7.2 Self-Service application guidelines

The design guidelines outlined here primarily focus on Self-Service Web applications. Before exploring these guidelines, you should be familiar with the Self-Service runtime patterns and the various technology options available for implementing a Self-Service Web application, including server-centric Java-based technologies such as servlets, JSPs, JavaBeans, and EJBs for such implementations . The self-service basic concepts can be found in more detail in Chapter 3, "Selecting the Application patterns" on page 27.

Clients are responsible for accepting and validating the user input, communicating the user inputs to the Web application server, and presenting the results received from the Web browser, PDAs or WAP (for example cell phones).

Clients may use HTTP, IIOP, WAP, VoIP (Voice over IP), TCP/IP, or other Internet standard protocols to communicate with the Web application server. These clients can be broadly classified into the following categories:

HTML clients - These use HTTP protocol to communicate with the Web application server. These clients display HTML Web pages. In addition, they are capable of processing client-side JavaScript for enhancing navigation to perform simple input validation and to handle simple errors. Furthermore, the HTML clients can display small Java applets to enhance the GUI.
Application clients - These are primarily large Java applets or Java applications. These clients provide rich graphical user interfaces compared to HTML clients. They may communicate with the Web application server over a number of protocols including HTTP, IIOP, MQ, etc. Application clients communicate with the Web application server primarily to receive data rather than preformatted HTML pages. These clients use the data received to format and render the user interface. All of the user interface processing is performed on the client side. In addition, under this model, some parts of the business logic can also be processed on the client side.
Application clients that use Java Application for PDA using J2ME (Java 2 Micro Edition) -This application can be online or offline and can use the synchronization techniques using SyncML to update the data. In this case, the PDA should have a Java Runtime Environment (CVM, KVM, J9) and the appropriate configuration (CLDC - Connected Limited Device Configuration or CDC - Connected Device Configuration) and profile (MIDP, PDAP, etc.). Also in this case, the application will have some capabilities for processing.
WML clients - These use WAP protocols to communicate with the Web application server. These clients display WML in the client device. The communication between the gateway and Web application can be HTML using transcoding technologies to translate from HTML to WML; the application throws the data into XML format and certain software links it with a Stylesheet; WML can be directly provided by the application.