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Symfony2源码分析——启动过程2

作者:用户 来源:互联网 时间:2017-12-01 12:30:29

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Symfony2源码分析——启动过程2 - 摘要: 本文讲的是Symfony2源码分析——启动过程2,   上一篇分析Symfony2框架源码,探究Symfony2如何完成一个请求的前半部分,前半部分可以理解为Symfony2框架为处理请求做准备工作,包括container生成、缓存、bundls初始化等一些列准备工作(Symfony2源码

  上一篇分析Symfony2框架源码,探究Symfony2如何完成一个请求的前半部分,前半部分可以理解为Symfony2框架为处理请求做准备工作,包括container生成、缓存、bundls初始化等一些列准备工作(Symfony2源码分析——启动过程1)。而这一篇讲的是Symfony2如何根据请求的数据生成Response对象,向客户端返回响应数据。

  在分析前需要了解Symfony2的事件驱动机制:Symfony2事件驱动。

  言归正传,Symfony2请求的工作流程其实是Symfony2内核的事件驱动完成的,下面是Symfony2框架定义好的内核事件:

Symfony2源码分析——启动过程2Symfony2源码分析——启动过程2
final class KernelEvents{    /**     * The REQUEST event occurs at the very beginning of request     * dispatching     *     * This event allows you to create a response for a request before any     * other code in the framework is executed. The event listener method     * receives a Symfony/Component/HttpKernel/Event/GetResponseEvent     * instance.     *     * @var string     *     * @api     */    const REQUEST = 'kernel.request';    /**     * The EXCEPTION event occurs when an uncaught exception appears     *     * This event allows you to create a response for a thrown exception or     * to modify the thrown exception. The event listener method receives     * a Symfony/Component/HttpKernel/Event/GetResponseForExceptionEvent     * instance.     *     * @var string     *     * @api     */    const EXCEPTION = 'kernel.exception';    /**     * The VIEW event occurs when the return value of a controller     * is not a Response instance     *     * This event allows you to create a response for the return value of the     * controller. The event listener method receives a     * Symfony/Component/HttpKernel/Event/GetResponseForControllerResultEvent     * instance.     *     * @var string     *     * @api     */    const VIEW = 'kernel.view';    /**     * The CONTROLLER event occurs once a controller was found for     * handling a request     *     * This event allows you to change the controller that will handle the     * request. The event listener method receives a     * Symfony/Component/HttpKernel/Event/FilterControllerEvent instance.     *     * @var string     *     * @api     */    const CONTROLLER = 'kernel.controller';    /**     * The RESPONSE event occurs once a response was created for     * replying to a request     *     * This event allows you to modify or replace the response that will be     * replied. The event listener method receives a     * Symfony/Component/HttpKernel/Event/FilterResponseEvent instance.     *     * @var string     *     * @api     */    const RESPONSE = 'kernel.response';    /**     * The TERMINATE event occurs once a response was sent     *     * This event allows you to run expensive post-response jobs.     * The event listener method receives a     * Symfony/Component/HttpKernel/Event/PostResponseEvent instance.     *     * @var string     */    const TERMINATE = 'kernel.terminate';    /**     * The FINISH_REQUEST event occurs when a response was generated for a request.     *     * This event allows you to reset the global and environmental state of     * the application, when it was changed during the request.     *     * @var string     */    const FINISH_REQUEST = 'kernel.finish_request';}

  我们可以编写事件监听器,监听相应的内核事件,在Symfony2触发该事件的时候,相应的事件监听器就会执行。监听和唤醒形象的描述,就像,你(事件监听器)参加校运会,去大会(Symfony2)登记(监听)参加50米短跑(事件),当50米短跑比赛开始了(事件被触发),那你就奔跑吧(监听器执行,其实就是一个执行函数,函数完成什么工作就取决于你的需求了),少年。

  Symfony2的内核事件处理流程大部分工作都在HttpKernel::handleRaw方法中:

 1     private function handleRaw(Request $request, $type = self::MASTER_REQUEST) 2     { 3         $this->requestStack->push($request); 4  5         // request 6         // 初始化事件,事件对象会被传递给监听器,所以事件可以说是一个信息的载体,事件内存放着监听器感兴趣的数据。 7         $event = new GetResponseEvent($this, $request, $type); 8         // 触发kernel.request事件,后续详细讲解EventDispatcher::dispatch方法的实现, 9         // 这里我们需要知道的是,dispatcher把$event传递给所有监听了kernel.request事件的监听器,监听器将会执行。10         // kernel.request事件发生在controller执行之前,我们可以在这一步奏完成路由解析等为controller执行提供准备数据,11         // 在这个过程允许我们直接生成Response对象,向客户端输出数据,那么controller就不会被执行了。12         $this->dispatcher->dispatch(KernelEvents::REQUEST, $event);13 14         // 如果我们在kernel.request事件生成了Response对象(响应数据),那么就跳过kernel.controller、kernel.view事件、15         // controller也会被跳过,直接执行kernel.response事件。16         if ($event->hasResponse()) {17             return $this->filterResponse($event->getResponse(), $request, $type);18         }19 20         // load controller21         // 根据路由规则返回 一个对象或者数组或者字符串 ,如果$controller是一个数组,$controller[0]是存放的是要执行的controller对象,22         // $controller[0]存放的是controller对象执行的方法,即action,方法的参数没有保存在$controller数组中;23         // 如果$controller是对象,那么该对象就实现了__invoke 方法;24         // 如果$controller是字符串,那么$controller就是要运行的函数的函数名。25         // 图2是$controller的一个var_dump例子26         if (false === $controller = $this->resolver->getController($request)) {27             throw new NotFoundHttpException(sprintf('Unable to find the controller for path "%s". Maybe you forgot to add the matching route in your routing configuration?', $request->getPathInfo()));28         }29 30         $event = new FilterControllerEvent($this, $controller, $request, $type);31         // 触发kernel.controller事件,这个事件发生在controller执行前。我们可以通过监听这个事件在controller执行前修改controller,32         // 或者完成一些动作。33         $this->dispatcher->dispatch(KernelEvents::CONTROLLER, $event);34         $controller = $event->getController();35 36         // controller arguments37         // 从request对象中获取controller方法的参数38         $arguments = $this->resolver->getArguments($request, $controller);39 40         // call controller41         // 执行controller42         $response = call_user_func_array($controller, $arguments);43 44         // view45         // 如果$response不是Response对象,那么kernel.view事件就会触发,监听kernel.view事件的监听器通过$response值生成Response对象。46         if (!$response instanceof Response) {47             $event = new GetResponseForControllerResultEvent($this, $request, $type, $response);48             $this->dispatcher->dispatch(KernelEvents::VIEW, $event);49 50             if ($event->hasResponse()) {51                 $response = $event->getResponse();52             }53 54             if (!$response instanceof Response) {55                 $msg = sprintf('The controller must return a response (%s given).', $this->varToString($response));56 57                 // the user may have forgotten to return something58                 if (null === $response) {59                     $msg .= ' Did you forget to add a return statement somewhere in your controller?';60                 }61                 throw new /LogicException($msg);62             }63         }64 65         // 触发kernel.response事件,在向客户端输出Response对象前,我们可以对Response对象进行修改,66         // 例如修改response头部,设置缓存、压缩输出数据等。67 68         // 接着触发kernel.finish_request事件,把当前请求从请求栈中弹出,当前请求就完成。69         return $this->filterResponse($response, $request, $type);70 71         // 千万别忘记了,filterResponse执行完后,Symfony2内核事件处理流程还有最后一步,位于app_dev.php[app.php]最后一行,72         // $kernel->terminate($request, $response);这个方法触发kernel.terminate事件,此时,Symfony2已经响应了客户端的请求,73         // 向客户端输出了Response对象。监听kernel.terminate事件的监听器,主要是为了完成一些耗时的操作,操作的结果不需要返回给74         // 客户端的,例如邮件发送、图片压缩等等。75         // 到这里,Symfony2的整个流程就走完了。76     }
HttpKernel::filterResponse方法和HttpKernel::finishRequest方法:
Symfony2源码分析——启动过程2Symfony2源码分析——启动过程2
 1     private function filterResponse(Response $response, Request $request, $type) 2     { 3         $event = new FilterResponseEvent($this, $request, $type, $response); 4  5         $this->dispatcher->dispatch(KernelEvents::RESPONSE, $event); 6  7         $this->finishRequest($request, $type); 8  9         return $event->getResponse();10     }11 12     /**13      * Publishes the finish request event, then pop the request from the stack.14      *15      * Note that the order of the operations is important here, otherwise16      * operations such as {@link RequestStack::getParentRequest()} can lead to17      * weird results.18      *19      * @param Request $request20      * @param int     $type21      */22     private function finishRequest(Request $request, $type)23     {24         $this->dispatcher->dispatch(KernelEvents::FINISH_REQUEST, new FinishRequestEvent($this, $request, $type));25         $this->requestStack->pop();26     }

Symfony2源码分析——启动过程2

图2

Symfony2框架的事件分发机制的核心代码:

 1     public function dispatch($eventName, Event $event = null) 2     { 3         if (null === $event) { 4             $event = new Event(); 5         } 6  7         $event->setDispatcher($this); 8         $event->setName($eventName); 9 10         if (!isset($this->listeners[$eventName])) {11             return $event;12         }13 14         // $eventName即:KernelEvents::REQUEST、KernelEvents::CONTROLLER、KernelEvents::VIEW、KernelEvents::RESPONSE、KernelEvents::TERMINATE等15         // getListeners返回所有监听$eventName事件的监听器16         $this->doDispatch($this->getListeners($eventName), $eventName, $event);17 18         return $event;19     }20 21     protected function doDispatch($listeners, $eventName, Event $event)22     {23         // 监听器执行24         foreach ($listeners as $listener) {25             call_user_func($listener, $event, $eventName, $this);26             // 如果其中一个监听器把$event的propagationStopped属性设置为true,那么表示$eventName这一事件终止执行,27             // 事件不会往$listeners里尚未执行的监听器传递该事件。28             if ($event->isPropagationStopped()) {29                 break;30             }31         }32     }

 

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