How to output just raw json from my Joomla controller for Ajax requests?

Question

I want to create a Joomla json response for an Ajax request. So, I followed the instructions here: JSON Responses with JResponseJson

I implement the following code in my controller:

use \Joomla\CMS\Response\JsonResponse;

class RamControllerAjax extends JControllerLegacy
{
    public function capitals()
    {
        try
        {
            $country = JFactory::getApplication()->input->get('country');

            if      ($country == 'UK')      $capital = 'London';
            elseif  ($country == 'Spain')   $capital = 'Madrid';
            else                            $capital = "I don't know";

            $capital_json = json_encode($capital);
            echo new JsonResponse($capital_json);
        }
        catch(Exception $e)
        {
            echo new JsonResponse($e);
        }
    }
}

When I call it with the URL: http://joomla_clasificados/index.php?option=com_ram&task=ajax.capitals&country=UK

I receive the correct json response:

{"success":true,"message":null,"messages":null,"data":"\"London\""}

But inserted in the middle of a normal Joomla page. Like this:

What I want is the json response alone. I tried some changes in the URL, like:

http://joomla_clasificados/index.php?option=com_ram&task=ajax.capitals&country=UK&format=json

that gives me the error:

Invalid controller: name='ajax', format='json'

Same thing with format=raw variant.

What I am doing wrong ? How could I get only the json response?

Answer 1

To use format=json query parameter, the controller filename needs to be suffixed with the format, e.g. ajax.json.php. This is mentioned in the linked documentation:

If you are developing an MVC component, save such a controller in a file called mycontroller.json.php and place it inside your controllers folder. That controller is automatically executed if your request URL contains format=json.