What initially drew me to application server technology was the need to support constantly changing, complex business rules. Traditional two-tiered client/server worked well for data intensive applications, but as the processing requirements grew, it became difficult to create and manage large client-based programs that supported these complex requirements. Moving the business logic to centralized application servers simplified both software development and code distribution.

Today's business applications are expected to move far beyond simple data management chores, performing business intelligence and decision support tasks for all levels of the company. Business requirements are also constantly changing, with new products and processes introduced in ever-shorter business cycles. Applications must not only encapsulate existing business logic, but be structured openly to allow quick response when rules change.

Business rule processing takes on a variety of forms, from simple data validation to complex data classifications and business processing logic. Encapsulating these processes in program code that can respond to changing requirements is a challenging task. Often, implementing rule processing around data structures instead of program code enables more flexibility and ease of maintenance. Commercial business rule processors and languages can also make the task easier to manage.

This chapter will examine how to incorporate complex business rules and processing into the application server environment. It will examine what a business rule is, how to implement the rules in program code, where to place the logic within the application architecture, and how to standardize error handling and reporting. Application security will also be examined, both as an application server issue and as a way of illustrating how to implement complex business rules.