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J2SE 1.4 breathes new life into the CORBA community, Part 1

Get started developing enterprise CORBA applications with the latest version of J2SE

By Tarak Modi, JavaWorld.com, 08/30/02

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Over the past decade, CORBA, or the Common Object Request Broker Architecture, has lived up to its initial promise of providing developers an open, standard, and vendor-, platform-, and language-neutral specification for heterogeneous computing. Using the Internet Inter-ORB Protocol (IIOP), a CORBA-based program from any vendor, on most computers, operating systems, programming languages, and networks, can interoperate with a CORBA-based program from the same or different vendor, on most other computers, operating systems, programming languages, and networks. Similarly, Java has lived up equally well to its promise of providing Write Once, Run Anywhere portability, a highly productive implementation environment, and a robust platform. Is it any surprise then that the marriage between CORBA and Java is a match made in heaven?

This article, the first in a series of four, will begin with a brief history on the evolution of CORBA. I will then summarize the major additions to CORBA 2.3.1, the version that J2SE 1.4 supports. Finally, I will end the article with a whirlwind tour in which we'll create an application using CORBA and J2SE.

Read the whole series, "J2SE 1.4 Breathes New Life into the CORBA Community:"



A quick history lesson

In 1991, the Object Management Group (OMG) introduced CORBA 1.1, which defined the interface definition language (IDL) and APIs that enabled client/server object interaction within a specific implementation of an object request broker (ORB). CORBA 2.0, adopted in December 1994, took a major step forward and defined true interoperability between ORBs from different vendors via IIOP, which is the TCP/IP mapping of the General Inter-ORB Protocol (GIOP). CORBA 2.0 mandates that all compliant ORBs support IIOP to ensure interoperability.

Since then, CORBA has evolved slowly (the current version is 2.6.1), but each stage in that evolution has seen the addition of solid features geared towards creating scalable enterprise systems. Sun Microsystems started supporting CORBA in 1998 with the release of JDK 1.2 and the addition of Java IDL and a simple ORB. That began the long-lasting relationship between Java and CORBA. Today, four years later, J2SE 1.4 continues this marriage with support for CORBA 2.3.1. (As mentioned previously, the most recent version of CORBA is 2.6.1; its only significant difference from 2.3.1 is CORBA messaging, added in version 2.4.)

The basic CORBA architecture

Figure 1 shows the essence of a CORBA method invocation. As in most distributed systems, the client references a server application's (or object's) proxy. In CORBA, that proxy is called a stub. The client interacts with this stub as if it were the server and makes method invocations on it. The stub passes the request to the ORB, which, in turn, locates the server application, activating it if necessary. The ORB interacts with the server application through yet another proxy called a skeleton. Ultimately, the server application processes the client request, and the results return to the client through the same chain.

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