As part of this four-part series on enterprise CORBA development, in this article, I begin exploring J2SE (Java 2 Platform, Standard Edition) 1.4's POA support. |
If you are just tuning in, we're in the midst of a four part series on the enterprise CORBA features included in J2SE (Java 2 Platform, Standard Edition) 1.4. Part 1 provided a whirlwind tour of those new features. That article ended with a quick Hello World example to set the stage for Part 2, which detailed the Portable Object Adapter (POA), introduced in CORBA 2.2 to replace the Basic Object Adapter (BOA). I also delved into the mechanics behind Part 1's Hello World example. In this article, I show how to apply the knowledge you've gained about the POA to create an enterprise-level application. In the process, we look at how the POA enables us to create high performance, and highly scalable and available applications. |
It turns out that CORBA solves these problems for us. CORBA provides a generalized way to "glue" objects together even if they're implemented in different languages and/or are physically distributed. A word of warning: CORBA is a very powerful and complicated beast. We'll only scratch the surface here, but with the techniques you learn in this column you'll have the fundamentals for using CORBA as a distributed computing mechanism for Java. |
Through the course of this article you will see that only one technology, CORBA, truly fulfills our wish list (and then some). In addition, you will see that because Java and CORBA are very complementary technologies, you can quickly and cost-effectively begin CORBA development in Java. |
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.) |
In my series on enterprise CORBA development using J2SE (Java 2 Platform, Standard Edition) 1.4, Part 1 served as a gentle introduction to CORBA and J2SE 1.4's enterprise CORBA features. Parts 2 and 3 provided a thorough treatment of the Portable Object Adapter (POA) and its role in creating enterprise applications that perform and scale with CORBA. In this concluding article, I discuss portable interceptors and the Interoperable Naming Service (INS). Portable interceptors provide standard hooks into the ORB (object request broker) runtime and offer a mechanism for plugging in additional ORB behavior or even modifying existing ORB behavior. The Interoperable Naming Service (INS) is a URL-based naming system built on top of the CORBA Naming Service. It specifies a common bootstrap mechanism that lets applications share a common initial naming context across ORB vendor providers. |
The final purpose of this article is to simulate pass-by-value in CORBA, obviously in the case that both server and client are developed in Java, without using OBV and RMI-IIOP. I'm going to build a component which transfers the class bytecode from the server to the client application. To achieve this, first you have to figure out how CORBA works and in which way it can transfer an object by reference. I will show this by using an example. Afterwards, using the same example, I will implement an application simulating pass-by-value of objects and, consequently, the local method invocation. |
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Similar to RMI, CORBA objects are specified with interfaces. Interfaces in CORBA, however, are specified in IDL. While IDL is similar to C++, it is important to note that IDL is not a programming language. For a detailed introduction to CORBA, please see Distributed Programming with Java: Chapter 11 (Overview of CORBA). |
- CORBA Specification (OMG) - Distributed Programming with Java book (Chapter 11: Overview of CORBA): - Java IDL Documentation - Distributed Java Programming with CORBA and RMI - New Features in CORBA 3.0 - Changes in CORBA Features between J2SE 1.3 and 1.4 |
Code sample 4: request.html Servlet <->CORBA Servlet <==> CORBA Communication |
To accurately evaluate the performance of J2EE Component-CORBA interoperability, the testing framework used was based on the architecture shown in Figure 3. Control of the test is handled by the client, which runs the test application described in the following section. All of the CORBA communication functionalities are encapsulated in the adapter object, facilitating the correspondence between our EJB, which is a stateful session bean, and the CORBA server. The CORBA server binds to the naming service, which may then be looked up by the J2EE component. |
The latest release of the Apache Geronimo server, M5 (Milestone 5; see Resources for a link), contains enhancements in the area of interoperability with external systems using CORBA. If you're already initiated into CORBA, you know the importance of this capability and how it may affect the viability of a J2EE server for a particular project. |
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Brad Rubin guides you through the basics of distributed computing, which lets you maximize computing potential with data sharing, improved performance, and enhanced function placement. He covers RMI and CORBA, showing how they are implemented in the Java? programming language, and uses plenty of code examples to illustrate the concepts. |
The management of a corporate information-systems department can foster excess law or liberty. An example of overextended laws would be the managerial directive to work with only one vendor, thereby exposing your systems to problems of extension or integration with potential corporate partners. With too many liberties, individuals or development groups are left to their own devices to pick technology that will again become difficult to extend or integrate if these technical gurus move on to "greener" stock options. One could be subject to the whims of a business environment. |
Burlington, MA, USA -- 08 August, 2001 -- PrismTech, a leading vendor of standards-based Integration Server technologies, today announced that it would be leading a submission to the OMG(TM)'s recently issued Request for Proposals (RFP) to integrate the CORBA(R) Notification and J2EE(TM) JMS Messaging Standards. PrismTech was also the primary author of the RFP itself. |
This is the third article in a four-part series to be concluded next week. Part 1: " Best practices in distributed object application development: RMI, CORBA and DCOM ." Part 2: Distributed Object Application Development: The Java-RMI Solution ." |
The Java 2 (formerly JDK 1.2) platform supports CORBA through Java IDL (Interface Definition Language) [1]. CORBA is an industry-standard middleware protocol that helps developers build distributed applications. The addition of CORBA as a standard component greatly enhances Java support for these cutting-edge apps. |