rmi

Master Java - Level 2/ Session 11 / 1 of 14

Remote Method Invocation (RMI)

Session 11

Master Java - Level 2/ Session 11/ 2 of 14

Session Objectives Describe the Java Distributed Model

Analyse RMI Architeture

Discuss RMI packages

Explain how to implement RMI client and server


Distributed Application A Distributed application is an application whose

processing is distributed across multiple networked computers.

The various models that can be used for developing distributed applications Distributed Component Object Model(DCOM) Common Object Request Broker Architecture(CORBA) Remote Method Invocation(RMI)


Remote Method Invocation (RMI)

Java Virtual MachineJava Virtual Machine

Client ObjectClient Object

Java Virtual MachineJava Virtual Machine

Server ObjectServer ObjectTCP

The distributed object model used by Java allows objects in one JVM to invoke methods of objects in a separate JVM. This is known as RMI.


RMI System Layers

The RMI system consists of three layers in its architecture:

Stub/Skeleton Layer

Remote Reference Layer

Transport Layer


RMI Architecture

Java Virtual Machine

Client Object

TCP

Object ‘S’ Stub

Remote ReferenceLayer


TransportLayerTransportLayer

Java Virtual Machine

Server Object ‘S’

Object ‘S’ Skeleton



TransportLayerTransportLayer


Remote Method Invocation API

The five packages in RMI API are: java.rmi java.rmi.registry java.rmi.server java.rmi.activation java.rmi.dgc

We shall be examining the first three in detail


The java.rmi Package The java.rmi package declares

The Remote interface

The MarshalledObject class

The Naming class

The RMISecurityManager class

A number of exceptions that are used with remote method invocations


The java.rmi.registry Package

The interfaces and class of the java.rmi.registry package are used to handle remote objects by name and also to register those remote objects

The java.rmi.registry package provides

The Registry interface

The RegistryHandler interface

The LocateRegistry class.


The java.rmi.server Package

The java.rmi.server package supports both client and server aspects of RMI like a class implementation of Remote interface, client stub and server skeleton

Classes and Interfaces declared are :

RemoteObject class

RemoteServer class

UnicastRemoteObject class

RemoteStub class

Skeleton interface

RMIClassLoader class

RMISocketFactory class


Implementing RMI

Implement RMI server Create Remote Interface Create a class that implements the remote interface Create stub and skeleton classes Copy Remote interface and stub to client Create and register remote objcet

Implement the RMI client Call the remote interface by using the ‘lookup()’ method of the Naming class.


RMI flow - I

Server Virtual MachineServer Virtual MachineClient Virtual MachineClient Virtual Machine

Client

Stub

Remote Object

Skeleton

RegistryRegistry VirtualVirtual MachineMachine

Server

Remote ObjectRegistered

1

21. Server Creates Remote1. Server Creates Remote object.object.

2. Server Registers Remote2. Server Registers Remote object with RMI registryobject with RMI registry


RMI flow - II

3. Client requests object from3. Client requests object from registryregistry

4. Registry returns remote 4. Registry returns remote reference through interfacereference through interface


Client

Stub

Remote Object

Skeleton

Registry Virtual MachineRegistry Virtual Machine

Server


3 4


RMI flow - III

5. Client invokes stub method5. Client invokes stub method

6. Stub talks to skeleton6. Stub talks to skeleton

7. Skeleton invokes remote 7. Skeleton invokes remote object method.object method.


Client

Stub

Remote Object

Skeleton

Registry Virtual MachineRegistry Virtual Machine

Server


5 6

7

rmi

Technology

remote method invocation

remote interface

registry package

distributed application

master java

naming class

rmi flow

class