tailieunhanh - professional java user interfaces phần 7

và năng động. Một lựa chọn rẻ hơn là để chính thức hóa các quy tắc kinh doanh với một khuôn khổ OOP nhẹ được nhúng vào phần còn lại của ứng dụng khách hàng và cung cấp một số hình thức của cơ chế 'không deployment6'. Tách logic kinh doanh trong các gói hoặc các lớp học được chia sẻ với các cơ sở mã máy chủ. | 368 Web-Based User Interfaces The Tuscan Jam Factory our award- winning marmalade figs onions spread orange jam plum cookies etruscan haggis olive oil Products Purchase Customers Resources Figure Too compact a navigation design Implementing Web applications with Java This section discusses the main technologies available for implementing Web GUIs with Java. Before going into details it briefly introduces the big picture in current architectures for Web GUIs. The typical architecture of a Web application One of the most striking differences in building Web interfaces using Java technology rather than applications is the fact that Web pages are defined in nonobject-oriented languages. This results in an impedance mismatch between the presentation technology and the remainder of the code that is implemented with Java classes and other languages similar to that created by relational databases. Web presentation also impacts GUI interaction which usually results in GUIs with a lower level of user interaction than for desktop application GUIs such as lack of features like drag and drop undo and so on. In Web GUIs event-based communication is usually needed less because Web clients usually provide less interactive features for users which is reflected on the server-side implementation. Furthermore additional care is devoted to simplifying the generation of the GUI in the markup language of choice and the content assembly of different areas of the GUI. A Web GUI typically communicates with a Web server submitting HTTP requests that the Web server forwards to other parts of the Web application. Such requests contain the session state and the data related to the current request. Although many arrangements are possible the Web server is usually part of a Web tier in a J2EE architecture interacting with the business and enterprise information system tier. Design details of Java Web applications can be found in countless books such as Alur Crupi and Malks 2001 for J2EE