OSGi happy family: UserAdmin

Bundles, wiring, life-cycle and services architecture are not the only part of OSGi specification. Although they're "Core", standard covers also a number of services that we most likely gonna need - like HTTP, position (GPS!), preferences or user management.

User Admin Service comes into action whenever our application is run by multiple users with different privileges. It brings notion of Roles, Users and Groups, who have their properties and credentials. User can perform actions on behalf of selected role if he's one of that role's basic members and has all memberships required by that role. Authorization code looks like this:

User user = (User) UserAdmin.getUser("jacek");
Authorization auth = userAdmin.getAuthorization(user);
if (auth.hasRole("CVS_USERS")) {
 // ...
}

Naturally users can come and go at any time, thus we're given actually two services: one for querying users (UserAdmin) and another to track any changes (UserAdminListener).
Generic specification allows for wide range of implementations behind UserAdmin. Equinox's one lays on Preferences (yet another OSGi service).
However UserAdmin is functionally very similar to JAAS, JAAS depends on JDK1.3 which is still to high barier for OSGi.