• A simplified implementation of the network objects of Birrel.

• Developed mainly for pedagogical purposes by L. Mateu.

• All the classes are provided by the package netobj.

• The development of the package took just two-weeks.

Restrictions

• Does not provides a garbage collector, though it is simple to add it.

• Usable, but does not provide a stub/skeleton generator.

• No security manager, so does not support dynamic class loading.

• Not fully debugged.

Description

• The remote methods provided by network objects must be encapsulated on a network interface.

• A network interface is any interface being a subtype of the interface NetObj (equivalent to the Remote interface of RMI).

• Concrete object classes must be subclass of ConcreteNetObj (equivalent to the UnicastRemoteServer class of RMI).

• A concrete object can be referenced remotely only through variables declared as any of the network interfaces implemented by the concrete object.

• All remote methods must throw the exception NetException (equivalent to RemoteException in RMI).

Parameter passing and value returning

• Primitive types are passed by value.

• Network objects are passed by reference (remote references).

• Serializable objects are passed by deep copy.

• Each object is trasmitted only once.

• Recursive data structures don't loop forever.

Importing and Exporting Network Objects

• A Java process is identified by the hostname where it runs and the socket port where it serves remote requests.

• The programmer may specify which socket port to use for serving remote requests.

• Network objects can be exported by giving them a name.

• A network object can be imported by specifying its name and the identifier of the Java process where it lives.

• There is no equivalent to the rmiregistry, but it is simple to write one.

Writing stubs and skeletons

• The package provides the classes ConcreteNetObjStub and ConcreteNetObjSkel for implementing stubs and skeletons.

• Both classes provide useful methods to send and receive parameters and to return a value.

• The stub class must be subclass of ConcreteNetObjStub and be named as the name of the class of the concrete object plus the suffix Stub.

• The stub class must implement also the network interfaces supported by the concrete object.

• The skeleton class must be a subclass of ConcreteNetObjSkel and be named as the name of the class of the concrete object plus the suffix Skel.

• Don't worry, I won't ask you to program the stub generator. So you will have to write stubs and skeletons by hand.