Authenticates user and saves username to session, otherwise shows login form with errors.

Controller.java

		String username = form.get("username")[0];
		String password = form.get("password")[0];
		
		boolean usernameIsEmpty = "".equals(username);
		boolean passwordIsEmpty = "".equals(password);
		
		if(usernameIsEmpty || passwordIsEmpty){
			if(usernameIsEmpty){
				flash().put("username-empty", "yes");
			}
			if(passwordIsEmpty){
				flash().put("password-empty", "yes");
			}
			
			return redirect(routes.AuthenticationController.showLoginForm());
		}
		
		TypedQuery<User> query = JPA.em().createQuery( "SELECT c FROM User c WHERE c.username = :username AND c.password = :password", User.class);
		query.setParameter("username", username);
		query.setParameter("password", password);
		
		List<User> matchingUsers = query.getResultList();
		
		if(matchingUsers.size() == 1){
			session().put("username", username);
			
			return redirect(routes.DefaultController.index());
		} else {
			flash().put("no-username-password-match", "yes");
			
			return redirect(routes.AuthenticationController.showLoginForm());
		}

login.scala.html

@if(flash.containsKey("username-empty")){
	<div class="alert alert-warning">Username required.</div>
}

@if(flash.containsKey("password-empty")){
	<div class="alert alert-warning">Password required.</div>
}

@if(flash.containsKey("no-username-password-match")){
	<div class="alert alert-warning">No username exists with this password.</div>
}

<form role="form" action="@routes.AuthenticationController.login" method="post">
  <div class="form-group">
    <label for="username">Username</label>
    <input type="text" class="form-control" id="username" name="username">
  </div>
  <div class="form-group">
    <label for="password">Password</label>
    <input type="text" class="form-control" id="password" name="password">
  </div>
  <button type="submit" class="btn btn-default">Submit</button>
</form>