未定义管线时，Laravel如何创建404视图

我一直在努力理解《风帽下的拉威尔》，因为就我个人而言，这有助于我学习和记住某些东西是如何工作的。我无法计算出基本的404是如何工作的

我在157上的

illumb\RoutingRouteCollection.php

中尝试了很多var_转储

public function match(Request $request)
{
    $routes = $this->get($request->getMethod());

    // First, we will see if we can find a matching route for this current request
    // method. If we can, great, we can just return it so that it can be called
    // by the consumer. Otherwise we will check for routes with another verb.
    $route = $this->matchAgainstRoutes($routes, $request);

    if (! is_null($route)) {
        return $route->bind($request);
    }

    // If no route was found we will now check if a matching route is specified by
    // another HTTP verb. If it is we will need to throw a MethodNotAllowed and
    // inform the user agent of which HTTP verb it should use for this route.
    $others = $this->checkForAlternateVerbs($request);

    if (count($others) > 0) {
        return $this->getRouteForMethods($request, $others);
    }


    throw new NotFoundHttpException;
}

---

看起来好像输出404视图的一定是NotFoundHttpException，但我不知道如何输出？

Laravel提供了一个默认的

App\Exceptions\Handler

，它实现了一个

render

方法，该方法就是如何将异常转换为HTTP响应的

---

异常处理程序由try-catch块中的

Http/Kernel.php

调用

当找不到页面时，它将抛出

NotFoundHttpException

有中止方法

vendor/laravel/framework/src/light/Foundation

public function abort($code, $message = '', array $headers = [])
{
    if ($code == 404) {
        throw new NotFoundHttpException($message);
    }

    throw new HttpException($code, $message, null, $headers);
}

laravel为错误代码提供了不同的视图：内部

异常/视图

有可用于错误代码的视图

401,403,404,419,429,500,503

现在，在

illumb\Foundation\Exceptions

内部

Handler.php

：renderHttpException方法用于根据异常的状态代码呈现视图

比如：

1） renderHttpException：此方法检查视图是否存在给定的状态代码，然后返回视图

/**
     * Render the given HttpException.
     *
     * @param  \Symfony\Component\HttpKernel\Exception\HttpException  $e
     * @return \Symfony\Component\HttpFoundation\Response
     */
    protected function renderHttpException(HttpException $e)
    {
        $this->registerErrorViewPaths();

        if (view()->exists($view = "errors::{$e->getStatusCode()}")) {
            return response()->view($view, [
                'errors' => new ViewErrorBag,
                'exception' => $e,
            ], $e->getStatusCode(), $e->getHeaders());
        }

        return $this->convertExceptionToResponse($e);
    }

2） RegisterErrorViewPath：此方法将为错误视图注册路径

 /**
     * Register the error template hint paths.
     *
     * @return void
     */
    protected function registerErrorViewPaths()
    {
        $paths = collect(config('view.paths'));

        View::replaceNamespace('errors', $paths->map(function ($path) {
            return "{$path}/errors";
        })->push(__DIR__.'/views')->all());
    }

现在，如果要创建自定义404页面并呈现该页面，请执行以下操作：

内部

app/Exceptions/Handler.php

 public function render($request, Exception $exception)
 {
        if($this->isHttpException($exception)){
            switch ($exception->getStatusCode()) {

                case 404:
                    return view('path-to-custom404-here');
                    break;

            }
        }
        return parent::render($request, $exception);
}