GAE + Java – Integrating Google user account

By mkyong | Updated: August 29, 2012

Viewed: 17,110

Tags: gae java

For this tutorial, we will show you how to integrate Google user account in GAE + Java project, via Google Java SDK UserService class.

Tools used :

1. JDK 1.6
2. Eclipse 3.7 + Google Plugin for Eclipse
3. Google App Engine Java SDK 1.6.3.1

1. GAE User service example

If user login by using their Google account, display a welcome message and a “Logout” link; Otherwise display a “Login” link.

package com.mkyong.user;

import java.io.IOException;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.appengine.api.users.User;
import com.google.appengine.api.users.UserService;
import com.google.appengine.api.users.UserServiceFactory;

@SuppressWarnings("serial")
public class LoginExampleServlet extends HttpServlet {
	public void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws IOException {

		UserService userService = UserServiceFactory.getUserService();
		User user = userService.getCurrentUser();

		resp.setContentType("text/html");
		resp.getWriter().println("<h2>GAE - Integrating Google user account</h2>");
		
		if (user != null) {
			
			resp.getWriter().println("Welcome, " + user.getNickname());
			resp.getWriter().println(
				"<a href='"
					+ userService.createLogoutURL(req.getRequestURI())
					+ "'> LogOut </a>");

		} else {

			resp.getWriter().println(
				"Please <a href='"
					+ userService.createLoginURL(req.getRequestURI())
					+ "'> LogIn </a>");

		}
	}
}

2. Run it locally

Right click on the project and run as “Web Application”. By default, it run at post 8888.

Figure 2.1 : Access URL : http://localhost:8888/loginexample

Figure 2.2 : A simulated Google’s login screen, type something, no authentication.

Figure 2.3 : welcome, and display a logout link.

3. Deploy on GAE

Deploy Google App Engine, using application ID, “mkyong-java“.

Figure 3.1 – Access URL : http://mkyong-java.appspot.com/loginexample

Figure 3.2 – Redirect to actual Google account login screen.

Figure 3.3 – If Login is successful, redirect back to http://mkyong-java.appspot.com/loginexample

Download Source Code

Due to large file size, all GAE SDK dependency libraries are excluded.

References

1. Using the Users Service
2. The Users Java API
3. GAE UserService JavaDoc
4. GAE Java hello world example