Laravel中Middleware如何使用
今天就跟大家聊聊有關(guān)Laravel中Middleware如何使用，可能很多人都不太了解，為了讓大家更加了解，小編給大家總結(jié)了以下內(nèi)容，希望大家根據(jù)這篇文章可以有所收獲。
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PHP內(nèi)置函數(shù)array_reverse、array_reduce、call_user_func和call_user_func_array
看Laravel源碼之前，先看下這幾個PHP內(nèi)置函數(shù)的使用。首先array_reverse()函數(shù)比較簡單，倒置數(shù)組，看測試代碼：
$pipes = [ 'Pipe1', 'Pipe2', 'Pipe3', 'Pipe4', 'Pipe5', 'Pipe6', ]; $pipes = array_reverse($pipes); var_dump($pipes); // output array(6) { [0] => string(5) "Pipe6" [1] => string(5) "Pipe5" [2] => string(5) "Pipe4" [3] => string(5) "Pipe3" [4] => string(5) "Pipe2" [5] => string(5) "Pipe1" }array_reduce內(nèi)置函數(shù)主要是用回調(diào)函數(shù)去迭代數(shù)組中每一個值，并且每一次回調(diào)得到的結(jié)果值作為下一次回調(diào)的初始值，***返回最終迭代的值：
/** * @link http://php.net/manual/zh/function.array-reduce.php * @param int $v * @param int $w * * @return int */ function rsum($v, $w) { $v += $w; return $v; } $a = [1, 2, 3, 4, 5]; // 10為初始值 $b = array_reduce($a, "rsum", 10); // ***輸出 (((((10 + 1) + 2) + 3) + 4) + 5) = 25 echo $b . PHP_EOL;call_user_func()是執(zhí)行回調(diào)函數(shù)，并可輸入?yún)?shù)作為回調(diào)函數(shù)的參數(shù)，看測試代碼：
class TestCallUserFunc { public function index($request) { echo $request . PHP_EOL; } } /** * @param $test */ function testCallUserFunc($test) { echo $test . PHP_EOL; } // [$class, $method] call_user_func(['TestCallUserFunc', 'index'], 'pipes'); // 輸出'pipes' // Closure call_user_func(function ($passable) { echo $passable . PHP_EOL; }, 'pipes'); // 輸出'pipes' // function call_user_func('testCallUserFunc' , 'pipes'); // 輸出'pipes'call_user_func_array與call_user_func基本一樣，只不過傳入的參數(shù)是數(shù)組：
class TestCallUserFuncArray { public function index($request) { echo $request . PHP_EOL; } } /** * @param $test */ function testCallUserFuncArray($test) { echo $test . PHP_EOL; } // [$class, $method] call_user_func_array(['TestCallUserFuncArray', 'index'], ['pipes']); // 輸出'pipes' // Closure call_user_func_array(function ($passable) { echo $passable . PHP_EOL; }, ['pipes']); // 輸出'pipes' // function call_user_func_array('testCallUserFuncArray' , ['pipes']); // 輸出'pipes'Middleware源碼解析
了解了幾個PHP內(nèi)置函數(shù)后再去看下Middleware源碼就比較簡單了。Laravel學(xué)習(xí)筆記之IoC Container實例化源碼解析已經(jīng)聊過Application的實例化，得到index.php中的$app變量，即\Illuminate\Foundation\Application的實例化對象。然后繼續(xù)看下index.php的源碼：
/** * @var \App\Http\Kernel $kernel */ $kernel = $app->make(Illuminate\Contracts\Http\Kernel::class); $response = $kernel->handle( $request = Illuminate\Http\Request::capture() ); $response->send(); $kernel->terminate($request, $response);
首先從容器中解析出Kernel對象，對于\App\Http\Kernel對象的依賴:\Illuminate\Foundation\Application和\Illuminate\Routing\Router，容器會自動解析?？聪翶ernel的構(gòu)造函數(shù)：
/** * Create a new HTTP kernel instance. * * @param \Illuminate\Contracts\Foundation\Application $app * @param \Illuminate\Routing\Router $router */ public function __construct(Application $app, Router $router) { $this->app = $app; $this->router = $router; foreach ($this->middlewareGroups as $key => $middleware) { $router->middlewareGroup($key, $middleware); } foreach ($this->routeMiddleware as $key => $middleware) { $router->middleware($key, $middleware); } } // \Illuminate\Routing\Router內(nèi)的方法 public function middlewareGroup($name, array $middleware) { $this->middlewareGroups[$name] = $middleware; return $this; } public function middleware($name, $class) { $this->middleware[$name] = $class; return $this; }構(gòu)造函數(shù)初始化了幾個中間件數(shù)組，$middleware[ ], $middlewareGroups[ ]和$routeMiddleware[ ]，Laravel5.0的時候記得中間件數(shù)組還沒有分的這么細。然后就是Request的實例化：
$request = Illuminate\Http\Request::capture()
這個過程以后再聊吧，不管咋樣，得到了Illuminate\Http\Request對象，然后傳入Kernel中：
/** * Handle an incoming HTTP request. * * @param \Illuminate\Http\Request $request * @return \Illuminate\Http\Response */ public function handle($request) { try { $request->enableHttpMethodParameterOverride(); $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 $response; }主要是sendRequestThroughRouter($request)函數(shù)執(zhí)行了轉(zhuǎn)換操作：把\Illuminate\Http\Request對象轉(zhuǎn)換成了\Illuminate\Http\Response，然后通過Kernel的send()方法發(fā)送給客戶端。同時，順便觸發(fā)了kernel.handled內(nèi)核已處理請求事件。OK，重點關(guān)注下sendRequestThroughRouter($request)方法：
/** * Send the given request through the middleware / router. * * @param \Illuminate\Http\Request $request * @return \Illuminate\Http\Response */ protected function sendRequestThroughRouter($request) { $this->app->instance('request', $request); Facade::clearResolvedInstance('request'); /* 依次執(zhí)行$bootstrappers中每一個bootstrapper的bootstrap()函數(shù),做了幾件準備事情: 1. 環(huán)境檢測 2. 配置加載 3. 日志配置 4. 異常處理 5. 注冊Facades 6. 注冊Providers 7. 啟動服務(wù) protected $bootstrappers = [ 'Illuminate\Foundation\Bootstrap\DetectEnvironment', 'Illuminate\Foundation\Bootstrap\LoadConfiguration', 'Illuminate\Foundation\Bootstrap\ConfigureLogging', 'Illuminate\Foundation\Bootstrap\HandleExceptions', 'Illuminate\Foundation\Bootstrap\RegisterFacades', 'Illuminate\Foundation\Bootstrap\RegisterProviders', 'Illuminate\Foundation\Bootstrap\BootProviders', ];*/ $this->bootstrap(); return (new Pipeline($this->app)) ->send($request) ->through($this->app->shouldSkipMiddleware() ? [] : $this->middleware) ->then($this->dispatchToRouter()); }$this->bootstrap()主要是做了程序初始化工作，以后再聊具體細節(jié)。然后是Pipeline來傳輸Request，Laravel中把Pipeline管道單獨拿出來作為一個service(可看Illuminate/Pipeline文件夾)，說明Pipeline做的事情還是很重要的：主要就是作為Request的傳輸管道，依次通過$middlewares[ ], 或middlewareGroups[ ], 或$routeMiddleware[ ]這些中間件的前置操作，和控制器的某個action或者直接閉包處理得到Response，然后又帶著Reponse依次通過$middlewares[ ], 或middlewareGroups[ ], 或$routeMiddleware[ ]這些中間件的后置操作得到準備就緒的Response，然后通過send()發(fā)送給客戶端。
這個過程有點像汽車工廠的生產(chǎn)一樣，Pipeline是傳送帶，起初Request可能就是個汽車空殼子，經(jīng)過傳送帶旁邊的一個個機械手middleware@before的過濾和操作(如檢查零件剛度是不是合格，殼子尺寸是不是符合要求，給殼子噴個漆或抹個油啥的)，然后進入中央控制區(qū)加個發(fā)動機(Controller@action，或Closure)，然后又繼續(xù)經(jīng)過檢查和附加操作middleware@after(如添加個擋風(fēng)鏡啥的)，然后通過門外等著的火車直接運送到消費者手里send()。在每一步裝配過程中，都需要Service來支持，Service是通過Container來解析{make()}提供的，并且Service是通過ServiceProvider注冊綁定{bind(),singleton(),instance()}到Container中的。
看下Pipeline的send()和through()源碼：
public function send($passable) { $this->passable = $passable; return $this; } public function through($pipes) { $this->pipes = is_array($pipes) ? $pipes : func_get_args(); return $this; }send()傳送的對象是Request，through()所要通過的對象是$middleware[ ]，OK，再看下dispatchToRouter()的源碼直接返回一個Closure：
protected function dispatchToRouter() { return function ($request) { $this->app->instance('request', $request); return $this->router->dispatch($request); }; }然后重點看下then()函數(shù)源碼：
public function then(Closure $destination) { $firstSlice = $this->getInitialSlice($destination); $pipes = array_reverse($this->pipes); // $this->passable = Request對象 return call_user_func( array_reduce($pipes, $this->getSlice(), $firstSlice), $this->passable ); } protected function getInitialSlice(Closure $destination) { return function ($passable) use ($destination) { return call_user_func($destination, $passable); }; }這里假設(shè)$middlewares為(盡管源碼中$middlewares只有一個CheckForMaintenanceMode::class)：
$middlewares = [ CheckForMaintenanceMode::class, AddQueuedCookiesToResponse::class, StartSession::class, ShareErrorsFromSession::class, VerifyCsrfToken::class, ];
先獲得***個slice(這里作者是比作'洋蔥'，一層層的穿過，從一側(cè)穿過到另一側(cè)，比喻倒也形象)并作為array_reduce()的初始值，就像上文中array_reduce()測試例子中的10這個初始值，這個初始值現(xiàn)在是個閉包：
$destination = function ($request) { $this->app->instance('request', $request); return $this->router->dispatch($request); }; $firstSlice = function ($passable) use ($destination) { return call_user_func($destination, $passable); };OK,然后要對$middlewares[ ]進行翻轉(zhuǎn)，為啥要翻轉(zhuǎn)呢?
看過這篇Laravel學(xué)習(xí)筆記之Decorator Pattern文章就會發(fā)現(xiàn)，在Client類利用Decorator Pattern進行依次裝飾的時候，是按照$middlewares[ ]數(shù)組中值倒著new的：
public function wrapDecorator(IMiddleware $decorator) { $decorator = new VerifyCsrfToken($decorator); $decorator = new ShareErrorsFromSession($decorator); $decorator = new StartSession($decorator); $decorator = new AddQueuedCookiesToResponse($decorator); $response = new CheckForMaintenanceMode($decorator); return $response; }這樣才能得到一個符合$middlewares[ ]順序的$response對象：
$response = new CheckForMaintenanceMode( new AddQueuedCookiesToResponse( new StartSession( new ShareErrorsFromSession( new VerifyCsrfToken( new Request() ) ) ) ) );
看下array_reduce()中的迭代回調(diào)函數(shù)getSlice(){這個迭代回調(diào)函數(shù)比作剝洋蔥時獲取每一層洋蔥slice，初始值是$firstSlice}：
protected function getSlice() { return function ($stack, $pipe) { return function ($passable) use ($stack, $pipe) { if ($pipe instanceof Closure) { return call_user_func($pipe, $passable, $stack); } elseif (! is_object($pipe)) { list($name, $parameters) = $this->parsePipeString($pipe); $pipe = $this->container->make($name); $parameters = array_merge([$passable, $stack], $parameters); } else{ $parameters = [$passable, $stack]; } return call_user_func_array([$pipe, $this->method], $parameters); }; }; }返回的是個閉包，仔細看下第二層閉包里的邏輯，這里$middlewares[ ]傳入的是每一個中間件的名字，然后通過容器解析出每一個中間件對象：
$pipe = $this->container->make($name);
并***用call_user_func_array([$class, $method], array $parameters)來調(diào)用這個$class里的$method方法，參數(shù)是$parameters。
Demo
接下來寫個demo看下整個流程。先簡化下getSlice()函數(shù)，這里就默認$pipe傳入的是類名稱(整個demo中所有class都在同一個文件內(nèi))：
// PipelineTest.php // Get the slice in every step. function getSlice() { return function ($stack, $pipe) { return function ($passable) use ($stack, $pipe) { /** * @var Middleware $pipe */ return call_user_func_array([$pipe, 'handle'], [$passable, $stack]); }; }; }再把$middlewares[ ]中五個中間件類寫上，對于前置操作和后置操作做個簡化，直接echo字符串：
// PipelineTest.php <?php interface Middleware { public static function handle($request, Closure $closure); } class CheckForMaintenanceMode implements Middleware { public static function handle($request, Closure $next) { echo $request . ': Check if the application is in the maintenance status.' . PHP_EOL; $next($request); } } class AddQueuedCookiesToResponse implements Middleware { public static function handle($request, Closure $next) { $next($request); echo $request . ': Add queued cookies to the response.' . PHP_EOL; } } class StartSession implements Middleware { public static function handle($request, Closure $next) { echo $request . ': Start session of this request.' . PHP_EOL; $next($request); echo $request . ': Close session of this response.' . PHP_EOL; } } class ShareErrorsFromSession implements Middleware { public static function handle($request, Closure $next) { $next($request); echo $request . ': Share the errors variable from response to the views.' . PHP_EOL; } } class VerifyCsrfToken implements Middleware { public static function handle($request, Closure $next) { echo $request . ': Verify csrf token when post request.' . PHP_EOL; $next($request); } }給上完整的一個Pipeline類，這里的Pipeline對Laravel中的Pipeline做了稍微簡化，只選了幾個重要的函數(shù)：
// PipelineTest.php class Pipeline { /** * @var array */ protected $middlewares = []; /** * @var int */ protected $request; // Get the initial slice function getInitialSlice(Closure $destination) { return function ($passable) use ($destination) { return call_user_func($destination, $passable); }; } // Get the slice in every step. function getSlice() { return function ($stack, $pipe) { return function ($passable) use ($stack, $pipe) { /** * @var Middleware $pipe */ return call_user_func_array([$pipe, 'handle'], [$passable, $stack]); }; }; } // When process the Closure, send it as parameters. Here, input an int number. function send(int $request) { $this->request = $request; return $this; } // Get the middlewares array. function through(array $middlewares) { $this->middlewares = $middlewares; return $this; } // Run the Filters. function then(Closure $destination) { $firstSlice = $this->getInitialSlice($destination); $pipes = array_reverse($this->middlewares); $run = array_reduce($pipes, $this->getSlice(), $firstSlice); return call_user_func($run, $this->request); } }OK,現(xiàn)在開始傳入Request,這里簡化為一個整數(shù)而不是Request對象了：
// PipelineTest.php /** * @return \Closure */ function dispatchToRouter() { return function ($request) { echo $request . ': Send Request to the Kernel, and Return Response.' . PHP_EOL; }; } $request = 10; $middlewares = [ CheckForMaintenanceMode::class, AddQueuedCookiesToResponse::class, StartSession::class, ShareErrorsFromSession::class, VerifyCsrfToken::class, ]; (new Pipeline())->send($request)->through($middlewares)->then(dispatchToRouter());執(zhí)行php PipelineTest.php得到Response：
10: Check if the application is in the maintenance status. 10: Start session of this request. 10: Verify csrf token when post request. 10: Send Request to the Kernel, and Return Response. 10: Share the errors variable from response to the views. 10: Close session of this response. 10: Add queued cookies to the response.
一步一步分析下執(zhí)行過程：
1.首先獲取$firstSlice
$destination = function ($request) { echo $request . ': Send Request to the Kernel, and Return Response.' . PHP_EOL; }; $firstSlice = function ($passable) use ($destination) { return call_user_func($destination, $passable); };這時經(jīng)過初始化后：
$this->request = 10; $pipes = [ VerifyCsrfToken::class, ShareErrorsFromSession::class, StartSession::class, AddQueuedCookiesToResponse::class, CheckForMaintenanceMode::class, ];
2.執(zhí)行***次getSlice()后的結(jié)果作為新的$stack，其值為：
$stack = $firstSlice; $pipe = VerifyCsrfToken::class; $stack_1 = function ($passable) use ($stack, $pipe) { /** * @var Middleware $pipe */ return call_user_func_array([$pipe, 'handle'], [$passable, $stack]); };3.執(zhí)行第二次getSlice()后的結(jié)果作為新的$stack，其值為：
$stack = $stack_1; $pipe = ShareErrorsFromSession::class; $stack_2 = function ($passable) use ($stack, $pipe) { /** * @var Middleware $pipe */ return call_user_func_array([$pipe, 'handle'], [$passable, $stack]); };4.執(zhí)行第三次getSlice()后的結(jié)果作為新的$stack，其值為：
$stack = $stack_2; $pipe = StartSession::class; $stack_3 = function ($passable) use ($stack, $pipe) { /** * @var Middleware $pipe */ return call_user_func_array([$pipe, 'handle'], [$passable, $stack]); };5.執(zhí)行第四次getSlice()后的結(jié)果作為新的$stack，其值為：
$stack = $stack_3; $pipe = AddQueuedCookiesToResponse::class; $stack_4 = function ($passable) use ($stack, $pipe) { /** * @var Middleware $pipe */ return call_user_func_array([$pipe, 'handle'], [$passable, $stack]); };6.執(zhí)行第五次getSlice()后的結(jié)果作為新的$stack，其值為：
$stack = $stack_4; $pipe = CheckForMaintenanceMode::class; $stack_5 = function ($passable) use ($stack, $pipe) { /** * @var Middleware $pipe */ return call_user_func_array([$pipe, 'handle'], [$passable, $stack]); };這時，$stack_5也就是then()里的$run,然后執(zhí)行call_user_func($run, 10),看執(zhí)行過程:
1.$stack_5(10) = CheckForMaintenanceMode::handle(10, $stack_4)
echo '10: Check if the application is in the maintenance status.' . PHP_EOL; stack_4(10);
2.$stack_4(10) = AddQueuedCookiesToResponse::handle(10, $stack_3)
$stack_3(10); echo '10: Add queued cookies to the response.' . PHP_EOL;
3.$stack_3(10) = StartSession::handle(10, $stack_2)
echo '10: Start session of this request.' . PHP_EOL; $stack_2(10); echo '10: Close session of this response.' . PHP_EOL;
4.$stack_2(10) = ShareErrorsFromSession::handle(10, $stack_1)
$stack_1(10); echo '10: Share the errors variable from response to the views.' . PHP_EOL;
5.$stack_1(10) = VerifyCsrfToken::handle(10, $firstSlice)
echo '10: Verify csrf token when post request.' . PHP_EOL; $firstSlice(10);
6.$firstSlice(10) =
$firstSlice(10) = call_user_func($destination, 10) = echo '10: Send Request to the Kernel, and Return Response.' . PHP_EOL;
OK,再把上面執(zhí)行順序整理一下：
1. echo '10: Check if the application is in the maintenance status.' . PHP_EOL; // ***個step 3_1. echo '10: Start session of this request.' . PHP_EOL; // 第三個step 5. echo '10: Verify csrf token when post request.' . PHP_EOL; // 第五個step 6.echo '10: Send Request to the Kernel, and Return Response.' . PHP_EOL; //第六個step 4. echo '10: Share the errors variable from response to the views.' . PHP_EOL; // 第四個step 3_2. echo '10: Close session of this response.' . PHP_EOL; // 第三個step 2. echo '10: Add queued cookies to the response.' . PHP_EOL; // 第二個step
看完上述內(nèi)容，你們對Laravel中Middleware如何使用有進一步的了解嗎？如果還想了解更多知識或者相關(guān)內(nèi)容，請關(guān)注創(chuàng)新互聯(lián)行業(yè)資訊頻道，感謝大家的支持。
標(biāo)題名稱：Laravel中Middleware如何使用
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