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Lesson 4The CORBA client
ObjectiveLearn more about CORBA Clients

CORBA Client(Stubs, Services)

In the previous lesson, we took a good look at how Stubs provide much of the functionality associated with CORBA to clients. The Slide Show below will expand on that knowledge as we learn more about CORBA clients.

1) Client Server 1 2) Client Server 2 3) Client Server 3 4) Client Server 4
  1. At the basic level, a CORBA Client simply wishes to obtain services
  2. The CORBA Stub does most of the work, so the client may remain simple.
  3. We have already started to explore the CORBA development proces
  4. The CORBA architect creates an IDL file, the Stub is produced when the IDL is run through an ORB vendors IDL pre-processor

Corba Consumer.
There may be times when the client developer does not have access to the Stub when the client is created or, in a broader view, a client may not want to make CORBA requests of a server that does not exist when the client is written. These problems are solved by the CORBA Specified Dynamic Invocation Interface (DII).
The DII allows a client to learn at runtime about the operations supported by a server, and to create requests, without a Stub, that are sent directly to the ORB. From there, the requests are forwarded to the server.

The client queries the CORBA-specified <em>Interface Repository</em> to retrieve data about the interface and its operations.
Figure 3.4.1: The client queries the CORBA-specified Interface Repository to retrieve data about the interface and its operations.

Communication between the Dynamic Invocation Interface and the Client
Figure 3.4.2: Communication between the Dynamic Invocation Interface and the Client

The client then builds a raw request, submits the request directly to the ORB via the DII (which takes the place of the Stub), and the request is handled as normal by the ORB.

Client communicates with server by means of 1) Stub and 2) Dynamic Invocation Interface.
Figure 3.4.3: Client communicates with server by means of 1) Stub and 2) Dynamic Invocation Interface.

CORBA clients may communicate with servers using Stubs or DII, or a combination of the two.
Now that we understand the fundamentals of how a CORBA client is constructed and used, we will next focus on the server side of CORBA.