Q:

How to force FormRequest return json in Laravel 5.1?

I'm using  FormRequest to validate from which is sent in an API call from my smartphone app. So, I want FormRequest alway return json when validation fail.
I saw the following source code of Laravel framework, the default behaviour of FormRequest is return json if reqeust is Ajax or wantJson.
//Illuminate\Foundation\Http\FormRequest class
/**
 * Get the proper failed validation response for the request.
 *
 * @param  array  $errors
 * @return \Symfony\Component\HttpFoundation\Response
 */
public function response(array $errors)
{
    if ($this->ajax() || $this->wantsJson()) {
        return new JsonResponse($errors, 422);
    }

    return $this->redirector->to($this->getRedirectUrl())
                                    ->withInput($this->except($this->dontFlash))
                                    ->withErrors($errors, $this->errorBag);
}

I knew that I can add Accept= application/json in request header. FormRequest will return json. But I want to provide an easier way to request my API by support json in default without setting any header. So, I tried to find some options to force FormRequest response json in Illuminate\Foundation\Http\FormRequest class. But I didn't find any options which are supported in default. 
Solution 1 : Overwrite Request Abstract Class
I tried to overwrite my application request abstract class like followings:
<?php

namespace Laravel5Cg\Http\Requests;

use Illuminate\Foundation\Http\FormRequest;
use Illuminate\Http\JsonResponse;

abstract class Request extends FormRequest
{
    /**
     * Force response json type when validation fails
     * @var bool
     */
    protected $forceJsonResponse = false;

    /**
     * Get the proper failed validation response for the request.
     *
     * @param  array  $errors
     * @return \Symfony\Component\HttpFoundation\Response
     */
    public function response(array $errors)
    {
        if ($this->forceJsonResponse || $this->ajax() || $this->wantsJson()) {
            return new JsonResponse($errors, 422);
        }

        return $this->redirector->to($this->getRedirectUrl())
            ->withInput($this->except($this->dontFlash))
            ->withErrors($errors, $this->errorBag);
    }
}

I added protected $forceJsonResponse = false; to setting if we need to force response json or not. And, in each FormRequest which is extends from Request abstract class. I set that option. 
Eg:  I made an StoreBlogPostRequest and set $forceJsoResponse=true for this FormRequest and make it response json.
<?php

namespace Laravel5Cg\Http\Requests;

use Laravel5Cg\Http\Requests\Request;

class StoreBlogPostRequest extends Request
{

    /**
     * Force response json type when validation fails
     * @var bool
     */

     protected $forceJsonResponse = true;
    /**
     * Determine if the user is authorized to make this request.
     *
     * @return bool
     */
    public function authorize()
    {
        return true;
    }

    /**
     * Get the validation rules that apply to the request.
     *
     * @return array
     */
    public function rules()
    {
        return [
            'title' => 'required|unique:posts|max:255',
            'body' => 'required',
        ];
    }
}

Solution 2: Add an Middleware and force change request header
I build a middleware like followings:
    

namespace Laravel5Cg\Http\Middleware;

use Closure;
use Symfony\Component\HttpFoundation\HeaderBag;

class AddJsonAcceptHeader
{
    /**
     * Add Json HTTP_ACCEPT header for an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        $request->server->set('HTTP_ACCEPT', 'application/json');
        $request->headers = new HeaderBag($request->server->getHeaders());
        return $next($request);
    }
}

It 's work. But I wonder is this solutions good? And are there any Laravel Way to help me in this situation ? 

A:

It boggles my mind why this is so hard to do in Laravel. In the end, based on your idea to override the Request class, I came up with this.
app/Http/Requests/ApiRequest.php
<?php

namespace App\Http\Requests;

class ApiRequest extends Request
{
    public function wantsJson()
    {
        return true;
    }
}

Then, in every controller just pass \App\Http\Requests\ApiRequest
public function index(ApiRequest $request)

A:

I know this post is kind of old but I just made a Middleware that replaces the "Accept" header of the request with "application/json". This makes the wantsJson() function return true when used. (This was tested in Laravel 5.2 but I think it works the same in 5.1)
Here's how you implement that :

Create the file app/Http/Middleware/Jsonify.php
namespace App\Http\Middleware;

use Closure;

class Jsonify
{

    /**
     * Change the Request headers to accept "application/json" first
     * in order to make the wantsJson() function return true
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * 
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        $request->headers->set('Accept', 'application/json');

        return $next($request);
    }
}

Add the middleware to your $routeMiddleware table of your app/Http/Kernel.php file
protected $routeMiddleware = [
    'auth'       => \App\Http\Middleware\Authenticate::class,
    'guest'      => \App\Http\Middleware\RedirectIfAuthenticated::class,
    'jsonify'    => \App\Http\Middleware\Jsonify::class
];

Finally use it in your routes.php as you would with any middleware. In my case it looks like this :
Route::group(['prefix' => 'api/v1', 'middleware' => ['jsonify']], function() {
    // Routes
});

