场景

• lumen5.5环境在定义了一个跨域的中间件,在使用 maatwebsite/excel download方法的时候，报错
  :Call to undefined method Symfony\Component\HttpFoundation\BinaryFileResponse::header()

参考文档

• maatwebsite/excel

原来的中间件

    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request $request
     * @param  \Closure $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {


        return $next($request)->header('Access-Control-Allow-Origin', '*')
            ->header('Access-Control-Allow-Methods', 'GET,POST,PUT,OPTIONS,PATCH,DELETE,HEAD')
            ->header('Access-Control-Allow-Headers', 'x-csrf-token,x-requested-with,content-type');
    }

分析

• 一般情况下 $next($request) 返回的是 Illuminate\Http\Response, 但是使用Excel::download的时候
  是\Symfony\Component\HttpFoundation\Response的实例；

解决

    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request $request
     * @param  \Closure $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        $response = $next($request);

        if ($response instanceof  Response) {
            return $next($request)->header('Access-Control-Allow-Origin', '*')
                ->header('Access-Control-Allow-Methods', 'GET,POST,PUT,OPTIONS,PATCH,DELETE,HEAD')
                ->header('Access-Control-Allow-Headers', 'x-csrf-token,x-requested-with,content-type');
        }

        //  如果是实列 \Symfony\Component\HttpFoundation\Response::class
        $response->headers->set('Access-Control-Allow-Origin', '*');
        $response->headers->set('Access-Control-Allow-Methods', 'GET,POST,PUT,OPTIONS,PATCH,DELETE,HEAD');
        $response->headers->set('Access-Control-Allow-Headers', 'x-csrf-token,x-requested-with,content-type');
        return $response;
    }