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CORBA Continued

CORBA Continued. CORBA Terminology. ORB - Object Request Broker IR – Implementation Repository IDL – Interface Definition Language OA,BOA,POA – Object Adaptor, Basic Object Adaptor, Portable Object Adaptor Object Services. A Description of The ORB http://www.omg.org/corba/whatiscorba.html.

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CORBA Continued

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  1. CORBA Continued Netprog: More Corba

  2. CORBA Terminology • ORB - Object Request Broker • IR – Implementation Repository • IDL – Interface Definition Language • OA,BOA,POA – Object Adaptor, Basic Object Adaptor, Portable Object Adaptor • Object Services Netprog: More Corba

  3. A Description of The ORBhttp://www.omg.org/corba/whatiscorba.html "The (ORB) is the middleware that establishes the client-server relationships between objects. Using an ORB, client can transparently invoke a method on a server object, which can be on the same machine or across a network." Netprog: More Corba

  4. A Picture from OMGwww.omg.org/gettingstarted/corbafaq.htm Netprog: More Corba

  5. ORB Differences • The specification of the functionality of an ORB is not a complete implementation description. • Many of the details are left up to the implementor. • Every Vendor does things differently. • You write code to work with a specific ORB. Netprog: More Corba

  6. Inter-ORB Protocol • There is support for connecting ORBs. • The most significant support is the Internet Inter-Orb Protocol (IIOP) • Specifies the details of communication (bridging) between ORBs. Netprog: More Corba

  7. Multiple ORB Picturewww.omg.org/gettingstarted/corbafaq.htm Netprog: More Corba

  8. Call Semantics (part of Corba Object Model - 1.2.8.5 Execution Semantics) "Two styles of execution semantics are defined by the object model: • At-most-once: if an operation request returns successfully, it was performed exactly once; if it returns an exception indication, it was performed at-most-once. • Best-effort: a best-effort operation is a request-only operation (i.e., it cannot return any results and the requester never synchronizes with the completion, if any, of the request)." Netprog: More Corba

  9. IDL • Used to describe "interfaces" • similar to RPC .x file • Object Oriented. • Mappings to many languages. Netprog: More Corba

  10. General Layout of IDL File Organizational group moduleidentifier { type,constant & exception declarations interfaceidentifier : base { attribute declarations type identifier(parameters) raises exception; type identifier(parameters) raises exception; … } Corba Class Corba Methods Netprog: More Corba

  11. Sample IDL(from Essential Dist. Object Survival Guide) Module MyAnimals { interface Dog:Pet,Animal { attribute integer age; exception NotInterested(string explanation); void Bark(in short how_long) raises(NotInterested); void Sit(in string where) raises(NotInterested); } interface Cat:Animal { void Eat(); } } Netprog: More Corba

  12. IDL from Mico Example interface Account { void deposit(in unsigned long amount); void withdraw(in unsigned long amount); long balance(); }; Netprog: More Corba

  13. Object Adaptors • Corba includes specification of mechanisms for how the server-side ORB should react to requests. • How to start up the server (or hand the request to the server). • Create object references. • BOA is simplest OA. Netprog: More Corba

  14. POA • Newer than BOA. • Supports lots of fancy stuff: • Persistent objects. • Threads. • So far I haven't heard of TOA, ZOA or OOA Netprog: More Corba

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