Distributed Java applications - Java/RMI and IDL/CORBA

It's quite possible to write interesting programs in the Java language without using any of the tools presented here. In fact, to write an application that runs locally on a machine, all you need to know is the language and a few simple packages.

However, as soon as the application needs to access databases or be distributed, it is necessary to be familiar with new tools offered in the Java environment. The aim of this article is to present these different tools and how they should be implemented. Of course, it is not possible to be exhaustive.

Distributed objects owe their success to networks, which have become simpler and faster for the user. It is now possible to make objects located on remote machines "live", and to have them communicate to cooperate in the success of a task whose components we know how to distribute.

Java offers two object distribution mechanisms:

• the Java/RMI ("remote method invocation") mechanism is specific to the Java environment. It enables communication only between Java language objects;

• the Java/IDL ("interface definition language") mechanism is the Java implementation of a more general, standardized mechanism called CORBA ("common object broker architecture"), enabling communication between Java objects and those defined in other languages.

We explain the particularities of these two mechanisms and give the basics on how to use them.