Validation parameter of get request laravel

Route::get("/subject/{subject_id}", "SubjectInfo");

//controller

use Illuminate\Support\Facades\Validator;

  public function SubjectInfo(Request $request)

    {

        try {

            $validator = Validator::make($request->route()->parameters(), [

                'subject_id' => 'required|exists:subjects,id'

            ]);

            if ($validator->fails()) {

                return ResponseBuilder::error($validator->errors()->first(), $this->errorStatus);

            }

            $subject = Subject::find($request->subject_id);

            $this->response = new SubjectResource($subject);

            return ResponseBuilder::success($this->response);

        } catch (\Exception $e) {

            Log::error($e);

        }

    }