4003-707 Advanced Java Programming

all, section 18.45.

18.45. Dynamic Class Loading

RMI allows parameters, return values and exceptions passed in RMI calls to be any object that is serializable. RMI uses the object serialization mechanism to transmit data from one virtual machine to another and also annotates the call stream with the appropriate location information so that the class definition files can be loaded at the receiver.

When parameters and return values for a remote method invocation are unmarshalled to become live objects in the receiving VM, class definitions are required for all of the types of objects in the stream. The unmarshalling process first attempts to resolve classes by name in its local class loading context (the context class loader of the current thread). RMI also provides a facility for dynamically loading the class definitions for the actual types of objects passed as parameters and return values for remote method invocations from network locations specified by the transmitting endpoint. This includes the dynamic downloading of remote stub classes corresponding to particular remote object implementation classes (and used to contain remote references) as well as any other type that is passed by value in RMI calls, such as the subclass of a declared parameter type, that is not already available in the class loading context of the unmarshalling side.

To support dynamic class loading, the RMI runtime uses special subclasses of java/io.ObjectOutputStream and java/io.ObjectInputStream for the marshal streams that it uses for marshalling and unmarshalling RMI parameters and return values.