#{form @Application.auth(), id:'loginForm'}
    <p>
        <label>LOGIN:</label>
        <input type="text" id="login" name="login" value="${flash.login}" />
    </p>
    <p>
        <label>PASSWORD:</label>
        <input type="password" id="pass" name="pass" value="" />
    </p>
    <p class="action">
        <input type="submit" value="Go!" onclick="valid()">
    </p>
#{/form}
<p>
    <a href="@{registration()}">Зарегестрироваться</a>

public static void auth(String username, String password) {
        User user = User.findByUsername(username);
        if (username == null || !user.checkPass(password)) {
            flash.error("Bad username or password");
        }
        session.put("username", username);
        if (user != null) {
            flash.success("Welcome %s !", username);
            profileUser();
        }
    }

File routes:
# Home page
GET     /                                   controllers.Application.index()
POST    /login                              controllers.Application.auth()