J2EE Design Patterns

Domain Objects

The patterns in this chapter focus on important aspects of business tier development. We start with the Domain Object Model, which is at the heart of most large J2EE applications. The Domain Object Model defines an object-oriented representation of the underlying data of an application. The benefits of this approach should be familiar by now: the tiers integrating with the business tier become simpler and are decoupled from the implementation of the business tier, allowing changes to the resource layer level implementation without affecting the UI components. Business processes can be included in the domain object model via methods attached to the entity objects in the model or to specialized objects.

We’ll also look at the Composite Entity pattern, which provides a guideline for building domain objects in an efficient way. The goal is to balance flexibility and efficiency by creating object representations that can be used in the most efficient way.

Domain Object Model

The domain model is the portion of the business tier that defines the actual data and processes managed and implemented by the system. The process for creating an effective domain model varies depending on the project, the information available, and the future requirements of the system.

The Domain Object Model pattern is central to most J2EE applications. The pattern is fundamentally simple: create a Java object model that represents the concepts in the underlying domain. This may seem obvious, and you ...