Chapter 12: Legacy Integration: Performance Optimization

Legacy systems integration is a fast growing area of Java 2 Enterprise Edition (J2EE) application integration. In this chapter, you'll look at and pinpoint the areas within your WebSphere-based application and platform environment that can affect legacy systems integration.

Legacy Integration: What Is It?

The rapid emergence of the Internet and the "e-world" during the past decade split the legacy technologies from that of J2EE and Web-based technologies, such as Common Object Request Broker Architecture (CORBA), Common Gateway Interface (CGI), and so on. Specifically, a vast percentage of the world's large back-office systems were running legacy processing engines. Mainframes of all types and midframe systems such as VAXes and AS/400s, were commonplace during the mid-1990s.

With the Internet came entrepreneurs and people who saw the power in taking those back-office systems and interfacing them with the Web. Businesses further saw the power in providing customers with self-service capabilities such as online ordering and sales. Many of these systems were previously handled with proprietary and legacy systems that just weren't designed to cope with the volume transactions that the Web presented.

Legacy systems in companies before the Internet boom would work with loads of hundreds or, at the most, thousands of users. Also, most of this was from 8 a.m. to 6 p.m. The Internet threw all this out the door and provided a completely new paradigm for computing.

The Internet offers 24/7 operational and service availability and has user loads anywhere from the hundreds to the millions. Application computing has changed forever.

The problem we're faced with now is that companies want to get the most from their expensive, legacy, and sometimes proprietary systems. Companies, rightly so, don't want to throw away what has been working well for years . So, you're now faced with the challenge of integrating non-online systems such as mainframe and batch-based platforms into an environment that demands response times in milliseconds and works in the world of objects!

Many technologies are available that cater to this type of computing paradigm. Integrating a legacy system to a WebSphere-based application is no longer the nightmare it once was. Therefore, legacy integration is the act (art) of interfacing a WebSphere/J2EE-based application to a non-J2EE-based environment. Legacy refers to systems of older, sometimes less extensible, technology. One of the most common forms of legacy integration is where a WebSphere J2EE application is interfaced with a COBOL-based application on a mainframe via something such as MQ Series.

Figure 12-1 provides an example of a common integration of a legacy system with a WebSphere-based computing platform.

Figure 12-1: Example integration of a WebSphere/J2EE application with a legacy application

As you can see, at a high level, there's nothing complex about the topology. There are definitely many ways to approach this. What I'll discuss in this chapter isn't necessarily the topology considerations but the performance considerations of legacy integration. Remember that many legacy systems are asynchronous and, without proper consideration, will cause complete havoc with J2EE-based applications because of the threading and synchronous model that Java applications follow.