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Trail: IDL
Lesson: Introducing Java IDL

What is Java IDL?

Java TM IDL is a technology for distributed objects--that is, objects interacting on different platforms across a network. Java IDL is similar to RMI (Remote Method Invocation), which supports distributed objects written entirely in the Java programming language. However, Java IDL enables objects to interact regardless of whether they're written in the Java programming language or another language such as C, C++, COBOL, or others.

This is possible because Java IDL is based on the Common Object Request Brokerage Architecture (CORBA), an industry-standard distributed object model. A key feature of CORBA is IDL, a language-neutral Interface Definition Language. Each language that supports CORBA has its own IDL mapping--and as its name implies, Java IDL supports the mapping for Java. CORBA and the IDL mappings are the work of an industry consortium known as the OMG, or Object Management Group. Sun is a founding member of the OMG, and the Java IDL team has played an active role in defining the IDL-to-Java mapping.

To support interaction between objects in separate programs, Java IDL provides an Object Request Broker, or ORB. The ORB is a class library that enables low-level communication between Java IDL applications and other CORBA-compliant applications. If this is starting to seem like alphabet soup, hold on: background details on CORBA, IDL, and the ORB are coming up in the next section.

This trail walks you through designing and developing a simple pair of interacting Java IDL applications. It starts by showing you the general architecture of CORBA, then follows with an overview of the steps to building CORBA applications in Java IDL. Finally, it takes you through each step to produce a running server and client that interact using CORBA.


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