Ciao a tutti,

Ho un problema riguardante richieste http da inviare in remoto, la quale una volta eseguita mi restituisce 0. Ho letto che il problema potrebbe essere risolto tramite JSONP o CORS, anche se ho trovato poco a riguardo online per il mio utilizzo. Qualcuno li conosce e può aiutarmi?

Ecco il codice
codice HTML:
<!doctype html>
<html lang="it">
  <head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <link href="css/style.css" rel="stylesheet">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
    <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.0/jquery.min.js"></script>

    <title>Login</title>

    <script>
        $(document).ready(function(){
            $("#lsubmit").click(function(){
                var username = $("#lmail").val();
                var password = $("#lpsw").val();
                //var auth = username + ':' + password;

                $.ajax({
                    url : 'http://localhost:8080/sellers/users/0',
                    method : 'POST',
                    data: '{"username": "' + username + '", "password" : "' + password + '"}',
                    dataType: 'json',
                    crossDomain: true,
                    beforeSend : function(req) {
                        req.setRequestHeader('Authorization', "Basic " + btoa(username+":"+ password));
                    },
                    success: function(){
                        alert('success!');
                    },
                    error: function (request, status, error) {
                        alert(request.status);
                    }
                });
            });
        });
    </script>
  </head>
  <body>

    <div class="container text-center">

      <img src="img/shoppy.png" class="img-fluid logo2" alt="Responsive image">
      <h1 class="tit">Benvenuto, accedi al tuo portale.</h1><br>

      <div class="row justify-content-center">

        <form class="login">

          <!--<input type="text" id="partita_iva" class="form-control" placeholder="Partita Iva" size="30" required 
          pattern="[0-9]{11}" autofocus>

          <input type="number" id="partita_iva" class="form-control" placeholder="Partita Iva" size="30" required 
          min="11" max="11" autofocus>-->

          <input type="text" class="form-control" id="lmail" name="lmail" placeholder="Indirizzo Email" required>


          <input type="password" id="lpsw" class="form-control" placeholder="Password" size="40" required><br>

          <button class="btn-primary btn-lg btn-block text-uppercase" type="submit" size="40" id="lsubmit">Accedi</button>

        </form>

      </div><br>

      <p >Non ti sei ancora iscritto? <a href="iscrizione.html">Fallo subito</a></p>
      <p class="minusc">Se hai dimenticato la password contattaci con la tua email di registrazione al nostro indirizzo: shoppy@gmail.com</p>

    </div>



    <!-- Optional JavaScript, jQuery first, then Popper.js, then Bootstrap JS
    <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
    -->
    </div>
  </body>
</html>