I have a web application developed using Java (Java EE), spring & Hibernate. We are planning to use Apache Shiro for role & access management. One of our client requirement is to use some CMS functionality along with the web application, for which Drupal has been selected. Since all the users are created in the Java based web application we would like to enable Single Sign on between the Java web app and Drupal.
With the SSO enabled users of the web application should be able to access the pages (static content, blog etc.) created in Drupal.
Your best option would probably be to use CAS to handle SSO for both Drupal and Shiro. Drupal has a CAS module and Shiro can also be configured as a CAS client. You haven't provided any details in regard to exactly how your user accounts are maintained, but ideally that sort of data would be kept in a directory system such as OpenLDAP or Active Directory.