController;
use Symfony\Component\Config\FileLocator;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Loader\YamlFileLoader;

require '../vendor/autoload.php';

$container = new ContainerBuilder();

$fileLocator = new FileLocator(__DIR__ . '/config');
$loader = new YamlFileLoader($container, $fileLocator);
$loader->load('services.yaml');

$myController = $container->get(MyController::class);

var_dump($myController);

config/services.yaml

services:
    # default configuration for services in *this* file
    _defaults:
        autowire: true      # Automatically injects dependencies in your services.
        autoconfigure: true # Automatically registers your services as commands, event subscribers, etc.
        public: false       # Allows optimizing the container by removing unused services; this also means
                            # fetching services directly from the container via $container->get() won't work.
                            # The best practice is to be explicit about your dependencies anyway.

    # makes classes in src/ available to be used as services
    # this creates a service per class whose id is the fully-qualified class name
    App\:
        resource: '../src/*'
        exclude: '../src/{Entity,Migrations,Tests}'

src/Controller/MyController

<?php

namespace App\Controller;

class MyController {

    public function myAction() {
        echo 'Hello from MyController.';
    }

}

---

更新 1：

使用compile()进行容器编译后

$loader->load('services.yaml');
$container->compile();

我收到以下错误：

( ! ) Fatal error: Uncaught Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: You have requested a non-existent service "App\Controller\MyController". in <my-project-path>/vendor/symfony/dependency-injection/ContainerBuilder.php on line 950
( ! ) Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: You have requested a non-existent service "App\Controller\MyController". in <my-project-path>/vendor/symfony/dependency-injection/ContainerBuilder.php on line 950
Call Stack
#   Time    Memory  Function    Location
1   0.1512  357648  {main}( )   .../index.php:0
2   0.1675  361056  require_once( '<my-project-path>/bootstrap.php' )   .../index.php:7
3   3.5621  2582624 Symfony\Component\DependencyInjection\ContainerBuilder->get( ???, ??? ) .../bootstrap.php:18
4   3.5621  2582624 Symfony\Component\DependencyInjection\ContainerBuilder->doGet( ???, ???, ??? )  .../ContainerBuilder.php:522

我在compile() 调用之后检查了$container->definitions 数组。我意识到所有服务（包括App\Controller\MyController）都保存在compile()之前的定义列表中，编译过程从数组中删除了这些服务。

更多：在$compiler->passConfig->log 我找到了这些条目（在编译步骤之后）：

[0] string  "Symfony\Component\DependencyInjection\Compiler\RemovePrivateAliasesPass: Removed service "Psr\Container\ContainerInterface"; reason: private alias."
[1] string  "Symfony\Component\DependencyInjection\Compiler\RemovePrivateAliasesPass: Removed service "Symfony\Component\DependencyInjection\ContainerInterface"; reason: private alias."
[2] string  "Symfony\Component\DependencyInjection\Compiler\InlineServiceDefinitionsPass: Inlined service "App\Service\MyService" to "App\Controller\MyController"."
[3] string  "Symfony\Component\DependencyInjection\Compiler\RemoveUnusedDefinitionsPass: Removed service "App\Controller\MyController"; reason: unused."
[4] string  "Symfony\Component\DependencyInjection\Compiler\RemoveUnusedDefinitionsPass: Removed service "App\Service\MyService"; reason: unused."

Answer 1

我继续设置了一个新项目。

您的设置存在两个问题。

首先你需要在使用之前编译容器：

// bootstrap.php
$loader->load('services.yaml');

$container->compile();

$myController = $container->get(MyController::class);

然后您需要在将控制器服务从容器中拉出之前将其公开：

// services.yaml
App\:
    resource: 'src/*'
    exclude: 'src/{Entity,Migrations,Tests}'

App\Controller\:
    resource: 'src/Controller/*'
    public: true

这基本上就是框架所做的。