Integrating Google Spreadsheets - Part 2

In my last post, I elaborated on how I have used the Google Documents List Data API and the Spreadsheets Data API to integrate Google Docs in my application. In this post, I will explain on how I provided online access to the spreadsheets to my application users. The users were not required to sign on to Google manually, I used SAML to sign them on and access the docs. To read more about how SAML works with Google, go through this article. The article is very helpful and
Before you make any changes in the application, you need to have administrator access to the Google apps account. You can enable provisioning API for programmatic account mgmt(I didn't). You need the following information about your application:
1. Login page
2. Logout page
3. Change password page
4. Certificate file (more info here)

Once you have the above information, log on to your Google Apps account. Go to the "Advanced tools" tab and click on "Set up single sign-on (SSO)". Once on the SSO page, enable SSO, enter the page details and upload the certificate file. Remember to save the changes. You can also create more user accounts to allow for better access control and user management. That's pretty much it on configuring the Google Apps for SSO. After you have saved your changes, go to the Dashboard and copy the Docs Service url (should be http://docs.google.com/a/). Try hitting the url, if you are redirected to the login page you entered in the SSO setup, things are going fine!

Now you need to provide implementation for SAML in your application. Go through this article, it has reference implementation for SAML-based SSO for the docs. Download the code and run the application. It will help you understand the way SAML works by printing the request, response, reference URLs and so on.
I used the example as the base reference in my development. I utilized the util classes AS-IS, and wrote the servlet implementation for the ProcessResponseServlet. The login() method needs to be updated to utilize your application's authentication mechanism. I also put in custom implementations in the service(doGet() and doPost()) method for the SSO process.

After these changes are made, you are pretty much done. Deploy your application, hit the Docs Service url again, it should redirect you to the login page, enter your applications credentials and your should be redirected to the Google Docs page.

Just as a side note, in my implementation, users had to be already authenticated to my application to be able access the Google Docs. I attached one Google user account with a group of my application users. When a user tried to access Google Docs, my SAML response servlet picked the Google account associated with the user and processed the SAML response.