CORBA The Interface Definition Language

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CORBAThe Interface Definition Language
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Appendix 1

• Interface Definition Language
• IDL to Java Mapping

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1998 CTIT, Nikolay Diakov
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Types, Modules Scoping

• What are Types for?
• Every variable or parameter must be typed
• There is a special type any
• What is Scoping for?
• Scope to module, interface, operation
• Scoping operator "" imports

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• 1. IDL Basic (Primitive) Types
• Integer
• short, long, long long
• signed unsigned
• Floating point
• float, double, long double, fixed
• char, boolean, octet
• The special Any
• CORBA Object Reference

1998 CTIT, Nikolay Diakov
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• 2. IDL Structured (Constructed) Types
• Structs
• Unions
• Enums
• Sequences
• Strings
• Arrays

1998 CTIT, Nikolay Diakov
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Struct Declaration Example
struct PaymentOrder float Price string GoodyN
ame string Authorization
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Enum, struct, sequence declarations example
enum ItemTypes food, clothes, other struct
GOODSinfo long id StoreAccess StoreAccessRe
ference float TotalSales float TotalTaxes
typedef sequence ltGOODSinfogt GOODSlist
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• 3. Interfaces, Operations, Attributes
• Interface
• groups operations
• it is the unit of inheritance
• and can extend one or more already defined
  interfaces
• Operation
• has a return value, operation name, list of
  parameters, exceptions, oneway declaration
• Attribute - a special data holder variable with
  access methods

1998 CTIT, Nikolay Diakov
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Interface Example
Module OnlineOrdersystem typedef string
OrderNameType interface Identification
typedef short PIN long doPIN (in long uid,
in PIN cardpin, out OrderNameType
name)
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• 4. Name Scoping and Inheritance
• In IDL you can derive a new interface from one or
  more existing interfaces - this way inheriting
  all their elements
• And you can extend with new elements
• constants, types, attributes, operations
• interface BasicOrders
• long BasicPayment (in long arg1)
• interface ExtendedOrdersBasicOrders
• void AdvancePaymentSystem (in short arg2)

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• Exceptions
• CORBA declares some standard exceptions
• Custom exception can be defined this way

exception CreditCardInvalid ORDEROrderNumber
item
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CORBAIDL to Programming Language Mapping
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CORBAIDL to Programming Language Mapping
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• Translates from OMG IDL constructs to programming
  language constructs
• Special IDL compiler generate stubs for the
  client and skeletons for the server objects

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CORBAIDL to Java Mapping
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• IDL Modules map to Java Packages
• Interfaces map to public Java Interfaces
  Helper and Holder Java classes
• IDL Operations map to Java methods
• the integral types (Integer, float) map to the
  corresponding Java integral types
• exceptions map to Java exceptions

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CORBAIDL to Java Mapping (Example)
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And, a slightly enhanced IDL Declaration (to show
parameter passing) interface example1 long
op1 ( in long arg1, out long arg2, inout
long arg3) produces the following Java public
interface example1 int op1 ( int
arg1, IntHolder arg2, IntHolder arg3)
1998 CTIT, Nikolay Diakov