YII源码分析-处理请求过程

本文讲解内容

从请求入口文件开始，到响应组件发送结果给用户浏览器的过程简要分析。

流程分析

从入口文件进入，直接看关键点，分析application的启动流程

$config = require __DIR__.'/../config/web.php';

(new yii\web\Application($config))->run();

首先进入yii\web\Application类
里面没有构造函数，即找到父级类\yii\base\Application

public function __construct($config = [])
{
    // 保存当前启动的application实例，交给Yii::$app
    Yii::$app = $this;
    static::setInstance($this);

    $this->state = self::STATE_BEGIN;

    $this->preInit($config);
    
    // 加载异常处理，这块比较深，后面再扩展。
    $this->registerErrorHandler($config);

    Component::__construct($config);
}

我们看一下static::setInstance($this);指向到了yii\base\Module

public static function setInstance($instance)
{
    // 将当前实例加入Yii::$app->loadedModules['yii\web\Application']数组中
    if ($instance === null) {
        unset(Yii::$app->loadedModules[get_called_class()]);
    } else {
        Yii::$app->loadedModules[get_class($instance)] = $instance;
    }

}

这里主要是后面使用，比如module里，通过self::getInstance()获取App对象，类似于Yii::$app。(可后面再深入)

接下来看$this->preInit($config);
这里是加载配置文件的框架信息，如：设置别名，设置框架路径等等，最重要的是加载默认组件

foreach ($this->coreComponents() as $id => $component) {
    if (!isset($config['components'][$id])) {
        $config['components'][$id] = $component;
    } elseif (is_array($config['components'][$id]) && !isset($config['components'][$id]['class'])) {
        $config['components'][$id]['class'] = $component['class'];
    }
}

再接着是Component::__construct($config);

public function __construct($config = [])
{
    if (!empty($config)) {
        Yii::configure($this, $config);//将配置文件里面的所有配置信息 本地变量化
    }
    $this->init(); // 取出控制器的命名空间(路径)
}

到这里为止，第一部分已经执行完了，开始执行$application->run()

public function run()
{
    try {
        $this->state = self::STATE_BEFORE_REQUEST;
        //加载事件函数的。类似于狗子，后面再深入分析。
        $this->trigger(self::EVENT_BEFORE_REQUEST);

        $this->state = self::STATE_HANDLING_REQUEST;
        // 重中之重-加载控制器
        $response = $this->handleRequest($this->getRequest());

        $this->state = self::STATE_AFTER_REQUEST;

        $this->trigger(self::EVENT_AFTER_REQUEST);//加载事件函数

        $this->state = self::STATE_SENDING_RESPONSE;

        $response->send();//将页面内容输出

        $this->state = self::STATE_END;

        return $response->exitStatus;

    } catch (ExitException $e) {
        $this->end($e->statusCode, isset($response) ? $response : null);
        return $e->statusCode;
    }
}

我们来看下$response = $this->handleRequest($this->getRequest());

public function handleRequest($request)
    {
        if (empty($this->catchAll)) {
            try {
                list($route, $params) = $request->resolve();
            } catch (UrlNormalizerRedirectException $e) {
                $url = $e->url;
                if (is_array($url)) {
                    if (isset($url[0])) {
                        // ensure the route is absolute
                        $url[0] = '/' . ltrim($url[0], '/');
                    }
                    $url += $request->getQueryParams();
                }

                return $this->getResponse()->redirect(Url::to($url, $e->scheme), $e->statusCode);
            }
        } else {
            $route = $this->catchAll[0];
            $params = $this->catchAll;
            unset($params[0]);
        }
        try {
            Yii::debug("Route requested: '$route'", __METHOD__);
            $this->requestedRoute = $route;
            $result = $this->runAction($route, $params);
            if ($result instanceof Response) {
                return $result;
            }

            $response = $this->getResponse();
            if ($result !== null) {
                $response->data = $result;
            }

            return $response;
        } catch (InvalidRouteException $e) {
            throw new NotFoundHttpException(Yii::t('yii', 'Page not found.'), $e->getCode(), $e);
        }
    }

我们再看看这句指向：\yii\base\Module的runAction

public function runAction($route, $params = [])
    {
        $parts = $this->createController($route);
        if (is_array($parts)) {
            /* @var $controller Controller */
            list($controller, $actionID) = $parts;
            $oldController = Yii::$app->controller;
            Yii::$app->controller = $controller;
            $result = $controller->runAction($actionID, $params);
            if ($oldController !== null) {
                Yii::$app->controller = $oldController;
            }

            return $result;
        }

        $id = $this->getUniqueId();
        throw new InvalidRouteException('Unable to resolve the request "' . ($id === '' ? $route : $id . '/' . $route) . '".');
    }

最后是$response->send();

public function send()
    {
        if ($this->isSent) {
            return;
        }
        $this->trigger(self::EVENT_BEFORE_SEND);
        //取得$response的format  再获得format对象的实例执行  format方法(header设置Content-Type)
        $this->prepare();
        $this->trigger(self::EVENT_AFTER_PREPARE);
        $this->sendHeaders();
        $this->sendContent();
        $this->trigger(self::EVENT_AFTER_SEND);
        $this->isSent = true;
    }

总结

yii给出的运行机制概述和示意图来描述应用是如何处理一个请求的。