Laravel验证如何在没有try catch的情况下将Exception作为Json返回？

I'm bulding an exception log into my Laravel app to send mails or Telegram messages when an error identified as important is dispatched. Actually, I'm using a 'try catch' block on each of my controller functions to catch an exception dispathced by any part of my app. My question is, how does Laravel validation works to return exceptions as JSON response without using return sentences or try catch blocks on each call?

What I must do now into controller:

someAction();

try {
    Model::someFunction($params);
catch (MyCustomException $e)
    return json()->response($e->getMessage(), 500); // Return json error if fails
}

return anotherAction();

What I want to do into controller:

someAction();

Model::someFunction($params); // Return json error if fails and stop execution

return anotherAction();

What Laravel validation makes:

someAction();

$request->validate($validationRules); // Return json error if validation fails and stop execution

return anotherAction();

You can make a validator

<?php

use Validator;
use Illuminate\Http\Request;

class MyController extends Controller {

    public function myFunction(Request $request)
    {
        $validator = Validator::make($request->all(), [
            'foo' => 'required',
            'bar' => 'required'
        ]);

        if ($validator->passes()) {

        }

        if ($validator->fails()) {

        }
    }
}