What is CORBA?
CORBA or Common
Object Request Broker Architecture is an industry standard which introduced by
Object Management Group (a consortium consist of 700 companies and
organizations) to aid in distributed objects programming. The CORBA provided in
a standard programming language, such as the Java or C++. CORBA is composed of major
components: ORB,
IDL, dynamic invocation interface (DII), dynamic skeleton interface (DSI), interface
repositories (IR), and object adapters (OA).
1. ORB (Object Request Broker) ,the heart of
CORBA is the distributed service that find the object implementation for the
request, prepare the object implementation to receive the request and communicates
the data making up the request. Client can use the same request mechanism and
the CORBA object regardless of where the object is located. The ORB implements
programming language independence for the request. The request which send by
the client can be written in different programming language.
CORBA Products:
i) Java 2 ORB (Sun’s Java 2 SDK)
ii) VisiBroker for Java (Inprise Corporation.
VisiBroker also embedded in
other
products such as Netscape Communicator)
iii) ORBIX (Iona
Technologies)
iv) WebSphere
(Application server from IBM)
v) Orbacus (Iona Technologies)
Examples ORBs
implementations:
•Client- and Implementation-resident ORB
•Client- and Implementation-resident ORB
•Server-based ORB
•System-based ORB
•Library-based
ORB
2. IDL( Interface Definition Language ) is used to
define an object interface and types of objects. IDL allows to define the
operations and attributes that an object supports. Basic IDL data
types such as long, short, string and float. IDL declarations are compiled with
an IDL compiler and converted to their associated representations in the target
programming languages according to the standard language binding.
3. DII(Dynamic Invocation Interface) allows client
applications to use server objects without know the type of those objects at
compile time. It allows a client to obtain an instance of a CORBA object and
make invocations on that object by dynamically constructing requests. DII uses
the interface repository to validate and retrieve the signature of the
operation on which a request is made.
4. DSI (Dynamic
Skeleton Interface) allows servers to be written without
having skeletons, or compile-time knowledge, for the objects being implemented.
It support the implementation of gateways between ORBs which utilize different
communication protocols.
5. Using IR( Interface Repositories), a client
should be able to locate an object that is unknown at
compile time, find information about its interface, then build a request to be
forwarded through the ORB.
6. OA( Object Adapter ) is
the primary way that an object implementation accesses services provided by the
ORB such as object reference generation and interpretation, method invocation,
security of interactions, and object and implementation activation and
deactivation.
•Object adapters
are responsible for the following functions:
–Generation and interpretation
of object references
–Method
invocation
–Security of
interactions
–Object and
implementation activation and deactivation
–Mapping object
references to the corresponding object implementations
–Registration of
implementations
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