WWW: Beyond the Basics

20 Common Object Request broker Architecture (CORBA)

20.12 WWW and CORBA

The chapter on WWW and distributed objects shows how distributed objects technology can help WWW.

Java applets have opened doors for running applications over the web. This opens innumerable opportunities for using distributed objects over the web. Java provides architecture neutrality and CORBA provides communication transparency.

Java system defines a standard semantics for bytecodes. Thus, java code guarantees the same functionality in all platforms. But java does not represent standard bit-pattern representation for objects and no protocol exists for transmitting arguments from one Java host to another or returning results. This is where CORBA ORB comes into picture. One of the primary function of CORBA ORBs is to marshall and unmarshall arguments for remote method invocation. Each CORBA displays an architecture-neutral interface and thus, local and remote method invocation are syntactically and functionally equivalent for CORBA objects differing only in performance.

Recently Sun has developed Java bindings to IDL. Thus, java objects can now interact with objects in corba compliant servers in the world. Thus for Java with a CORBA ORB, one needs to write an IDL specification for the remote objects, and the Java client communicates with them either via stubs generated by the IDL-to-Java compiler, or via the Dynamic Invocation Interface. Thus, to obtain results for the application, it can invoke methods in remote objects, pass parameters and obtain results. The client is transparent of the remote invocation of the methods. It does a call to a method as it does locally. CORBA's ORB takes care in finding the corresponding object and invoking the method and obtaining the results.

Java IDL provides a way for transparently connecting Java clients to network servers using the industry standard IDL Interface Definition language. The Java IDL system allows to define remote interfaces in the IDL interface definition language, which is an industry standard defined by the Object Management Group (OMG). This allows a Java client to transparently invoke an IDL object that resides on a remote server. Similarly, it allows a Java server to define objects that can be transparently invoked from IDL clients. [Sunsoft]

A typical application could be a java applet functioning as a front-end to an object database. The applet handles the graphical interaction with the user and invokes java methods on the objects in the database. The applet can furnish a far more flexible user-interface than that offered by HTML forms. [ Weiss ]

Another application is distributed library of objects in servers around the world. Any web application can utililize the functionality provided by these objects using CORBA. [ Weiss ]

Other possible applications include virtual classrooms, video conferencing and gambling. All these can make use of Java's internet connectivity and multimedia capabilities along with the functionality provided by objects written in other languages using CORBA.

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Padmapriya Vasudevan priya@csgrad.cs.vt.edu
Last modified: Sun Sep 22 21:16:15 1996