Combining a one-time "provisioning" process with JSF? - facebook

Question

Let me preface this by admitting that this is my first webapp and first experience with JSF, so I've probably made some poor design decisions.
Here's what I'm trying to do:
I have a webapp using JSF 2.0, which is accessible through a Facebook canvas. This webapp allows a user to view/manipulate data from a database of sensor readings. On the very first time the Facebook user accesses my app, I ask the user to enter login credentials for the database, then send the user to the home page. Thereafter, the user should always go straight to the home page, since I associate the user's FB id with the database user profile.
Current implementation:
I have the Facebook canvas URL going to a servlet. This servlet checks the signed_request parameter passed by Facebook to get the user ID, and then looks in the database to see if the user has already completed the provisioning process. If the user has done so, he is redirected to the application home page.
The problem:
Most of my logic to do these checks currently exists within a managed bean (session-scoped). To use the bean within the servlet, I'm manually instantiating the bean and adding it to the session, since the JSF framework hasn't had a chance to create it yet. As my system is getting more complicated, this is causing problems due to dependencies between the various beans. Also, it seems like a generally bad approach to the problem.
Solutions? From my web searching, it sounds like there might be several ways to do this. One way would be to set the canvas to a JSF landing page, where a managed bean would grab the signed_request parameter and validate that the user has completed the provisioning step. From there, the bean would forward to the proper page. Another possibility might be to have an eager bean that does the same thing, but this seems "wrong".
What's the best way to resolve this and adhere to "proper" JSF paradigms?
Thanks in advance!

Answer 1

There are a number of different ways that this can be handled. The JSF landing page is one idea and the eager bean are some ways that this can be handled.
If you ignore the fact that you are integrating with Facebook then ultimately you are trying to solve an authentication and authorization problem. Facebook is handling your authentication, and telling your web application what the identity of a user is, and it is your web app's job to remember that person's identity throughout the session, and authorize this person to visit the requested page.
I have implemented it before where I had all of my managed beans extend a BaseBean class that on creation and initialization checked for the existence of a specific SessionScoped bean that contained the user identitification information. If this bean did not exist or was not authorized to access this bean then I would redirect. The problem with this approach was that it authorized only the use of managed beans, and not pages.
Another approach I had was to utilize a servlet filter that would essentially check every page request and look for the session scoped bean that contained the currently authenticated user. If this wasn't found then I would look for the specific request parameters and authenticate and create the session bean, and if that didn't exist would redirect to an Unauthorized page.
This approach worked well until I realized that Authentication and Authorization of Java web applications is a well understood and near universal problem. After a little bit of looking and research I discovered that security frameworks like Spring Security 3 can indeed be integrated into JSF and handle nearly all of the complexity of complex authentication and authorization. You could very easily integrate a custom Facebook authentication handler for Spring Security and control access by user role to the individual page level, all from XML configuration. It is highly worth looking into if you have the time to learn something new.