Google Spreadsheet API Connecting with OAuth2 JAVA Example

What is OAuth2 and things you should know before writing your source code?

OAuth, is an open protocol that aims to standardize the way desktop and web applications access a user's private data. OAuth provides a means of performing API authentication in a standard and secure fashion. As programmers, we're taught to reuse code wherever possible. OAuth will help developers reduce the amount of duplicate code they write and make it easier to create tools that work with multiple services from a variety of different providers.

Here are the terms we are using in the OAuth world.

OAuth dance - Unofficial term to describe the full OAuth authentication/authorization process.

(OAuth) Request token - An initial token that lets Google know your application is requesting access to one of the Google Data APIs. The second step of the OAuth dance is for the user to manually grant access to their data. If this step is successful, the request token becomes authorized.

(OAuth) Access token - The last step of the dance is to exchange the authorized request token for an access token. Once your application has this token, a user won't need to go through the OAuth dance again, unless the token is revoked.

(OAuth) Endpoints - These are URIs required to authenticate an application and obtain an access token. 

 There are three total - one for each step of the OAuth process. Google's OAuth endpoints are:

Obtain a request token:	https://www.google.com/accounts/OAuthGetRequestToken
Authorize the request token:	https://www.google.com/accounts/OAuthAuthorizeToken
Upgrade to an access token:	https://www.google.com/accounts/OAuthGetAccessToken

(OAuth) Service Provider In the case of the Google Data APIs, this provider is Google. In general, the service provider is used to describe the website or web service that provides the OAuth endpoints. Another example of an OAuth service provider is MySpace.

(OAuth) Consumer The program requesting permission to access a user's data (i.e. your application). The OAuth protocol is flexible in that it allows for a wide variety of different types of clients (web, installed, desktop, mobile).

How to get the required token's from google (OAuth provider) ?

1. First you need to register your application with google api console at this url

https://code.google.com/apis/console

2. Create a new project for your application

3. Create a new OAuth2 Client ID by clicking the button and giving the required information.

4. Then click the create client ID button and that will create a Client ID and Client Secret for your application

How to access google spreadsheet api with a JAVA program?

Here is the complete JAVA source code with comments inside for accessing the google spreadsheet api with the token's you have received from the above step.

package org.samples.oauth2;

import java.io.IOException;

import java.net.MalformedURLException;

import java.net.URL;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import com.google.gdata.client.GoogleService;

import com.google.gdata.client.authn.oauth.GoogleOAuthHelper;

import com.google.gdata.client.authn.oauth.GoogleOAuthParameters;

import com.google.gdata.client.authn.oauth.OAuthException;

import com.google.gdata.client.authn.oauth.OAuthHmacSha1Signer;

import com.google.gdata.client.authn.oauth.OAuthRsaSha1Signer;

import com.google.gdata.client.authn.oauth.OAuthSigner;

import com.google.gdata.client.spreadsheet.SpreadsheetService;

import com.google.gdata.data.BaseEntry;

import com.google.gdata.data.BaseFeed;

import com.google.gdata.data.Feed;

import com.google.gdata.util.AuthenticationException;

import com.google.gdata.util.ServiceException;

/**

 * 

 * @author Chanaka Fernando

 * 

 * Class implemented for accessing google spreadsheet application programming interface (API) features related to authentication

 *

 */

public class OAuth2Sample {

  

 /**

  * Log in to Google, with the OAuth2 authentication

  * 

  * @param clientID client ID received from registering the application with Google

           * @param clientSecret client Secret received from registering the application with Google

  * @throws AuthenticationException if the service is unable to validate the

  *         oauth2 parameters.

  */

 public void loginOAuth2(String clientID, String clientSecret)

     throws AuthenticationException {

   String SCOPES = "https://docs.google.com/feeds https://spreadsheets.google.com/feeds";

   

   // STEP 1: Set up the OAuth objects

   // You first need to initialize a few OAuth-related objects.

   // GoogleOAuthParameters holds all the parameters related to OAuth.

   // OAuthSigner is responsible for signing the OAuth base string.

   GoogleOAuthParameters oauthParameters = new GoogleOAuthParameters();

   // Set your OAuth Consumer Key (which you can register at

   // https://www.google.com/accounts/ManageDomains).

   oauthParameters.setOAuthConsumerKey(clientID);

   // Initialize the OAuth Signer.  

   OAuthSigner signer = null;

   oauthParameters.setOAuthConsumerSecret(clientSecret);

   signer = new OAuthHmacSha1Signer();

   // Finally create a new GoogleOAuthHelperObject.  This is the object you

   // will use for all OAuth-related interaction.

   GoogleOAuthHelper oauthHelper = new GoogleOAuthHelper(signer);

   // STEP 2: Get the Authorization URL

   // Set the scope for this particular service.

   oauthParameters.setScope(SCOPES);

   // This method also makes a request to get the unauthorized request token,

   // and adds it to the oauthParameters object, along with the token secret

   // (if it is present).

   try {

oauthHelper.getUnauthorizedRequestToken(oauthParameters);

} catch (OAuthException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

   // Get the authorization url.  The user of your application must visit

   // this url in order to authorize with Google.  If you are building a

   // browser-based application, you can redirect the user to the authorization

   // url.

   String requestUrl = oauthHelper.createUserAuthorizationUrl(oauthParameters);

   System.out.println(requestUrl);

   System.out.println("Please visit the URL above to authorize your OAuth "

       + "request token.  Once that is complete, press any key to "

       + "continue...");

   try {

System.in.read();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

   // STEP 3: Get the Access Token

   // Once the user authorizes with Google, the request token can be exchanged

   // for a long-lived access token.  If you are building a browser-based

   // application, you should parse the incoming request token from the url and

   // set it in GoogleOAuthParameters before calling getAccessToken().

   String token = null;

try {

token = oauthHelper.getAccessToken(oauthParameters);

} catch (OAuthException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

   System.out.println("OAuth Access Token: " + token);

   System.out.println();

   // STEP 4: Make an OAuth authorized request to Google

   // Initialize the variables needed to make the request

   URL feedUrl = null;

try {

feedUrl = new URL("https://spreadsheets.google.com/feeds/spreadsheets/private/full");

} catch (MalformedURLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

   System.out.println("Sending request to " + feedUrl.toString());

   System.out.println();

   SpreadsheetService googleService =

       new SpreadsheetService("oauth-sample-app");

   // Set the OAuth credentials which were obtained from the step above.

   try {

googleService.setOAuthCredentials(oauthParameters, signer);

} catch (OAuthException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

   // Make the request to Google

   

   // Make a request to the API and get all spreadsheets.

   SpreadsheetFeed feed = googleService.getFeed(feedUrl, SpreadsheetFeed.class);

   List<SpreadsheetEntry> spreadsheets = feed.getEntries();

   

   System.out.println("Response Data:");

   System.out.println("=====================================================");

   if(spreadsheets != null) {

   

    // Iterate through all of the spreadsheets returned

    for (SpreadsheetEntry spreadsheet : spreadsheets) {

//Print the name of each spreadshet

    System.out.println(spreadsheet.getTitle().getPlainText());

    }

   }

     System.out.println("=====================================================");

   System.out.println();

  

   ////////////////////////////////////////////////////////////////////////////

   // STEP 5: Revoke the OAuth token

   ////////////////////////////////////////////////////////////////////////////

   System.out.println("Revoking OAuth Token...");

   try {

oauthHelper.revokeToken(oauthParameters);

} catch (OAuthException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

   System.out.println("OAuth Token revoked...");

 }

}

With the above code you can access the Google Spreadsheet API with OAuth2 authentication mechanism with your JAVA program.

Cheers !!!!