Login with Google using Java - Tutorial

Friday 21 November 2014 | Posted by Sample

Google is providing OAuth Service. You can implement Google Login on your website so that user doesn't need to remember another password for your website. You will also get worthy email addresses to connect with users. Get Google GSON Java Library to handle JSON responses.

OAuth 2.0 Flow

User will click on Auth login link
Google Auth server will show permission screen to user
Once user accepts to the scope, It will send code to App Server ( Redirect URI)
Once we got code, get access token by using client secret id
Access User's Information using that access token

Get OAuth 2.0 Credentials from Google developer console

Go to Google Developer Console
Create Project and Open that project
Go to API & Auth > Credentials > Create New Client ID. Here one new dialog box will open and show some options. Now select web application, Give you website URL (example: http://demo.sodhanalibrary.com) in JavaScript origins and Give redirect URL (example: http://demo.sodhanalibrary.com/oauth2callback). Now click on Create Client ID button.
Now you can see your client id and client secret id.

Demo - Login with Google using Java

Sample Project

Click here to download the eclipse project. Open Setup.java and enter app details, Open index.html and format login URL with your own app details

Form the URL

Now we need to create a button with Auth URL. Syntax of the URL is

https://accounts.google.com/o/oauth2/auth?[parameters]

Some important Query Paramenters

client_id: Which you got at Google developer console
response_id: For web application response_id is code
redirect_uri: Redirect URI which you given at Google developer console
scope: to get profile info give profile as scope, to get email address give email as scope
approval_prompt: (force or auto) If it is force, user must accept to your scope or else it will be optional.

The Auth URL get Users Email Address

https://accounts.google.com/o/oauth2/auth?

scope=email&

redirect_uri=http://demo.sodhanalibrary.com/oauth2callback&

response_type=code&

client_id=your application client id&

approval_prompt=force

Get Access Token

Once user click on above link, It will ask for User's permission to provide information to your site. Once user click on accept it will redirect to Your APP Redirect URI?code=[some code here]. Here you will get code value at server side. So you need to access this from Java or PHP or any other server side language.

Get Code Value and format Parameters

String code = request.getParameter("code");
String urlParameters = "code="
                    + code
                    + "&client_id=Your app client id"
                    + "&client_secret=Your app secret id"
                    + "&redirect_uri=http://demo.sodhanalibrary.com/oauth2callback"
                    + "&grant_type=authorization_code";

Now we have to send that code with client id and secret id to https://accounts.google.com/o/oauth2/token

Java code to post parameters

URL url = new URL("https://accounts.google.com/o/oauth2/token");
URLConnection urlConn = url.openConnection();
urlConn.setDoOutput(true);
OutputStreamWriter writer = new OutputStreamWriter(
urlConn.getOutputStream());
writer.write(urlParameters);
writer.flush();

Extract Access Token

After posting above parameters to Google Auth URL, we will get response which contains Access Token. Now extract that access token from that response.

JsonObject json = (JsonObject)new JsonParser().parse(line1);
String access_token = json.get("access_token").getAsString();

Get User Info

Now we have access token so we can get user info.

url = new URL("https://www.googleapis.com/oauth2/v1/userinfo?access_token="+ access_token);
urlConn = url.openConnection();
outputString = "";
reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
while ((line = reader.readLine()) != null) {
        outputString += line;
}

In the above code outputString contains the User Info

User info in JSON format

  {
    "id":"user id here",
    "email":"email here",
    "name":"name here",
    "given_name":"given name here", 
    "family_name":"family name here"  
  }

POJO Class to handle JSON rensponse

public class GooglePojo {
    String id;
    String email;
    boolean verified_email;
    String name;
    String given_name;
    String family_name;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public boolean isVerified_email() {
        return verified_email;
    }

    public void setVerified_email(boolean verified_email) {
        this.verified_email = verified_email;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGiven_name() {
        return given_name;
    }

    public void setGiven_name(String given_name) {
        this.given_name = given_name;
    }

    public String getFamily_name() {
        return family_name;
    }

    public void setFamily_name(String family_name) {
        this.family_name = family_name;
    }

    @Override
    public String toString() {
        return "GooglePojo [id=" + id + ", email=" + email
                + ", verified_email=" + verified_email + ", name=" + name
                + ", given_name=" + given_name + ", family_name=" + family_name
                + "]";
    }
}

Whole Servlet Code

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;
import java.net.URLConnection;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.google.gson.Gson;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

public class Oauth2callback extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public Oauth2callback() {
        super();
        
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        
        System.out.println("entering doGet");
        try {
            // get code
            String code = request.getParameter("code");
            // format parameters to post
            String urlParameters = "code="
                    + code
                    + "&client_id=Your App Client ID"
                    + "&client_secret=Your App secret client ID"
                    + "&redirect_uri=Your App Redirect URL"
                    + "&grant_type=authorization_code";
            
            //post parameters
            URL url = new URL("https://accounts.google.com/o/oauth2/token");
            URLConnection urlConn = url.openConnection();
            urlConn.setDoOutput(true);
            OutputStreamWriter writer = new OutputStreamWriter(
                    urlConn.getOutputStream());
            writer.write(urlParameters);
            writer.flush();
            
            //get output in outputString 
            String line, outputString = "";
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    urlConn.getInputStream()));
            while ((line = reader.readLine()) != null) {
                outputString += line;
            }
            System.out.println(outputString);
            
            //get Access Token 
            JsonObject json = (JsonObject)new JsonParser().parse(outputString);
            String access_token = json.get("access_token").getAsString();
            System.out.println(access_token);

            //get User Info 
            url = new URL(
                    "https://www.googleapis.com/oauth2/v1/userinfo?access_token="
                            + access_token);
            urlConn = url.openConnection();
            outputString = "";
            reader = new BufferedReader(new InputStreamReader(
                    urlConn.getInputStream()));
            while ((line = reader.readLine()) != null) {
                outputString += line;
            }
            System.out.println(outputString);
            
            // Convert JSON response into Pojo class
            GooglePojo data = new Gson().fromJson(outputString, GooglePojo.class);
            System.out.println(data);
            writer.close();
            reader.close();
            
        } catch (MalformedURLException e) {
            System.out.println( e);
        } catch (ProtocolException e) {
            System.out.println( e);
        } catch (IOException e) {
            System.out.println( e);
        }
        System.out.println("leaving doGet");
    }

}

Labels:GOOGLE,JAVA

42 comments:

siddhu22 November 2014 at 22:59
is your server supports java?
ReplyDelete
Replies
Suram Sridhar3 May 2015 at 23:18
Can you please share the WAR file? It will be really help full to deploy and test?

Thanks
ReplyDelete
Replies
Anonymous29 June 2015 at 23:23
after getting access token i am unable to get the user info
ReplyDelete
Replies
Unknown5 September 2015 at 23:03
Hi Srini , I am not able to see the google page even after i hit the submit button. can you let me know what is the issue
ReplyDelete
Replies
Unknown16 November 2015 at 22:20
I am getting the same error. Please explain

entering doGet
java.io.IOException: Server returned HTTP response code: 400 for URL: https://accounts.google.com/o/oauth2/token
leaving doGet
ReplyDelete
Replies
Unknown21 May 2016 at 02:12
Hi,

please share your file, it will be helpful
ReplyDelete
Replies
Unknown28 May 2016 at 12:40
please share the project Srinivas.
ReplyDelete
Replies
Unknown13 June 2016 at 17:27
Hello Dasari, i registed my e-mail by http://downloads.sodhanalibrary.com/download?id=11, but i can't download it.
ReplyDelete
Replies
Unknown23 September 2016 at 06:32
Hi... Which Libraries are required ....????
ReplyDelete
Replies
Unknown11 November 2016 at 07:38
hi! if i have done my site whit tomcat, can i do this tutorial?
because in JavaScript origins and Give redirect URL i have localhost../nameProject and google don't accept this. please reply.
if i can't do this, how do i do?
ReplyDelete
Replies
Unknown30 November 2016 at 07:28
hi srinivas I had downloaded the war and trying to run from my local system and I had followed the above steps mentioned I able to get the code but while trying to get the access token I am facing the problem of (SSLHandShake Exception) is any thing more to be configured if needed kindly guide me and the error is occured at the line (OutputStreamWriter writer = new OutputStreamWriter(
conn.getOutputStream());
ReplyDelete
Replies
Unknown3 December 2016 at 02:52
Sir when my web page redirect then some error:

error is

HTTP Status 404 - /OAuth2Callback

type Status report

message /OAuth2Callback

description The requested resource is not available.
Apache Tomcat/8.0.36

my web page url is http://sumit.ap-south-1.elasticbeanstalk.com
ReplyDelete
Replies
Unknown7 December 2016 at 05:38
Hello Srinivas Dasari,

There is something wrong with download functionality : "http://downloads.sodhanalibrary.com/download?id=11".

I already have subscribed [24+:hr], but showing this : "Your email (*mail@mail.com) is not in our subscribed email list"

Tried to subscribe again, but now showing this : "*mail@mail.com is already subscribed to the mailing list of SodhanaLibrary".

Looks like deadlock.
ReplyDelete
Replies
Unknown21 December 2016 at 03:26
Hello Srinivas Dasari,
java.io.IOException: Server returned HTTP response code: 401 for URL: https://accounts.google.com/o/oauth2/token
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)

how to solve this error
ReplyDelete
Replies
Unknown22 December 2016 at 22:41
Hello Srinivas Dasari,
nothing wrong in client id and client_secret.I wrote redirect url like(http://localhost:8080/GoogleAuth/oauth2callback) here GoogleAuth is my project name.Is this valid or not??
ReplyDelete
Replies
Unknown20 March 2017 at 06:00
sir getting error
Server returned HTTP response code: 400 for URL: https://accounts.google.com/o/oauth2/token

Please help... where is there error can you tell me
ReplyDelete
Replies
Unknown20 March 2017 at 06:09
I am getting the same error. Please explain

entering doGet
java.io.IOException: Server returned HTTP response code: 400 for URL: https://accounts.google.com/o/oauth2/token
leaving doGet please help me
ReplyDelete
Replies
Unknown13 April 2017 at 20:59
I have an error "HTTP Status 500 - java.lang.NullPointerException" ! help me
ReplyDelete
Replies
Unknown20 June 2017 at 02:23
sir can you give me the netbeans realated project

ReplyDelete
Replies
Unknown22 June 2017 at 02:45
hello,
when i try to run your code using my app id and redirect uri, i am getting a blank screen in response(oauth2callback). can u please tell me the reason for it???
ReplyDelete
Replies
Unknown17 August 2017 at 01:53
hiii, i am trying with this code but it is showing a error of javax.servlet.ServletException: Servlet execution threw an exception
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

and
java.lang.NoClassDefFoundError: Could not initialize class com.javapapers.java.social.Google.GsonUtility
com.javapapers.java.social.Google.OAuth2Callback.doGet(OAuth2Callback.java:58)
javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
ReplyDelete
Replies
Unknown9 February 2018 at 02:22
I have created new project on Google Developer Console with below details:

public static final String CLIENT_ID = "697584815978-k8d8lm334gco5o01773cffe0lq3t1cvb.apps.googleusercontent.com";
public static final String CLIENT_SECRET = "_EzSu0M80LXL6m3XTDoCufmU";
public static final String REDIRECT_URL = "http://localhost:8080/GoogleLoginDemo";

The Auth URL get Users Email Address is below:
https://accounts.google.com/o/oauth2/auth?scope=email&redirect_uri=http://demo.darshanlibrary.com/oauth2callback&response_type=code&client_id=697584815978-k8d8lm334gco5o01773cffe0lq3t1cvb.apps.googleusercontent.com&approval_prompt=force

After this, i am getting "Allow" option on explorer page, when i click on ALoow:

Getting below token:
http://demo.darshanlibrary.com/oauth2callback?code=4/AAAzk7MLfUcfkVMJtis8f0brVs8edUC4e631s1Hm1O_R6UfDiWh1frMx8yDgHKmn-cOvnXDjkLv7bw5v5bpQQ4s#

This page can’t be displayed

•Make sure the web address http://demo.darshanlibrary.com is correct.
•Look for the page with your search engine.
•Refresh the page in a few minutes.

Please let me know what i am doing wrong?
ReplyDelete
Replies
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Unknown18 June 2019 at 05:17
please share code
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