I would like to describe a use case for Hibernate, and get some feedback as to
whether it's possible as described, or whether I need to consider a different
approach.

Our application operates in multiple instances of the same database schema for
purposes of isolation, as well as a second schema that is global to all
participators. A single user is granted access to parts of all of these
schemas to perform operations that must take effect on all of them.

So, we have this arrangement:

SchemaA: r/w accessible to UserA, r/o accessible to UsersB[0..N]
SchemaB[0..N]: r/w accessible to UsersB[0..N]

UserC with access to A, B[0..N]

This arrangement is a business requirement, so I can't really change it.

Additionally, the names of the UserB class users are not known at configuration
or compilation time, they are provided at runtime by data, and new ones may be
created at any time without an application restart; the schema is instantiated
by an external process.

So, we have two scenarios:

1. Logged in as UserB[m]. Accesses to tables within SchemaB do not need schema
qualification, acceses to SchemaA require qualification as UserA.TABLE.

2. Logged in as UserC. All accesses require schema name qualification,
and the specific instance of UserB that must be used is determined from
current state.

Is there any way whatsoever to configure a single SessionFactory to do this?
I know that I can create a separate SessionFactory for each UserB and for
UserC, but that makes for a very expensive delay the first time a
SessionFactory is initialized. The thing here is that each instance of SchemaB
is identical. It seems like a waste to configure a separate SessionFactory
for each of them.

Any advice on how to do this would be welcome. If it makes a difference, this
is a J2SE application.