Laravel核心解读Response

前面两节我们分别讲了Laravel的控制器和Request对象，在讲Request对象的那一节我们看了Request对象是如何被创建出来的以及它支持的方法都定义在哪里，讲控制器时我们详细地描述了如何找到Request对应的控制器方法然后执行处理程序的，本节我们就来说剩下的那一部分，控制器方法的执行结果是如何被转换成响应对象Response然后返回给客户端的。

让我们回到Laravel执行路由处理程序返回响应的代码块:

namespace Illuminate/Routing;html' target='_blank'>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; //收集路由和控制器里应用的中间件 $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()}

在讲控制器的那一节里我们已经提到过runRouteWithinStack方法里是最终执行路由处理程序(控制器方法或者闭包处理程序)的地方，通过上面的代码我们也可以看到执行的结果会传递给Router的prepareResponse方法，当程序流返回到runRoute里后又执行了一次prepareResponse方法得到了要返回给客户端的Response对象， 下面我们就来详细看一下prepareResponse方法。

class Router implements RegistrarContract, BindingRegistrar * 通过给定值创建Response对象 * @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);}

在上面的代码中我们看到有三种Response:

通过prepareResponse中的逻辑可以看到，无论路由执行结果返回的是什么值最终都会被Laravel转换为成一个Response对象，而这些对象都是SymfonyComponentHttpFoundationResponse类或者其子类的对象。从这里也就能看出来跟Request一样Laravel的Response也是依赖Symfony框架的HttpFoundation组件来实现的。

我们来看一下SymfonyComponentHttpFoundationResponse的构造方法：

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); $this- setProtocolVersion( 1.0  //设置响应的Content public function setContent($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;}

所以路由处理程序的返回值在创业Response对象时会设置到对象的content属性里，该属性的值就是返回给客户端的响应的响应内容。

生成Response对象后就要执行对象的prepare方法了，该方法定义在Symfony/Component/HttpFoundation/Resposne类中，其主要目的是对Response进行微调使其能够遵从HTTP/1.1协议（RFC 2616）。

namespace Symfony/Component/HttpFoundation;class Response //在响应被发送给客户端之前对其进行修订使其能遵从HTTP/1.1协议 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里针对各种情况设置了相应的response header 比如Content-Type、Content-Length等等这些我们常见的首部字段。

创建并设置完Response后它会流经路由和框架中间件的后置操作，在中间件的后置操作里一般都是对Response进行进一步加工，最后程序流回到Http Kernel那里， Http Kernel会把Response发送给客户端，我们来看一下这部分的代码。

//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; //发送headers到客户端 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; //发送响应内容到客户端 public function sendContent() echo $this- content; return $this;}

send的逻辑就非常好理解了，把之前设置好的那些headers设置到HTTP响应的首部字段里，Content会echo后被设置到HTTP响应的主体实体中。最后PHP会把完整的HTTP响应发送给客户端。

send响应后Http Kernel会执行terminate方法调用terminate中间件里的terminate方法，最后执行应用的termiate方法来结束整个应用生命周期(从接收请求开始到返回响应结束)。

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