Lumen开启StartSession中间件后，报错：Response需要为Object，但是得到的是String

通过以下命令刚安装的Lumen：

<code>composer create-project laravel/lumen --prefer-dist
</code>

做了以下修改：
1、修改 .env 文件

<code>APP_KEY=iMXwF1A6Vdbg5V8bYzuNbqv0HX6nH9Cd
SESSION_DRIVER=file
</code>

2、修改 bootstrap/app.php 文件，取消以下代码的注释屏蔽：

<code>Dotenv::load(__DIR__.'/../');

$app->withFacades();
$app->withEloquent();

 $app->middleware([
     // Illuminate\Cookie\Middleware\EncryptCookies::class,
     // Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse::class,
      Illuminate\Session\Middleware\StartSession::class,
     // Illuminate\View\Middleware\ShareErrorsFromSession::class,
     // Laravel\Lumen\Http\Middleware\VerifyCsrfToken::class,
 ]);
</code>

出现以下错误提示：

<code>Whoops, looks like something went wrong.

1/1
ErrorException in StartSession.php line 171:
Argument 1 passed to Illuminate\Session\Middleware\StartSession::addCookieToResponse() must be an instance of Symfony\Component\HttpFoundation\Response, string given, called in F:\upupw\vhosts\lumen\vendor\illuminate\session\Middleware\StartSession.php on line 71 and defined
in StartSession.php line 171
at Application->Laravel\Lumen\{closure}('4096', 'Argument 1 passed to Illuminate\Session\Middleware\StartSession::addCookieToResponse() must be an instance of Symfony\Component\HttpFoundation\Response, string given, called in F:\upupw\vhosts\lumen\vendor\illuminate\session\Middleware\StartSession.php on line 71 and defined', 'F:\upupw\vhosts\lumen\vendor\illuminate\session\Middleware\StartSession.php', '171', array()) in StartSession.php line 171
at StartSession->addCookieToResponse('  <title>Lumen</title> <link href="//fonts.googleapis.com/css?family=Lato:100" rel="stylesheet" type="text/css"> <style> body { margin: 0; padding: 0; width: 100%; height: 100%; color: #B0BEC5; display: table; font-weight: 100; font-family: 'Lato'; } .container { text-align: center; display: table-cell; vertical-align: middle; } .content { text-align: center; display: inline-block; } .title { font-size: 96px; margin-bottom: 40px; } .quote { font-size: 24px; } </style>   

<div class="container"> <div class="content"> <div class="title">Lumen.</div> </div> </div>

   ', object(Store)) in StartSession.php line 71
at StartSession->handle(object(Request), object(Closure))
at call_user_func_array(array(object(StartSession), 'handle'), array(object(Request), object(Closure))) in Pipeline.php line 124
at Pipeline->Illuminate\Pipeline\{closure}(object(Request))
at call_user_func(object(Closure), object(Request)) in Pipeline.php line 103
at Pipeline->then(object(Closure)) in Application.php line 1354
at Application->sendThroughPipeline(array('Illuminate\Session\Middleware\StartSession'), object(Closure)) in Application.php line 1135
at Application->dispatch(null) in Application.php line 1073
at Application->run() in index.php line 28
</code>

然后找到vendor/illuminate/session/Middleware/StartSession.php文件，添加了调试信息：
修改 handle() 方法如下：

<code>    public function handle(Request $request, Closure $next)
    {
        $this->sessionHandled = true;

        // If a session driver has been configured, we will need to start the session here
        // so that the data is ready for an application. Note that the Laravel sessions
        // do not make use of PHP "native" sessions in any way since they are crappy.
        if ($this->sessionConfigured()) {
            $session = $this->startSession($request);

            $request->setSession($session);
        }

        $response = $next($request);
        echo gettype($response) . '<br>';
        // Again, if the session has been configured we will need to close out the session
        // so that the attributes may be persisted to some storage medium. We will also
        // add the session identifier cookie to the application response headers now.
        if ($this->sessionConfigured()) {
            $this->storeCurrentUrl($request, $session);

            $this->collectGarbage($session);
            echo gettype($response) . '<br>';
            $this->addCookieToResponse($response, $session);
        }

        return $response;
    }
</code>

输出显示：

<code>string
string
</code>

错误信息说 addCookieToResponse 方法第一个参数 需要 Response实例，而的到是却是String，不知如何解决@@

回复内容：

通过以下命令刚安装的Lumen：

<code>composer create-project laravel/lumen --prefer-dist
</code>

做了以下修改：
1、修改 .env 文件

<code>APP_KEY=iMXwF1A6Vdbg5V8bYzuNbqv0HX6nH9Cd
SESSION_DRIVER=file
</code>

2、修改 bootstrap/app.php 文件，取消以下代码的注释屏蔽：

<code>Dotenv::load(__DIR__.'/../');

$app->withFacades();
$app->withEloquent();

 $app->middleware([
     // Illuminate\Cookie\Middleware\EncryptCookies::class,
     // Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse::class,
      Illuminate\Session\Middleware\StartSession::class,
     // Illuminate\View\Middleware\ShareErrorsFromSession::class,
     // Laravel\Lumen\Http\Middleware\VerifyCsrfToken::class,
 ]);
</code>

出现以下错误提示：

<code>Whoops, looks like something went wrong.

1/1
ErrorException in StartSession.php line 171:
Argument 1 passed to Illuminate\Session\Middleware\StartSession::addCookieToResponse() must be an instance of Symfony\Component\HttpFoundation\Response, string given, called in F:\upupw\vhosts\lumen\vendor\illuminate\session\Middleware\StartSession.php on line 71 and defined
in StartSession.php line 171
at Application->Laravel\Lumen\{closure}('4096', 'Argument 1 passed to Illuminate\Session\Middleware\StartSession::addCookieToResponse() must be an instance of Symfony\Component\HttpFoundation\Response, string given, called in F:\upupw\vhosts\lumen\vendor\illuminate\session\Middleware\StartSession.php on line 71 and defined', 'F:\upupw\vhosts\lumen\vendor\illuminate\session\Middleware\StartSession.php', '171', array()) in StartSession.php line 171
at StartSession->addCookieToResponse('  <title>Lumen</title> <link href="//fonts.googleapis.com/css?family=Lato:100" rel="stylesheet" type="text/css"> <style> body { margin: 0; padding: 0; width: 100%; height: 100%; color: #B0BEC5; display: table; font-weight: 100; font-family: 'Lato'; } .container { text-align: center; display: table-cell; vertical-align: middle; } .content { text-align: center; display: inline-block; } .title { font-size: 96px; margin-bottom: 40px; } .quote { font-size: 24px; } </style>   

<div class="container"> <div class="content"> <div class="title">Lumen.</div> </div> </div>

   ', object(Store)) in StartSession.php line 71
at StartSession->handle(object(Request), object(Closure))
at call_user_func_array(array(object(StartSession), 'handle'), array(object(Request), object(Closure))) in Pipeline.php line 124
at Pipeline->Illuminate\Pipeline\{closure}(object(Request))
at call_user_func(object(Closure), object(Request)) in Pipeline.php line 103
at Pipeline->then(object(Closure)) in Application.php line 1354
at Application->sendThroughPipeline(array('Illuminate\Session\Middleware\StartSession'), object(Closure)) in Application.php line 1135
at Application->dispatch(null) in Application.php line 1073
at Application->run() in index.php line 28
</code>

然后找到vendor/illuminate/session/Middleware/StartSession.php文件，添加了调试信息：
修改 handle() 方法如下：

<code>    public function handle(Request $request, Closure $next)
    {
        $this->sessionHandled = true;

        // If a session driver has been configured, we will need to start the session here
        // so that the data is ready for an application. Note that the Laravel sessions
        // do not make use of PHP "native" sessions in any way since they are crappy.
        if ($this->sessionConfigured()) {
            $session = $this->startSession($request);

            $request->setSession($session);
        }

        $response = $next($request);
        echo gettype($response) . '<br>';
        // Again, if the session has been configured we will need to close out the session
        // so that the attributes may be persisted to some storage medium. We will also
        // add the session identifier cookie to the application response headers now.
        if ($this->sessionConfigured()) {
            $this->storeCurrentUrl($request, $session);

            $this->collectGarbage($session);
            echo gettype($response) . '<br>';
            $this->addCookieToResponse($response, $session);
        }

        return $response;
    }
</code>

输出显示：

<code>string
string
</code>

错误信息说 addCookieToResponse 方法第一个参数 需要 Response实例，而的到是却是String，不知如何解决@@

抱歉，刚刚下班回来才看到。

如果直接在路由的回调中返回的确实是 String，如果是在控制器中调用，框架会帮忙把 String 转为 Response 对象。
当然，在路由回调中我们直接也可以转一下。prepareResponse方法参见类 Laravel\Lumen\Application：

<code>php</code><code>$app->get('/', function() use ($app) {
    return $app->prepareResponse($app->welcome());
});
</code>

@Mr_Jing（Lumen 初体验 文章作者）可以麻烦解答下吗？