Invocation semantics

When netlet A invokes a method on an interface exported by netlet B, either the method returns or an exception is thrown. The passing of arguments and return values follows the Java RMI semantics⁸:

• Primitive types are copied.
• Objects that implement org.jtrix.service.IRemote are proxied. By default, the proxy has the type declared in the signature. Using org.jtrix.base.FacetHandle, the proxy type can be controlled at run-time.
• Objects that do not implement IRemote but implement java.io.Serializable are transmitted in serialised form. Serialization requires the Class of the passed implementation object to be the same in both parties' codebases.
• Objects of other types cannot be passed between netlets.
• Exceptions are always checked for equality with the exception classes declared in the signature. If an undeclared exception is thrown (even if it is a subclass of a declared exception), org.jtrix.base.InternalError is thrown instead.

As an optimisation, instances of org.jtrix.base.Immutable that are held by the node can be passed directly.

The node may limit the number of active invocations into a netlet or into the node.

Mediation introduces new error conditions. A new exception type is defined to indicate those:

org.jtrix.base.MediationError