Corba 3

Features

• Cover Type: Paperback with 626 pages
• Published by: Wiley Publishing May 1998
• Written in: English
• ISBN 10 Number: 0764532006
• ISBN 13 Number: 978-0764532009
• Book Dimensions: 9.5 x 7.2 x 1.5 inches
• Weighs: 2.2 pounds

Product Description
Build powerful client/server and Web applications that suit your professional requirements and add more muscle to your network with Corba, the latest technology to generate a strong buzz among Web developers and programmers. Although Corba has been around for quite some time, it has only recently become ready for mission-critical applications. Now there is a hands-on guide that goes beyond theory to show you what Corba can do.

Corba™ 3 features step-by-step instructions and practical examples that help the reader take advantage of this powerful technology. You get a complete background of Corba architecture, interface design, and IDL; guidelines for developing distributed architecture, writing code, and executing applications; techniques for handling dynamic invocation and the interface repository; a discussion of server threading models; extensive coverage of how Java and OODBMS work with Corba; and more.

The CD-ROM that accompanies Corba 3 includes JDK 1.1.5 as well as demo versions of IBM Visual Age for Java, IBM Web Runner, IONAs ORBIX 2, IONAs ORBIXWEB, and code samples from the book.

Excerpt. © Reprinted by permission. All rights reserved.


CORBA and Java

Excerpted from Chapter 9 of CORBA 3
by Reaz Hoque

Featuring: What Does CORBA Contribute to Java? How to Use CORBA with Java

Because the Web functions without Java, and Java exists without the Web, CORBA's contribution to Java can be separated from its contribution to the Web.

Java was originally envisioned as an enhancement to static Web pages; it has evolved, however, into an great option for enterprise applications (particularly on the client- side). As a result of this evolution, Java applications need to interoperate with back-end legacy systems in a scaleable, heterogeneous, and robust manner. While the stated shortcomings of CGI and the language homogeneity of Java's Remote Method Invocation (RMI) argue against use of these protocols, the robustness, platform and language neutrality, and flexibility of CORBA can bind Java into the enterprise.

How to Use CORBA with Java

Figure 9-2 illustrated the architecture of a simple application built on CORBA and Java using a Web browser to provide the client-side Java virtual machine. As with any Java- enabled Web page, when the client browser parses the Web page's APPLET tag, the lazy Java class loader downloads the minimum applet class files necessary to support the executing Java applet. Java class files (providing client-side ORB runtime functionality) may be included in this download sequence. Under other circumstances, the client-side ORB classes may have been installed on the client host as part of the Web browser installation, thereby eliminating a dynamic download of these classes. However, no prior need exists for ORB modules or executables to reside on the client's computer and enable the applet's CORBA-based communication back to the server. All necessary Java classes can be dynamically downloaded.

Once the applet is initialized and executing on the client machine, it establishes an ORB- based connection to one or more ORB-enabled servers residing on the same host as the Web server that served up the applet. The default behavior of the Java security manager necessitates this colocation of the Web server and the target ORB servers within the illustrated architecture. Under its default configuration, the Java security model prevents a dynamically downloaded applet from establishing a socket connection to a host from which it was not downloaded. (The mechanisms to overcome this restriction are discussed later in the chapter.)

With the applet executing and connected to the server, Java objects in the applet may begin invoking functions on any ORB-enabled objects in the server applications.

Several appealing aspects of this client/server interaction paradigm, both from the user's and the developer's prospective, follow:

Developers need only develop the client application once to execute on a multitude of platforms. Servers with IDL interfaces are accessible to any other enterprise applications in addition to the Web-based client. Intuitive, scaleable, and object-oriented implementation of the client to server communication. Minimal (or even zero) administration of the client host to support use of the client applet. A more intuitive programming model adds user functionality in a timely manner.

Using CORBA in combination with Java results in dynamic, adaptable, user-friendly, and developer-friendly software systems.

Reader Reviews
The book is very confusing. While the OMG bozos have done their best to make the CORBA as confusing as possible, the author doesn't even try to make it a bit more clear. All examples are given "as is" with the API explained in a "by the way" manner. The examples are VisiBroker oriented, yet the author doesn't even try to cover other ORBs and to give any hints on portable CORBA programming. I found the information flow very hectic and boring to read and the figures quite confusing (looks like more effort was spend on all those borders and shades). Finally, some examples are not indented (sic!), making them look like the winners from the Obfuscated C Contest. Conclusion: if you are considering purchasing this book - don't. Instead got for something from more reputable publishing houses (Prentice Hall or AW maybe).