今天使用 Lumen 的时候，用到了 Response 类，很奇怪提示：Target [Illuminate\Contracts\Routing\ResponseFactory] is not instantiable.

大概就是说实例不了 Response 类，那怎么解决呢？我们以一个全新的 Lumen 项目来说 

1. 我在 web.php 写了个路由

<?php

/*
|--------------------------------------------------------------------------
| Application Routes
|--------------------------------------------------------------------------
|
| Here is where you can register all of the routes for an application.
| It is a breeze. Simply tell Lumen the URIs it should respond to
| and give it the Closure to call when that URI is requested.
|
*/
use Illuminate\Support\Facades\Response;
$router->get('/', function () use ($router) {return Response::json('123456',200);
});

然后访问这个路由报错如下（也就是我们要解决的错误）：

2. 解决办法

2.1 打开项目根目录下的 bootstrap/app.php

// 找到这两行把注释去掉
 $app->withFacades();  
 $app->register(App\Providers\AppServiceProvider::class);

2.2 找到 项目根目录下的 app/Providers/AppServiceProvider.php

<?php

namespace App\Providers;

use Illuminate\Routing\ResponseFactory;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {}}

在 register 注册 ResponseFactory 修改如下：

<?php

namespace App\Providers;

use Illuminate\Routing\ResponseFactory;
use Illuminate\Support\ServiceProvider;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {$this->app->singleton('Illuminate\Contracts\Routing\ResponseFactory', function ($app)
        {
            return new ResponseFactory($app['Illuminate\Contracts\View\Factory'], 
            $app['Illuminate\Routing\Redirector']);
        });
    }
}

这时候还不行, 我们还需要安装一个 库, 切换到项目根目录 执行 composer 命令：

composer require "illuminate/routing"

库安装完后，我们访问试试：

很简单吧，这样就可以啦~~

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