This chapter discussed an imaginary company and its business, user, functional, and nonfunctional requirements, which drive the application. You will build this application throughout this book. Large portions of the application center on its ability to integrate with other businesses and applications through an external API and through, possibly, external user interface integration techniques.
You briefly saw the high-level architecture of the application and its structuring into an n-tier application that includes the client tier, Web tier, business logic tier, and persistence tier. Leading up to the decision to structure the application in this way, the chapter discussed two existing architectural patterns ”the Layers and N-Tier Architecture patterns ”and the J2EE architectural blueprint. The chapter expanded on the Web tier to discuss the two users of the Web tier ”users who access the tier through a presentation client and users who access the tier programmatically. The chapter also discussed how the business logic tier must facilitate both types of clients as well as the business object and business process content of the tier .
The architectural depiction of the application did not go to a deep level as the patterns presented in the next chapters will drive out more details of the architecture and design. Further, up until now you have worked with a high-level definition of Web Services and an implicit decision as to the use of Web Services throughout the application. The next chapters discuss the Web Service architecture using three patterns (the Service-Oriented Architecture, Architecture Adapter, and Service Directory patterns) and clear up the motivation and architecture details around embracing the Web Service architecture.