Object Request Broker (ORB)

1
A First Java ORB Application

• Object Request Broker (ORB)
• This is the object manager in CORBA
• Mechanisms for specifying interfaces
• Interface Definition Language (IDL) - for static
  interface definitions
• Dynamic Invocation Interface (DII) - lets clients
  access interfaces as first-class objects at
  run-time from an Interface Repository.
• Internet Inter-Orb Protocol (IIOP)
• A binary protocol for communication between ORBs.
• Was added in CORBA 2.0

2
CORBA Application Development Process

• Write IDL
• Compile IDL
• Identify the IDL compiler-generated interfaces
  and classes that we need
• Write code to initialize the ORB and inform it of
  any CORBA objects created
• Compile all the generated code and application
  code
• Run the application

3
Building CORBA Application

• Hello world

4
Interface Specification

• // idl file
• module helloWorld
• interface GoodDay
• string hello()
• Compile the idl file, generate the following set
  of files
• GoodDay.java
• GoodDayHolder.java GoodDayHelper.java
• _GoodDayStub.java GoodDayPOA.java
• GoodDayOperations.java GoodDayPOATie.java

5
Generated Files

• GoodDay.java java interface mapped from IDL
  interface
• GoodDayHolder provide support to handle IDL
  inout and out parameters
• GoodDayHelper contains supporting methods, most
  used one is narrow()
• _GoodDayStub.java client side stub code
• GoodDayPOA.java contains the skeleton code that
  is used with POA
• GoodDayOperations.java and GoodDayPOATie.java
  contain skeleton code that are used with Tie
  approach

6
Client Side

• Initialize the CORBA environment obtain a
  reference to the ORB
• Obtain an object reference for the object on
  which to invoke operations
• Invoke operation and process the results
• Example
• Code from Ch. 4

7
Server Side

• Initialize the CORBA environment, the ORB (the
  same as client side)
• Create implementation object
• Make the implementation object accessible by
  clients
• Listens for events
• Code
• Ch4 server code

8
Holder Type for out and inout parameters

shorterHolder minute
Holder Object
public short value
9
Extending the Hello Example

• string hello(out short hour, out short minute)