This chapter provided an introduction to J2EE and using distributed components to create an application. We examined the various packages that are commonly associated with J2EE and examined the Web tier and business tier components in additional detail.
We saw that distributed components are logically organized into tiers, groups of components that generally have some physical or logical relation to one another. These logical tiers are an important part of the architectural process. They are used to set guidelines for the design of the components that comprise an application. In the architectural process, associating a component with a specific logical tier identifies the responsibilities of the component. These responsibilities in turn drive the detailed design of the component and will be used to identify the behaviors and members that will be assigned to the component.
We also examined the J2EE components that operate on these logical tiers. We provided a high level overview of the packages used to create these components, providing some details on how these packages originated and how they are developed using J2EE. Later sections will provide more detail and include examples of usage.
Now that we understand just what J2EE is, let's start at the beginning of the development process and discuss how a J2EE application should be designed. As with any complex technology, it is important to impart structure on the design process, otherwise what may result from the development effort would be an unworkable collection of components instead of a coherent, flexible application. The following chapters in this section will discuss the basic principles of the J2EE architecture and application design process.