check if bean exists

Hello

I am using a bean as part of my login procedures if the user successfully logins then a loginBean is instantiated and populated with the appropriate data, the rest of my site is a series of jsp's and java servlets. How do I ensure the user has logged in and populated the loginBean before they get to any of the pages below the login page. I assume it involves a redirect and I need to test if the loginBean exists within my session. So if the user calls a page that is below the login page they are redirected to the login page if they have not successfully logged in at this stage. I need to be able to check in servlets and jsp's I think. Any suggestions.

Thanks

Jake