Patterns: Implementing Self-Service in an SOA Environment

Chapter 7. Application and system design guidelines 151

򐂰 Complete separation of the View-specific logic from the business logic, for

example, currency conversion based on the user preference.

򐂰 Using inheritance can promote view bean reuse and ensure that similar

information is received by all users, for example, CSRs and customers.

򐂰 View beans can be used with tools such as Rational Developer or IBM

WebSphere Studio Application Developer, which allows a developer to insert

JavaBean properties into JSPs.

򐂰 JSPs and associated view beans can be exhaustively unit tested by the View

developer prior to integration with the rest of the application.

On the other side, it is important to recognize the following disadvantages of

introducing result beans and view beans:

򐂰 View beans are tightly coupled with display pages and interaction controllers.

This implies that any changes to the dynamic content of the display page will

require a change to the interaction controller. We depend on the interaction

controller to gather all the required information in one view bean.

򐂰 For small applications, the introduction of view beans could result in too many

individual pieces of code and could increase the complexity of application

management.

򐂰 The number of artifacts to be coded, managed, and maintained will be

increased.

7.2.4 Formatter beans design pattern

The view bean concept described in the previous section tries to minimize the

need for inserting Java code directly inside a display page. In order to insert

complex tables or drop-down lists, complex conditional loops may be needed.

JSP API 1.1 does not define repeat tags that allow for looping through an

indexed JavaBean property. One option to overcome this is to implement the

complex table or drop-down list generation in Java and wrap it inside a bean.

Such reusable beans are called

formatter beans.

To summarize, a formatter bean is a bean that wrappers reusable HTML

formatting logic inside a method.

Advantages and disadvantages of formatter beans

Some advantages of formatter beans are:

򐂰 Eliminates the need for inserting complex scripting logic inside a JSP.

򐂰 Promotes reusability of the formatting logic.

򐂰 Hides the complexity of scripting logic from view designers.