Laravel核心解讀 -- Response

時間 2019-11-07

標籤 laravel 核心解讀 response 简体版

原文原文鏈接

Response

前面兩節咱們分別講了Laravel的控制器和Request對象，在講Request對象的那一節咱們看了Request對象是如何被建立出來的以及它支持的方法都定義在哪裏，講控制器時咱們詳細地描述瞭如何找到Request對應的控制器方法而後執行處理程序的，本節咱們就來講剩下的那一部分，控制器方法的執行結果是如何被轉換成響應對象Response而後返回給客戶端的。php

建立Response

讓咱們回到Laravel執行路由處理程序返回響應的代碼塊:html

namespace Illuminate\Routing;
class Router implements RegistrarContract, BindingRegistrar
{     
    protected function runRoute(Request $request, Route $route)
    {
        $request->setRouteResolver(function () use ($route) {
            return $route;
        });

        $this->events->dispatch(new Events\RouteMatched($route, $request));

        return $this->prepareResponse($request,
            $this->runRouteWithinStack($route, $request)
        );
    }
    
    protected function runRouteWithinStack(Route $route, Request $request)
    {
        $shouldSkipMiddleware = $this->container->bound('middleware.disable') &&
                            $this->container->make('middleware.disable') === true;
        //收集路由和控制器裏應用的中間件
        $middleware = $shouldSkipMiddleware ? [] : $this->gatherRouteMiddleware($route);

        return (new Pipeline($this->container))
                    ->send($request)
                    ->through($middleware)
                    ->then(function ($request) use ($route) {
                        return $this->prepareResponse(
                            $request, $route->run()
                        );
                    });
    
    }
}

在講控制器的那一節裏咱們已經提到過runRouteWithinStack方法裏是最終執行路由處理程序(控制器方法或者閉包處理程序)的地方，經過上面的代碼咱們也能夠看到執行的結果會傳遞給Router的prepareResponse方法，當程序流返回到runRoute裏後又執行了一次prepareResponse方法獲得了要返回給客戶端的Response對象，下面咱們就來詳細看一下prepareResponse方法。git

class Router implements RegistrarContract, BindingRegistrar
{
    /**
     * 經過給定值建立Response對象
     *
     * @param  \Symfony\Component\HttpFoundation\Request  $request
     * @param  mixed  $response
     * @return \Illuminate\Http\Response|\Illuminate\Http\JsonResponse
     */
    public function prepareResponse($request, $response)
    {
        return static::toResponse($request, $response);
    }
    
    public static function toResponse($request, $response)
    {
        if ($response instanceof Responsable) {
            $response = $response->toResponse($request);
        }

        if ($response instanceof PsrResponseInterface) {
            $response = (new HttpFoundationFactory)->createResponse($response);
        } elseif (! $response instanceof SymfonyResponse &&
                   ($response instanceof Arrayable ||
                    $response instanceof Jsonable ||
                    $response instanceof ArrayObject ||
                    $response instanceof JsonSerializable ||
                    is_array($response))) {
            $response = new JsonResponse($response);
        } elseif (! $response instanceof SymfonyResponse) {
            $response = new Response($response);
        }

        if ($response->getStatusCode() === Response::HTTP_NOT_MODIFIED) {
            $response->setNotModified();
        }

        return $response->prepare($request);
    }
}

在上面的代碼中咱們看到有三種Response:github

Class Name	Representation
PsrResponseInterface(PsrHttpMessageResponseInterface的別名)	Psr規範中對服務端響應的定義
IlluminateHttpJsonResponse (SymfonyComponentHttpFoundationResponse的子類)	Laravel中對服務端JSON響應的定義
IlluminateHttpResponse (SymfonyComponentHttpFoundationResponse的子類)	Laravel中對普通的非JSON響應的定義

經過prepareResponse中的邏輯能夠看到，不管路由執行結果返回的是什麼值最終都會被Laravel轉換爲成一個Response對象，而這些對象都是SymfonyComponentHttpFoundationResponse類或者其子類的對象。從這裏也就能看出來跟Request同樣Laravel的Response也是依賴Symfony框架的HttpFoundation組件來實現的。cookie

咱們來看一下SymfonyComponentHttpFoundationResponse的構造方法：閉包

namespace Symfony\Component\HttpFoundation;
class Response
{
    public function __construct($content = '', $status = 200, $headers = array())
    {
        $this->headers = new ResponseHeaderBag($headers);
        $this->setContent($content);
        $this->setStatusCode($status);
        $this->setProtocolVersion('1.0');
    }
    //設置響應的Content
    public function setContent($content)
    {
        if (null !== $content && !is_string($content) && !is_numeric($content) && !is_callable(array($content, '__toString'))) {
            throw new \UnexpectedValueException(sprintf('The Response content must be a string or object implementing __toString(), "%s" given.', gettype($content)));
        }

        $this->content = (string) $content;

        return $this;
    }
}

因此路由處理程序的返回值在創業Response對象時會設置到對象的content屬性裏，該屬性的值就是返回給客戶端的響應的響應內容。app

設置Response headers

生成Response對象後就要執行對象的prepare方法了，該方法定義在Symfony\Component\HttpFoundation\Resposne類中，其主要目的是對Response進行微調使其可以聽從HTTP/1.1協議（RFC 2616）。框架

namespace Symfony\Component\HttpFoundation;
class Response
{
    //在響應被髮送給客戶端以前對其進行修訂使其能聽從HTTP/1.1協議
    public function prepare(Request $request)
    {
        $headers = $this->headers;

        if ($this->isInformational() || $this->isEmpty()) {
            $this->setContent(null);
            $headers->remove('Content-Type');
            $headers->remove('Content-Length');
        } else {
            // Content-type based on the Request
            if (!$headers->has('Content-Type')) {
                $format = $request->getRequestFormat();
                if (null !== $format && $mimeType = $request->getMimeType($format)) {
                    $headers->set('Content-Type', $mimeType);
                }
            }

            // Fix Content-Type
            $charset = $this->charset ?: 'UTF-8';
            if (!$headers->has('Content-Type')) {
                $headers->set('Content-Type', 'text/html; charset='.$charset);
            } elseif (0 === stripos($headers->get('Content-Type'), 'text/') && false === stripos($headers->get('Content-Type'), 'charset')) {
                // add the charset
                $headers->set('Content-Type', $headers->get('Content-Type').'; charset='.$charset);
            }

            // Fix Content-Length
            if ($headers->has('Transfer-Encoding')) {
                $headers->remove('Content-Length');
            }

            if ($request->isMethod('HEAD')) {
                // cf. RFC2616 14.13
                $length = $headers->get('Content-Length');
                $this->setContent(null);
                if ($length) {
                    $headers->set('Content-Length', $length);
                }
            }
        }

        // Fix protocol
        if ('HTTP/1.0' != $request->server->get('SERVER_PROTOCOL')) {
            $this->setProtocolVersion('1.1');
        }

        // Check if we need to send extra expire info headers
        if ('1.0' == $this->getProtocolVersion() && false !== strpos($this->headers->get('Cache-Control'), 'no-cache')) {
            $this->headers->set('pragma', 'no-cache');
            $this->headers->set('expires', -1);
        }

        $this->ensureIEOverSSLCompatibility($request);

        return $this;
    }
}

prepare裏針對各類狀況設置了相應的response header 好比Content-Type、Content-Length等等這些咱們常見的首部字段。學習

發送Response

建立並設置完Response後它會流經路由和框架中間件的後置操做，在中間件的後置操做裏通常都是對Response進行進一步加工，最後程序流回到Http Kernel那裏， Http Kernel會把Response發送給客戶端，咱們來看一下這部分的代碼。this

//入口文件public/index.php
$kernel = $app->make(Illuminate\Contracts\Http\Kernel::class);

$response = $kernel->handle(
    $request = Illuminate\Http\Request::capture()
);

$response->send();

$kernel->terminate($request, $response);

namespace Symfony\Component\HttpFoundation;
class Response
{
    public function send()
    {
        $this->sendHeaders();
        $this->sendContent();

        if (function_exists('fastcgi_finish_request')) {
            fastcgi_finish_request();
        } elseif ('cli' !== PHP_SAPI) {
            static::closeOutputBuffers(0, true);
        }

        return $this;
    }
    
    //發送headers到客戶端
    public function sendHeaders()
    {
        // headers have already been sent by the developer
        if (headers_sent()) {
            return $this;
        }

        // headers
        foreach ($this->headers->allPreserveCaseWithoutCookies() as $name => $values) {
            foreach ($values as $value) {
                header($name.': '.$value, false, $this->statusCode);
            }
        }

        // status
        header(sprintf('HTTP/%s %s %s', $this->version, $this->statusCode, $this->statusText), true, $this->statusCode);

        // cookies
        foreach ($this->headers->getCookies() as $cookie) {
            if ($cookie->isRaw()) {
                setrawcookie($cookie->getName(), $cookie->getValue(), $cookie->getExpiresTime(), $cookie->getPath(), $cookie->getDomain(), $cookie->isSecure(), $cookie->isHttpOnly());
            } else {
                setcookie($cookie->getName(), $cookie->getValue(), $cookie->getExpiresTime(), $cookie->getPath(), $cookie->getDomain(), $cookie->isSecure(), $cookie->isHttpOnly());
            }
        }

        return $this;
    }
    
    //發送響應內容到客戶端
    public function sendContent()
    {
        echo $this->content;

        return $this;
    }
}

send的邏輯就很是好理解了，把以前設置好的那些headers設置到HTTP響應的首部字段裏，Content會echo後被設置到HTTP響應的主體實體中。最後PHP會把完整的HTTP響應發送給客戶端。

send響應後Http Kernel會執行terminate方法調用terminate中間件裏的terminate方法，最後執行應用的termiate方法來結束整個應用生命週期(從接收請求開始到返回響應結束)。

本文已經收錄在系列文章Laravel源碼學習裏，歡迎訪問閱讀。