@@ -0,0 +1,2121 @@
+// Copyright 2019 Google LLC%0A//%0A// Licensed under the Apache License, Version 2.0 (the %22License%22);%0A// you may not use this file except in compliance with the License.%0A// You may obtain a copy of the License at%0A//%0A//     https://www.apache.org/licenses/LICENSE-2.0%0A//%0A// Unless required by applicable law or agreed to in writing, software%0A// distributed under the License is distributed on an %22AS IS%22 BASIS,%0A// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.%0A// See the License for the specific language governing permissions and%0A// limitations under the License.%0A%0Apackage com.google.sps.servlets;%0A%0Aimport com.google.appengine.api.datastore.*;%0Aimport com.google.appengine.api.users.UserService;%0Aimport com.google.appengine.api.users.UserServiceFactory;%0Aimport com.google.gson.Gson;%0Aimport com.google.gson.JsonObject;%0Aimport java.io.IOException;%0Aimport java.io.PrintWriter;%0Aimport javax.servlet.annotation.WebServlet;%0Aimport javax.servlet.http.HttpServlet;%0Aimport javax.servlet.http.HttpServletRequest;%0Aimport javax.servlet.http.HttpServletResponse;%0A%0A@WebServlet(%22/login-link%22)%0Apublic class LoginServlet extends HttpServlet %7B%0A%0A    // Request: param %22redirectUrl%22 for after login is finished (defaults to index.html).%0A    // Response: param %22isUserLoggedIn%22 : boolean, %22loginPageUrl%22 : String. %0A    @Override%0A    public void doGet (HttpServletRequest request, HttpServletResponse response) throws IOException %7B%0A        response.setContentType(%22application/json%22);%0A        UserService userService = UserServiceFactory.getUserService();%0A%0A        String redirectUrl = request.getAttribute(%22redirectUrl%22);%0A        if (redirectUrl == null) %7B%0A            redirectUrl = %22/%22;%0A        %7D%0A%0A        JsonObject json = new JsonObject();%0A%0A        if (!userService.isUserLoggedIn()) %7B%0A            String loginPageUrl = userService.createLoginURL(redirectUrl);%0A            json.addProperty(%22loginPageUrl%22, loginUrl);%0A            json.addProperty(%22isUserLoggedIn%22, false);%0A        %7D else %7B%0A            json.addProperty(%22isUserLoggedIn%22, true);%0A        %7D%0A%0A        response.getWriter().println(json.toString());%0A    %7D%0A%7D

add servlet directory and login servlet starter code