An in-depth analysis of controllers in the Laravel framework

protected $middleware = [
    \Illuminate\Foundation\Http\Middleware\CheckForMaintenanceMode::class,
    \Illuminate\Foundation\Http\Middleware\ValidatePostSize::class,
    \App\Http\Middleware\TrimStrings::class,
    \Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,
    \App\Http\Middleware\TrustProxies::class,
];

namespace Illuminate\Foundation\Http;
class Kernel implements KernelContract
{
    protected function dispatchToRouter()
    {
        return function ($request) {
            $this->app->instance('request', $request);

            return $this->router->dispatch($request);
        };
    }
}


namespace Illuminate\Routing;
class Router implements RegistrarContract, BindingRegistrar
{    
    public function dispatch(Request $request)
    {
        $this->currentRequest = $request;

        return $this->dispatchToRoute($request);
    }
    
    public function dispatchToRoute(Request $request)
    {
        return $this->runRoute($request, $this->findRoute($request));
    }
    
    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()
                        );
                    });
    
    }
}

namespace Illuminate\Routing;
class Route
{
    public function run()
    {
        $this->container = $this->container ?: new Container;
        try {
            if ($this->isControllerAction()) {
                return $this->runController();
            }
            return $this->runCallable();
        } catch (HttpResponseException $e) {
            return $e->getResponse();
        }
    }

}

[
    'uses' => 'App\Http\Controllers\SomeController@someAction',
    'controller' => 'App\Http\Controllers\SomeController@someAction',
    'middleware' => ...
]

class Route
{
    protected function isControllerAction()
    {
        return is_string($this->action['uses']);
    }

    protected function runController()
    {
        return (new ControllerDispatcher($this->container))->dispatch(
            $this, $this->getController(), $this->getControllerMethod()
        );
    }
    
    public function getController()
    {
        if (! $this->controller) {
            $class = $this->parseControllerCallback()[0];

            $this->controller = $this->container->make(ltrim($class, '\\'));
        }

        return $this->controller;
    }
    
    protected function getControllerMethod()
    {
        return $this->parseControllerCallback()[1];
    }
    
    protected function parseControllerCallback()
    {
        return Str::parseCallback($this->action['uses']);
    }
}

class Str
{
    //解析路由里绑定的控制器方法字符串，返回控制器和方法名称字符串构成的数组
    public static function parseCallback($callback, $default = null)
    {
        return static::contains($callback, '@') ? explode('@', $callback, 2) : [$callback, $default];
    }
}

class ControllerDispatcher
{
    use RouteDependencyResolverTrait;

    public function dispatch(Route $route, $controller, $method)
    {
        $parameters = $this->resolveClassMethodDependencies(
            $route->parametersWithoutNulls(), $controller, $method
        );

        if (method_exists($controller, 'callAction')) {
            return $controller->callAction($method, $parameters);
        }

        return $controller->{$method}(...array_values($parameters));
    }
}

trait RouteDependencyResolverTrait
{
    protected function resolveClassMethodDependencies(array $parameters, $instance, $method)
    {
        if (! method_exists($instance, $method)) {
            return $parameters;
        }
        
        
        return $this->resolveMethodDependencies(
            $parameters, new ReflectionMethod($instance, $method)
        );
    }

    //参数为路由参数数组$parameters(可为空array)和控制器方法的反射对象
    public function resolveMethodDependencies(array $parameters, ReflectionFunctionAbstract $reflector)
    {
        $instanceCount = 0;

        $values = array_values($parameters);

        foreach ($reflector->getParameters() as $key => $parameter) {
            $instance = $this->transformDependency(
                $parameter, $parameters
            );

            if (! is_null($instance)) {
                $instanceCount++;

                $this->spliceIntoParameters($parameters, $key, $instance);
            } elseif (! isset($values[$key - $instanceCount]) &&
                      $parameter->isDefaultValueAvailable()) {
                $this->spliceIntoParameters($parameters, $key, $parameter->getDefaultValue());
            }
        }

        return $parameters;
    }
    
}

    protected function transformDependency(ReflectionParameter $parameter, $parameters)
    {
        $class = $parameter->getClass();
        if ($class && ! $this->alreadyInParameters($class->name, $parameters)) {
            return $parameter->isDefaultValueAvailable()
                ? $parameter->getDefaultValue()
                : $this->container->make($class->name);
        }
    }
    
    protected function alreadyInParameters($class, array $parameters)
    {
        return ! is_null(Arr::first($parameters, function ($value) use ($class) {
            return $value instanceof $class;
        }));
    }

    protected function spliceIntoParameters(array &$parameters, $offset, $value)
    {
        array_splice(
            $parameters, $offset, 0, [$value]
        );
    }

} elseif (! isset($values[$key - $instanceCount]) &&
    $parameter->isDefaultValueAvailable()) {
    $this->spliceIntoParameters($parameters, $key, $parameter->getDefaultValue());
}

    public function dispatch(Route $route, $controller, $method)
    {
        $parameters = $this->resolveClassMethodDependencies(
            $route->parametersWithoutNulls(), $controller, $method
        );

        if (method_exists($controller, 'callAction')) {
            return $controller->callAction($method, $parameters);
        }

        return $controller->{$method}(...array_values($parameters));
    }