gistfile1.pde

@Singleton
public class AuthFilter<R extends Request> extends BaseFilter<R> {
  private final String loginUrl;

  @Inject
  public AuthFilter(@Named("loginUrl") String loginUrl) {
    this.loginUrl = loginUrl;
  }

  @Override
  public Response before(R request, Class<? extends Handler<R>> handlerClass) {
    if (handlerClass.getAnnotation(RequiresLogin.class) != null && !request.isLoggedIn()) {
      return new RedirectResponse(loginUrl + "?target=" + request.getReconstructedUrl());
    } else {
      return null;
    }
  }
}