Patterns: Implementing Self-Service in an SOA Environment

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same outcome string: systemError. This string is then mapped to the generic

error page, SystemError.jsp, with a global navigation rule. Although a single error

page is not realistic for most complex applications, this does show how quickly

we can implement basic error handling in a JSF application.

9.3.5 Back-end interface

There are a number of patterns that can be used to integrate the JSF front-end

with the back-end of an application. These include the command bean pattern,

the business delegate pattern, session facade pattern, and data object pattern,

among others. In this redbook, we concentrate on the new JSF technology, as

well as the integration technologies used in the back end such as ESB, JCA,

JMS, and so forth. We did not want to spend much time on this particular layer,

and therefore chose to reuse classes from a larger ITSOMart ordering system, of

which our customer registration application is a subset.

The ITSOMart front-end to back-end interface follows the session facade design

pattern. The OrderSystemSessionFacade class offers coarse-grained services to

access the entity beans that store the customer data, and the message-based

credit check subsystem. It provides a simple remote interface for performing the

basic operations triggered by the front-end: create, retrieve, update, and delete.

9.4 Application development guidelines

Now that we have thoroughly discussed the high-level and low-level design

issues associated with the ITSOMart front-end, we will turn our attention to the

development aspects. Specifically, we highlight the use of Rational Software

Architect in building the application.

Note that given the scope of this redbook, we cannot expect to provide a

comprehensive user guide for building a JSF application using Rational Software

Architect. What we do instead, is touch on some of the key features, and see

how they are applied in the construction of our ITSOMart example. Instead of

describing every aspect of JSF development, we focus on the specific choices

and guidelines which drove the development of the ITSOMart front-end.

The complete ITSO front-end source code is available for download so we will

not attempt to walk through the entire process of constructing it from scratch.

See Appendix B, “Additional material” on page 485. We show, however, in depth

examples of how some of the key construction steps are performed.