index.php

//Index.php
<html>
    <head>
        <title>Acceso al Sistema</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
            <!-- Bootstrap core CSS -->
                <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">

        <!-- Custom styles for this template -->
            <link REL=styleSheet HREF="css/style.css" TYPE="text/css" MEDIA=screen>

        <link href="css/login2.css" rel="stylesheet" TYPE="text/css" MEDIA=screen>
    </head>
    <body>
        <div class="container">
            <div class="d-flex justify-content-md-center h-50">
                <div class= "card">
                    <form class="form-signin" action="controller/ControllerValidarAcceso.php" method="post">
                      <input type="hidden" name="${_csrf.parameterName}" value="${_csrf.token}"/>
                        <h2 class="form-signin-heading">TuLimaPass</h2>
                        <div> Usuario:
                        <label for="inputEmail" class="sr-only">Username</label>
                        <input type="text" class="form-control" placeholder="Username" name="username" id="username"/>
                        </div>
                        <div> Contraseña:
                        <label for="inputPassword" class="sr-only">Password</label>
                        <input type="password" class="form-control" placeholder="Password" name="password" id="password"/>
                        </div>
                        <button class="btn btn-lg btn-primary btn-block" type="submit" name="signin">
                            <span class="glyphicon glyphicon-log-in" aria-hidden="true"></span> Ingresar
                        </button>
                        <h6 class="form-signin-heading"><a href="view/registro.php">Registrese...</a></h6>
                    </form>
                </div>
            </div>
        </div> <!-- /container -->
    </body>
</html>