tailieunhanh - ECLIPSE WEB TOOLS PLATFORM developing java web applications PHẦN 4

Kiến trúc phần mềm và thiết kế phần lớn là một quá trình tham gia một hệ thống phức tạp và chia ra thành các hệ thống con nhỏ hơn, dễ quản lý hơn. Một trong các dòng quan trọng nhất của phân chia là phân tách các giao diện người dùng của một hệ thống từ cốt lõi của nó. Cốt lõi của một hệ thống thường được gọi là logic kinh doanh và giao diện người sử dụng như là logic trình bày. . | CHAPTER 7 The Presentation Tier The inmates are running the asylum. Alan Cooper Introduction Software architecture and design is largely a process of taking a complex system and dividing it into smaller more manageable subsystems. One of the most important lines of division is that which separates the user interface of a system from its core. The core of a system is often referred to as its business logic and the user interface as its presentation logic. We discussed the architectural aspects of this division previously in Chapter 5. We discuss WTP support for presentation logic in this chapter and for business logic in the next Chapter 8. The division between presentation and business logic is especially important in Web applications for two reasons. First the user interface is likely to change very frequently to improve its usability and to take advantage of new presentation technologies but the core is likely to be stable. For example in a banking system the core operations of transferring money between accounts or paying bills don t change much from year to year but the bank is very likely to continually improve its ease of use. If there is a clear separation between the presentation logic and the business logic then the presentation logic can be changed and tested much more quickly cheaply and reliably. Second if the business logic is independent of the presentation logic then it can be reused in other contexts and made available via other channels. For Web applications this means that the same business logic can be accessed for example by Web browsers voice response units and Web services. The set of components that implements the presentation logic of a Web 199 200 CHAPTER 7 The Presentation Tier application is referred to as the presentation tier. This chapter describes the structure of the presentation tier for Java Web applications and the tools in WTP for developing it. A large number of powerful technologies such as HTTP HTML CSS JavaScript XML XSLT .