Accessing remote object after unbind

Question

I'm working on a server, multi-client application where I want the client to throw an exception whenever the client cannot reach the server. I thought the cases where this may occur were the following:
-- The RMI registry is no longer running on the server machine.
-- The server object is no longer present (has become null)
-- The server object has been removed from the RMI registry through Naming.unbind().
The final case has caused me the most fits during testing. I've noticed that if a client has a remote reference to the server object, the client can still make method calls on it even if the server object no longer exists within the RMI registry.
One fix would be to have the client obtain a remote reference to the server object before any remote method call; receiving a NotBoundException if the server object has been removed from the registry.
Yet is there another way that a client can notice if the server object no longer exists within RMI registry?
Thanks.

Answer 1

-- The RMI registry is no longer running on the
server machine.
-- The server object is no longer present (has become
null)This can't happen. Naming.lookup() never return null, they throw NotBoundException instead (even if someone at the server deliberately binds null).
-- The server object has been removed from the RMI
registry through Naming.unbind().There is at least one more more case you need to consider:
-- the remote object has been unexported but left in the Registry (or the client still has a reference from before): this will cause a NoSuchObjectException.
The final case has caused me the most fits during
testing. I've noticed that if a client has a remote
reference to the server object, the client can still
make method calls on it even if the server object no
longer exists within the RMI registry.I'm not clear about your objective here. This can certainly happen but if you're just trying to enumerate the possible exceptions this isn't even an exception.