Implementing IHelloFacet

As already mentioned, our service will have to implement the IHelloFacet. It's not complicated.

It's worth taking this opportunity to talk again about security. (You can skip this bit if you want.) Although the client netlet uses this interface it doesn't use any of our implementation. Our implementation of IHelloFacet stays entirely within our codebase, thanks to the mediator. Whenever the client invokes getMessage() the call comes back to our access point netlet which deals with it, so that means the service is only usable as long as our acess point netlet is alive, and we cannot use nasty techniques to compromise the client: we're completely isolated from it.