标签： laravel 源码分析 Pipeline 中间件
在我们了解了 Pipeline 的源码及工作过程后（见文章Laravel 源码分析---Pineline），我们来看一下框架中使用 Pipeline 实现中间件功能的代码。
框架中间件使用概述。
在 laravel 框架中中间件的配置主要有两个地方，一个是在 App\Http\Kernel 类中进行配置，一个是在路由设置的时候进行配置。所以 laravel 框架中有两处管理与使用中间件的地方，一个是由 Illuminate\Foundation\Http\Kernel 类进行管理，在类中 sendRequestThroughRouter 方法使用；另一个是在 Illuminate\Routing\Router 类中进行管理，由 runRouteWithinStack 方法使用。接下来我们分别看这两处和中间件的管理与使用相关的代码。
Kernel 类对中间件的管理与使用
在使用 laravel 框架的过程中，我们会在 App\Http\Kernel 类中配置我们全局生效的中间件，我们先来看一下框架在此处的默认配置代码
namespace App\Http;
use Illuminate\Foundation\Http\Kernel as HttpKernel;
class Kernel extends HttpKernel
{
/**
* The application's global HTTP middleware stack.
*
* These middleware are run during every request to your application.
* 每个请求都会经过的中间件，全局生效的中间件
* @var array
*/
protected $middleware = [
\Illuminate\Foundation\Http\Middleware\CheckForMaintenanceMode::class,
];
/**
* The application's route middleware groups.
* 应用中路由的中间件组
* @var array
*/
protected $middlewareGroups = [
'web' => [
\App\Http\Middleware\EncryptCookies::class,
\Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse::class,
\Illuminate\Session\Middleware\StartSession::class,
\Illuminate\View\Middleware\ShareErrorsFromSession::class,
\App\Http\Middleware\VerifyCsrfToken::class,
\Illuminate\Routing\Middleware\SubstituteBindings::class,
],
'api' => [
'throttle:60,1',
'bindings',
],
];
/**
* The application's route middleware.
*
* These middleware may be assigned to groups or used individually.
* 路由中可能会用到的中间件的简化别名
* @var array
*/
protected $routeMiddleware = [
'auth' => \Illuminate\Auth\Middleware\Authenticate::class,
'auth.basic' => \Illuminate\Auth\Middleware\AuthenticateWithBasicAuth::class,
'bindings' => \Illuminate\Routing\Middleware\SubstituteBindings::class,
'can' => \Illuminate\Auth\Middleware\Authorize::class,
'guest' => \App\Http\Middleware\RedirectIfAuthenticated::class,
'throttle' => \Illuminate\Routing\Middleware\ThrottleRequests::class,
];
}
我们看到这个类继承自 Illuminate\Foundation\Http\Kernel 类，主要进行中间件的配置。而其父类主要负责中间件的管理与使用，我们来看其相应源码。
namespace Illuminate\Foundation\Http;
use Illuminate\Routing\Router;
use Illuminate\Routing\Pipeline;
use Illuminate\Contracts\Foundation\Application;
use Illuminate\Contracts\Http\Kernel as KernelContract;
class Kernel implements KernelContract
{
/**
* The application implementation.
*
* @var \Illuminate\Contracts\Foundation\Application
*/
protected $app;
/**
* The router instance.
* 框架路由类的实例，管理框架的中所有配置的路由，实现供框架使用的路由功能
* @var \Illuminate\Routing\Router
*/
protected $router;
/**
* The application's middleware stack.
* 应用全局生效的中间件队列
* @var array
*/
protected $middleware = [];
/**
* The application's route middleware groups.
* 应用的路由中间件组
* @var array
*/
protected $middlewareGroups = [];
/**
* The application's route middleware.
* 路由中可能会用到的中间件的简化别名
* @var array
*/
protected $routeMiddleware = [];
/**
* The priority-sorted list of middleware.
* Forces the listed middleware to always be in the given order.
* 中间件的优先级，强制下面这些中间件按照给定的顺序执行
* @var array
*/
protected $middlewarePriority = [
\Illuminate\Session\Middleware\StartSession::class,
\Illuminate\View\Middleware\ShareErrorsFromSession::class,
\Illuminate\Auth\Middleware\Authenticate::class,
\Illuminate\Session\Middleware\AuthenticateSession::class,
\Illuminate\Routing\Middleware\SubstituteBindings::class,
\Illuminate\Auth\Middleware\Authorize::class,
];
/**
* Create a new HTTP kernel instance.
* 创建一个 HTTP kernel 类的实例
* @param \Illuminate\Contracts\Foundation\Application $app
* @param \Illuminate\Routing\Router $router
* @return void
*/
public function __construct(Application $app, Router $router)
{
$this->app = $app;
$this->router = $router;
//给路由设置某些中间件的优先级
$router->middlewarePriority = $this->middlewarePriority;
//设置路由可能会用到的中间件组
foreach ($this->middlewareGroups as $key => $middleware) {
$router->middlewareGroup($key, $middleware);
}
//设置路由可能会用到的中间件及对应的简化别名
foreach ($this->routeMiddleware as $key => $middleware) {
$router->middleware($key, $middleware);
}
}
/**
* Handle an incoming HTTP request.
* 执行一个 http 请求
* @param \Illuminate\Http\Request $request
* @return \Illuminate\Http\Response
*/
public function handle($request)
{
try {
...
//将请求通过中间件分发给路由
$response = $this->sendRequestThroughRouter($request);
} catch (Exception $e) {
$this->reportException($e);
$response = $this->renderException($request, $e);
} catch (Throwable $e) {
$this->reportException($e = new FatalThrowableError($e));
$response = $this->renderException($request, $e);
}
$this->app['events']->fire('kernel.handled', [$request, $response]);
return $response;
}
/**
* Send the given request through the middleware / router.
* 发送 $request，通过全局中间件，并分发给路由
* @param \Illuminate\Http\Request $request
* @return \Illuminate\Http\Response
*/
protected function sendRequestThroughRouter($request)
{
...
//根绝全局配置的中间件，设置中间件任务队列并执行
//$this->app->shouldSkipMiddleware() 是否跳过中间件
//$this->dispatchToRouter() 将请求分发给路由
return (new Pipeline($this->app))
->send($request)
->through($this->app->shouldSkipMiddleware() ? [] : $this->middleware)
->then($this->dispatchToRouter());
}
/**
* Get the route dispatcher callback.
* 返回路由分发器的回调函数
* @return \Closure
*/
protected function dispatchToRouter()
{
return function ($request) {
$this->app->instance('request', $request);
//根据路由的配置分发请求，
//并返回相应路由配置的控制器和方法执行后的响应
return $this->router->dispatch($request);
};
}
}
我们看到，Kernel 主要是配置全局中间件和路由中间件，管理和执行全局中间件。当请求通过全局中间件后，将请求分发到路由。接下来我们来看路由对请求的分发，以及其对路由中间件的管理和执行。
Router 类对路由中间件的管理与使用
在 laravel 框架中，路由系统是其非常重要的功能之一，路由中间件的配置和是由路由系统中的 Illuminate\Routing\Router 来管理的，其也是框架路由系统的门面类，向外提供路由系统所需要提供的方法。我们来看一下 Router 类下和路由管理与中间件管理相关的功能。
namespace Illuminate\Routing;
use Closure;
use Illuminate\Http\Request;
use Illuminate\Http\Response;
use Illuminate\Support\Collection;
use Symfony\Bridge\PsrHttpMessage\Factory\HttpFoundationFactory;
use Illuminate\Contracts\Routing\Registrar as RegistrarContract;
use Symfony\Component\HttpFoundation\Response as SymfonyResponse;
class Router implements RegistrarContract
{
/**
* The IoC container instance.
* Ioc 容器实例
* @var \Illuminate\Container\Container
*/
protected $container;
/**
* The route collection instance.
* 用户配置的所有路由的集合
* @var \Illuminate\Routing\RouteCollection
*/
protected $routes;
/**
* The currently dispatched route instance.
* 当前请求所匹配的路由实例
* @var \Illuminate\Routing\Route
*/
protected $current;
/**
* The request currently being dispatched.
* 传入的被分发的请求
* @var \Illuminate\Http\Request
*/
protected $currentRequest;
/**
* All of the short-hand keys for middlewares.
* 路由系统中存在简写别名的中间件
* @var array
*/
protected $middleware = [];
/**
* All of the middleware groups.
* 路由系统所有会用到的中间件组
* @var array
*/
protected $middlewareGroups = [];
/**
* The priority-sorted list of middleware.
* Forces the listed middleware to always be in the given order.
* 中间件的优先级，强制下面这些中间件按照给定的顺序执行
* @var array
*/
public $middlewarePriority = [];
/**
*
* Dispatch the request to the application.
* 分发请求到某个配置的路由
* @param \Illuminate\Http\Request $request
* @return \Illuminate\Http\Response
*/
public function dispatch(Request $request)
{
$this->currentRequest = $request;
return $this->dispatchToRoute($request);
}
/**
* Dispatch the request to a route and return the response.
* 分发请求到某个路由，并返回执行请求得到的响应
* @param \Illuminate\Http\Request $request
* @return mixed
*/
public function dispatchToRoute(Request $request)
{
//首先，在用户配置的路由组里面找到匹配请求的路由
$route = $this->findRoute($request);
//在 $request 设置路由 resolver
//以便路由上的中间件拥有访问此路由实例的接口
$request->setRouteResolver(function () use ($route) {
return $route;
});
...
//运行路由的中间件，让 $request 通过 $route 配置的中间件
$response = $this->runRouteWithinStack($route, $request);
//根据 $request 和 $response，准备 $response 响应对象
return $this->prepareResponse($request, $response);
}
/**
* 运行路由的中间件，让 $request 通过 $route 配置的中间件
* @param \Illuminate\Routing\Route $route
* @param \Illuminate\Http\Request $request
* @return mixed
*/
protected function runRouteWithinStack(Route $route, Request $request)
{
//是否应该跳过中间件
$shouldSkipMiddleware = $this->container->bound('middleware.disable') &&
$this->container->make('middleware.disable') === true;
$middleware = $shouldSkipMiddleware ? [] : $this->gatherRouteMiddleware($route);
//让请求 $request 通过 $route 的中间件，
//并最终返回路由执行请求的响应
return (new Pipeline($this->container))
->send($request)
->through($middleware)
->then(function ($request) use ($route) {
return $this->prepareResponse(
$request, $route->run($request)
);
});
}
/**
* Gather the middleware for the given route.
* 获取解析过的路由的中间件
* @param \Illuminate\Routing\Route $route
* @return array
*/
public function gatherRouteMiddleware(Route $route)
{
//获取路由的中间件并解析
$middleware = collect($route->gatherMiddleware())->map(function ($name) {
return (array) $this->resolveMiddlewareClassName($name);
})->flatten();
//对中间件按照指定优先级排序
return $this->sortMiddleware($middleware);
}
/**
* Resolve the middleware name to a class name(s) preserving passed parameters.
* 根据 $name 解析出来中间件的信息（保留传入中间件的参数）
* $name 可能为匿名函数（直接返回）
* $name 为 $this->middleware 中某个中间件名字
* $name 为 $this->middlewareGroups 中的某个中间件组名字
* $name 为普通字符串
* @param string $name
* @return string|array
*/
public function resolveMiddlewareClassName($name)
{
$map = $this->middleware;
if ($name instanceof Closure) {
return $name;
} elseif (isset($map[$name]) && $map[$name] instanceof Closure) {
return $map[$name];
} elseif (isset($this->middlewareGroups[$name])) {
//解析中间件组
return $this->parseMiddlewareGroup($name);
} else {
// $name 为字符串，解析字符串中的中间件信息
list($name, $parameters) = array_pad(explode(':', $name, 2), 2, null);
return (isset($map[$name]) ? $map[$name] : $name).
(! is_null($parameters) ? ':'.$parameters : '');
}
}
/**
* Parse the middleware group and format it for usage.
* 根据中间组信息，解析其中的中间件
* @param string $name
* @return array
*/
protected function parseMiddlewareGroup($name)
{
$results = [];
foreach ($this->middlewareGroups[$name] as $middleware) {
//递归解析中间件组
if (isset($this->middlewareGroups[$middleware])) {
$results = array_merge(
$results, $this->parseMiddlewareGroup($middleware)
);
continue;
}
list($middleware, $parameters) = array_pad(
explode(':', $middleware, 2), 2, null
);
if (isset($this->middleware[$middleware])) {
$middleware = $this->middleware[$middleware];
}
$results[] = $middleware.($parameters ? ':'.$parameters : '');
}
return $results;
}
/**
* Sort the given middleware by priority.
* 按照指定优先级对中间件进行排序
* @param \Illuminate\Support\Collection $middlewares
* @return array
*/
protected function sortMiddleware(Collection $middlewares)
{
return (new SortedMiddleware($this->middlewarePriority, $middlewares))->all();
}
/**
* Find the route matching a given request.
* 在用户配置的路由集合（$this->routes）中匹配符合请求 $request 的路由
* @param \Illuminate\Http\Request $request
* @return \Illuminate\Routing\Route
*/
protected function findRoute($request)
{
$this->current = $route = $this->routes->match($request);
$this->container->instance('Illuminate\Routing\Route', $route);
return $route;
}
/**
* Register a short-hand name for a middleware.
* 为中间件 $class 注册一个简写的名字
* @param string $name
* @param string $class
* @return $this
*/
public function middleware($name, $class)
{
$this->middleware[$name] = $class;
return $this;
}
/**
* Register a group of middleware.
* 注册一个中间件组
* @param string $name
* @param array $middleware
* @return $this
*/
public function middlewareGroup($name, array $middleware)
{
$this->middlewareGroups[$name] = $middleware;
return $this;
}
}
我们看到关于请求 $request 的分发任务进来后（Kernel 类中 $this->router->dispatch($request) 方法的调用），Router 类首先在配置的路由集合中找到匹配 $request 的路由，并解析出匹配到的路由的中间件，让请求 $request 通过中间件，最终返回路由执行请求的响应。
总结
Pipeline 和 Pipeline 在中间件中的应用是 laravel 框架中很重要的一块功能，理解这部分代码的实现，对我们理解框架的设计思想具有很重要的作用。
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