opt-cc/static/src/app/login/login.component.html

<form class="form-signin" (ngSubmit)="login(userName.value, password.value)">
  <div class="row">
    <h2 class="form-signin-heading">Login</h2>

    <label for="inputEmail" class="sr-only">Benutzername</label>
    <input #userName id="inputEmail" class="form-control" placeholder="Benutzername" required="" autofocus="">

    <label for="inputPassword" class="sr-only">Passwort</label>
    <input #password type="password" id="inputPassword" class="form-control" placeholder="Passwort" required="">

    <div class="form-group">
      <button mat-stroked-button type="submit">
        <span *ngIf="!loading">Anmelden</span>
        <span *ngIf="loading" class="glyphicon glyphicon-refresh glyphicon-refresh-animate"></span>
      </button>
    </div>
  </div>
</form>