Remote Method Inovcation

							There are several ways of developing distributed applications.

 RMI is also one way to transfer data from one host to another by
  using sockets

 RMI is a specification that enables Java Virtual Machine( JVM)
  to invoke methods inn an object located in another Java Virtual
  Machine( JVM).

 These two Java Virtual Machines( JVMs), could be running on
  different computer or running as separate process on the same
  computer.

 RMI is implemented on the middle-tier of the three-tier
  architecture framework, thereby facilitating the programmers to
  invoke distributed components across a networked environment.
 Sun introduced RMI as an easy alternative to complex
  coding invoked in server-socket programming .

 For using RMI, the programmer need not know socket
  programming or multi-threading and needs to solely
  concentration on the developing the business logic.
Components of a Distributed RMI Application


  A Distributed RMI Application has TWO
  components
 RMI Server
 RMI Client
 The RMI server contains the object whose methods are to
  be invoked remotely.

 The server creates several remote objects and makes
  reference of these objects in the RMI registry.

 The RMI registry is a service that runs on the RMI server.

 The remote objects created by the server are registered by
  the objects’ unique name in this registry.

 The client gets the reference of one or more remote objects
  from the RMI registry by looking up the object name.

 The client then invoked the methods on the remote
  object(s) to access the services of the remote object(s)
                         Server
                                                            Object
                                               Objects      Registered



                                             RMI Registry




                    Searches for the remote Object
Client




         Functioning of Applications in RMI
 The RMI Architecture
The RMI architecture consists of three layers:
Stub/Skeleton Layer
Remote Reference Layer
Transport Layer
                                                    JVM
       JVM

      Client                                     Server




       Stub                                      Skeleton




Remote Reference Layer                      Remote Reference Layer




   Transport Layer                             Transport Layer




                     The RMI Architecture
Stub/Skeleton Layer
 The Stub/Skeleton Layer listens to the method calls made by the
  client and redirects these to the remote RMI services on the server
  side.
 This layer consists of Stub and Skeleton.
 To invoke methods of the remote object, the request on the client-
  side starts with the Stub.
 A Stub is a client-side proxy representing the remote object.
 It is referred as any other local object by programs running on the
  client and provides methods of a remote object.
 The Stub communicates the method invocations to the remote
  object through a Skeleton that is implemented on to server.
 The Skeleton is a server-side proxy that communicates with the Stub
  by reading the parameters for the method call, making the call to
  the remote services implementation object, accepting the return
  value, and then writing the return value.