Chapter 6. Enterprise Application Integration

Enterprise information systems—the collection of relational and legacy database systems, enterprise resource planning (ERP) systems, and mainframe transaction processing systems—provide the critical information infrastructure for an enterprise's business processes. These varied systems hold the information that an enterprise needs to carry out its daily operations. It is essential that new applications developed for an enterprise be able to integrate with these enterprise information systems (EIS).

EIS integration has always been of great importance, and this has given rise to enterprise application integration, or EAI. EAI enables an enterprise to integrate its existing applications and systems, plus it enables the addition of new technologies and applications. Enterprises must leverage their existing systems and resources even as they adopt new technologies. Considering the cost already invested in these existing systems, no business can afford to discard them. Plus, since these systems often contain valuable data needed by the enterprise, the enterprise is not likely to disrupt them. Yet, at the same time, enterprises continually grow and require new applications. To keep their businesses growing and to remain cost effective, enterprises must integrate their existing systems with these new applications and not replace existing systems with new applications written from scratch. The emergence of Web-based architectures and Web services adds impetus for enterprises to integrate their EISs and expose them to the Web.

The emergence of the Web and Web services is not the only factor driving the need for integration. More and more, enterprises are either merging or acquiring other enterprises. Such mergers and acquisitions usually entail merging and combining two divergent information technology (IT) systems. Not only are the IT systems different, but, as a further challenge, they each may have standardized on using different integration technologies within their respective environments. Emerging Web services standards are another factor driving Web services-based EAI. These standards are making it possible to integrate heterogeneous systems easily and cost effectively.

In today's environment, a typical enterprise has a multitude of existing applications running on diverse platforms and operating systems. Although these applications may very well rely on the same or similar data, they keep that data in different formats. Thus, the integration problem encompasses both data and system platforms.

These are but a few examples of the complexities that enterprise application integration must address. Not only must EAI handle integrating applications, it must also address integrating data and technologies so that enterprises can easily share business processes and data.

Using several scenarios, this chapter illustrates key integration considerations. It describes the J2EE 1.4 platform technologies that help with integration and presents some integration design approaches and guidelines.