CORBA BASICS
This are the important core terms corba specifies:
ORB Core:-
The purpose of ORB is to deliver requests to objects and return any output
values back to client.Clients need not know where the objects reside on
network,how they communicate,how they are implemented,how they are stored,nor
how they execute. Before a client issues a request it must hold an object
reference for that object. The ORB uses this to identify and locate objects
so that it can direct requests to them. When the referred object exists,
the ORB allows the holder of the object reference to request service from
it.
* Static invocation via interface-specific (client)stubs
* Dynamic invocation via the ORB Dynamic Invocation Interface
Regardless of the method, when client makes a request ORB locates the
desired object,activates it if is not executing already, and delivers request.
The object performs the requested service and returns any output back to
ORB which then returns it to client.
IDL:-
The Object reference although identifies a particular object, it does not
necessarily describe about the object's interface. Before a client makes
use of an object, it must know what service it provides. For this purpose
of publishing the interfaces an object supports IDL is used. It provides
basic datatypes (short,long,float,double,boolean),constructed datatypes(struct,union)
and template types(sequence,string). These are used in operation declarations
to define argument types and return types. Operations are used ininterface
declarations to define the service provided by objects.
Inheritance is allowed to limited extent. Derived interfaces inherit
the operations and types defined in their basic interface. But operations
cannot be redeclared in derived interface. There is nothing like implementation
inhertiance. IDL Compilers translate IDL language constructs into specific
programming language.
ObjectAdapter:-
OA is one through which object implementation accesses services provided
by ORB. Generation&Interpretatin of object reference,method invocation
security of interactions,object&implementation activation/decativation,mapping
object reference to implementation and registration of implementation.
Interface Repository:-
It is a service that provides peristent objects that represent IDL information
(in a form available at runtime). using IR it is possible to encounter
an object whose interface was not known when program was compiled, yet
able to determine what operations are valid on the object and make an invocation
on it.
It is a common place to store additional information associated with
interfaces associated with interfaces to ORB objects. (debugging information,
libraries of stubs or skeletons, routines that can format or browse particular
kind of objects etc., might be associated with IR).
Dynamic Invocation Interface (DII):-
An interface is also avl. that allows that dynamic construction of object
invocations, that is,rather than calling a stub routine that is specific
to a particular operation on a particular object, a client may specify
the object to be invoked, the operation to be performed and the set of
parameters for the operation through a call or sequence of calls. The client
code must supply information about the operation to be performed and the
types of the parameters being passed (perhaps from IR or other runtime
source).
Dynamic Skeletcon Interface (DSI):-
An interface which allows dynamic handling of object invocations. Rather
than being accessed through a skeleton that is specific to a particular
operation, an object's implementation is reached through an interface that
provides access to the operation and parameters in a manner analogous to
the client side's DII. static knowledge of those parameters or dynamic
knowledge ( thru IR) may be also used, to determine the parameters.
Quick Start of CORBA Application
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